摘要:

112 FRANCIS AND WHEELER THE OXIDATION OF XX.-The Oxidation of Banded Bituminous Coal at Low Temperatures. Studies in the Composition of Coal. By WILFRID FRANCIS and RICHARD VERNON WHEELER. OF the methods that have been used for studying the chemical composition of coal attack by reagents has not in general yielded much information. The majority of the reagents used have been oxidants such as nitric acid or Schultze’s solution and these either yield intractable gelatinous substances-the ulmins and their substitution products-or ultimately fatty acids usually oxali BA4NDED BITUMINOUS COAL AT LOW TEMPERATURES. 113 acid. The use of a milder oxidant such as atmospheric air a t lorn temperatures enables progressive changes in the character of the coal-substance to be studied and apart from the importance that a study of the Oxidation of coal by air h s s in relation to its spon-taneous combustion many of the observations made throw light on the character of some of the ingredients of coal and thus help towards an understanding of its constitution.The atmospheric Oxidation or " weathering " of coal has been found to increase the proportion of substances extractable by alkaline solutions-the ulmin compounds-or even to produce such substances where apparently none existed previously. For esaniple Dennstedt a i d Bunz (2. ungczc. Chem. 1905 25 1825), by heating a number of finely-powdered coals in open vessels during several days a t 130-150" showed that the effect of oxidation was, in some instances to prociizce as much as 30 to 36qb of illinin conipxnds.Jlahlcr (dnn. Mines 1913,4 163) pzsscd a slonr stream of air during long periods through coal heated a t low temperatures and found that traces of formic acid niethyl alcohol and acetone, and larger quantities of acetic acid were present in the condensed products of oxidation whilst the coals trheinselves became increas-ingly soluble in aqueous potassium hydroxide and their temperatures of initial decomposition decreased as oxidation proceeded. Ii the temperature at which oxidation was effected was higher than 250", the ulmin compounds (soluble in potassium hydroxide) formed at lowcr temperatures began to decompose. The present research has as its object the tracing of the changes that take place in the character and composition of the coal con-glomerate as oxidation slo~-ly proceeds ; and more particularly, the comparison of the behaviour of the macroscopically distinct ingredients into which most bituminous coals can readily be separ-ated when subjected to similar treatment.For inasmuch as these Laiided ingredients which Stopes has provisionally named vitrain, clarnin durain and fusain (Proc. Roy. Xoc. 1919 B 90 470) have been shown to possess markedly different chemical charactcristics even when taken from contiguous portions of the same lump of coal (see Tideswell and Wheeler J. 1919 115 619; Baranov and Francis Fuel 1922 1 219) an intimate study of the chemistry of '' coal " must of necessity treat of each ingredient separately ; whilst a comparison of the differences that exist between the ingredients which together form the coal as il; occurs in nature throws light on the manner of its formation.The coal chosen for this work was from the Top Hard seam at the East Kirkby Colliery LYottinghamshirc a detailed examination of which has been recorded by Baranov mid Francis (Eoc. cit.) 114 FRANCIS AND WHEELER THE OXIDATION OF The vitrain clarain and durain bands in this coal are sharply differ-entiated and it contains a fair proportion of fusain. No experi-ments were made with the clarain portion since previous work led us to believe that the results would be intermediate between those for the vitrain and durain portions. The method of experiment was briefly to draw a slow current of moist air through weighed samples (50 g.) of the three ingredients in the form of powder (through a 60's and on a 90's sieve) contained in glass tubes which could be maintained at a constant temperature during prolonged periods.After passing through the coal the air bubbled into a measured volume of cold distilled water to condense any liquid or soluble gaseous products. At stated intervals this water was examined and changed and a small fraction (5 g.) of each coal was removed from the tubes for analysis. Oxidation at 100". Liquid and Gaseous Products.-The treatment of the coals with air at 100" was carried out in four stages the first of two months' and the remainder each of 1 month's duration. The distilled water through which the air bubbled after leaving the coals had in each instance acquired a milky appearance* by the end of the first period and had increased in volume.Tests were made for alkalinity or acidity formaldehyde acetone acetaldehyde and methyl and ethyl alcohols. The chief results expressed approximately as per-centages on the coals are recorded in Table I. TABLE I. Formaldehyde Vitrain Methyl alcohol Acids Formaldehyde Acids Durain Methyl alcohol Formaldehyde Acids i { Period I (two months). 0.007 0.014 0.040 0.002 0.014 0-004 nil 9 9 9. Period I1 (one month). 0.01'7 0.006 0.006 0.010 0.002 trace 0.010 0.004 trace Period I11 (one month). 0*007 nil trace nil trace nil trace ?? 91 Period IV (one month). nil 7 9 9 9 9 9 9 9 7 ) 9 9 ? 9 9 9 None of the solutions contained acetone or acetaldehyde nor could any trace of ethyl alcohol be detected.The acids appeared to be either formic or acetic acid; sulphurous acid which might have been derived from pyrites or sulphur compounds in the coals, was absent nor was the acidity due to carbon dioxide in solution. The production of formaldehyde and methyl alcohol was not * This was found to be due to bacterial growths presumably derived from the coals ; it disappeared during subsequent periods of the oxidation BANDED BITUMINOUS COAL AT LOW TEMPERATURES. 115 continuous the liquids in the wash-bottles after the fourth oxidation period remaining apparently pure water ; we believe that they were produced from methane occluded in the coals probably by the action of ozone formed as the air bubbled through the wash-bottles leading to the coal samples.Changes in the Coal Substance during Oxidation.-The examina-tion of the samples withdrawn a t each period during the oxidation included proximate analyses of the usual type and by means of solvents and ultimate analyses. The results are surnrnarised in 1-i train Original 'Xoisturo 7; 9-58 Ash 1.14 Volatile matter (yo on ash-free dry coal) 30-74 Calcrific value (cals. ~ Per g.1 7940 'Moisture Ash Yo Durain Volatile ma,tter (7; on ash-free dry coal) Calorific value (cals. Per 6.) I Moisture "/b Ash yo ! ash-free dry coal) Calorific value (cals. I per g.) Volatile matter (yo on 3-58 4-08 28-91 7465 l.G6 17.7s 19.84 G4GG Period I.0.02 1.3i 31.01 6969 0.02 4-06 26-56 6973 0.10 17-57 23-69 597s Period 11. 0.us 1.6G 30.69 6615 0-35 3.95 25-00 6697 0.32 17-76 22.27 5s0 1 Period 111. 0.71 l - i B 31.16 6345 0-93 3-50 27-05 6530 0.92 17-80 20.98 57'70 Period IT. 0.98 1-76 31.06 6266 0.78 3-95 27-04 6515 0.90 17.96 20.78 6750 The original moisture in the coals was driven off during the first period of oxidation and thereafter each ingredient showed an increasing tendency to retain water or to absorb it rapidly from the air behaviour charactreristic of coals that are naturally of high osygen-content'. The resuhs of the '' volatile matter " determin-ations indicate differences in the character of the oxidation of the different portions of the same seam of coal the fusain and the ciurain presenting a peculiar contrast.The fusain showed an increase in the amount of volatile matt'er after the first period c,f Oxidation but the amount diminished as oxidation proceeded, assuming a nearly constant value higher than that of the original material; whilst with the durain there was a marked decrease at first and then a gradual increase to a constant value less than that of the original coal. With vitrain the values remained constant within the limits of experimental error with perhaps a tendency towards a slight increase. The vitrain was the only one of the thre 116 FRANCIS AND WHEELER THE OXIDATION OF ingredients that coked strongly before oxidation and its coking-power was destroyed after the fist period of heating.It will be noticed that the vitrain suffered the greatest depreciation in calorific value. TABLE 111. Analyses by Solvents. Oxidation at 100". Period Period Period Period Original. I. 11. 111. IV. a-Compounds 79-70,/ 85.6% 85.4% 87.6% 87.6% Vitrain /3-Compounds 14-6 10.4 11.0 9.6 9.9 y-Compounds 5.7 4.0 3.6 2.8 2.5 Clmins 0.02 11.17 11.25 11.3 11.2 a-Compounds 90-5 90.0 90.0 87-9 87.6 y-Compounds 2.7 2.95 - 2.9 3.0 { { Durain { j3-Compounds 6.8 7.05 - 9.2 9.4 Ulmins 0.01 2.6 5-58 6.6 6.52 a-Compounds 95.2 95.20 96-54 95.0 94.18 y -Compounds 1.4 1.45 - 1.6 1 *40 TJlmins nil 1.2 1.8 1.7 2.2 Fusain jI-Compounds 3.4 3.36 - 3.5 4.45 E'or convenience the nomenclature proposed by Stopes and Wheeler (" The Constitution of Coal," H.M.Stationery Office 1918), which makes no presumptions as to the nature of the fractions obtained by means of solvents has been employed " a-compounds " signifying that portion of coal insoluble in pyridine at its boiling point " p-compounds " that portion soluble in pyridine but iii-soluble in chloroform and '' y-compounds " that portion soluble both in pyridine and chloroform.* The term " ulmins " signifies those compounds in the coal as a whole that were soluble in alcoholic potassium hydroxide. The most striking charges on oxidation have occurred with the vitrain. Soluble ulmins were formed rapidly the change by oxid-ation at 100" being apparently complete at the end of the first period of heating and simultaneously about 30% of both the p- and y-com-pounds (amounting to 674 of the coal) was destroyed.The p-com-pounds obtained from the original coal formed a chocolate-brown powder whilst those from the oxidised coal appeared as brown nodules of dried jelly similar to the ulmins. It seemed probable, therefore that the p-compounds from the oxidised vitrain contained a relatively large proportion of the ulmins. The quantities of material available from this series of experiments did not permit of testing this assumption directly but i t was found that the 87.6% of a-compounds only contained about half the ulmins produced. * The a- 8- and y-compounds as thus defined are not necessarily similar in character in the oxidised and unoxidised coals BANDED BIT~~WINOUS COAL AT LOW TEMPERATURES.117 The 9.9% of &compounds recorded as being present in the oxidised coal must therefore be regarded as largely ulmified. With both the durain and the fusain the changes on oxidation were not so great as with the vitrain smaller amounts of ulrnins were produced and there was a tendency for the amounts of p-compounds (probably ulmified) to increase as oxidation proceeded. TABLE IV. (Expressed as percentages on the ash-free dry substances.) Ultimate Analyses. Oxidation at 100". Carbon Hydrogen Vitrain Oxygen Nitrogen Sulphur Carbon Hydrogen Nitrogen Durain Oxygen Sulphur Carbon Hydrogen Fusain \-Nitrogen 'Oygen Sulphur i i Original. 79.7 5.2 12.1 1.7 1.3 81.7 4.8 11.3 1.6 0.6 85.9 3.9 8-4 1.3 0-5 Period I.74.3 4.1 18.6 1.6 1.4 77.6 3.9 16.3 1-4 0.8 83.1 3.5 11.6 1.2 0-6 Period 11. 72-2 3.9 21.2 1-6 1.1 76.1 3.7 17.8 1.4 1.0 81.3 3.2 13.6 1.3 0.6 Analyses of d7ompounds. Carbon Oxygen etc. Carbon Oxygen etc. Carbon Oxygen etc. Vitrain Hydrogen 1' i Durain Hydrogen Original. 7 8.0 4.8 17-2 81.5 4.5 14.0 86.9 3.8 9.3 Period I. 73.2 4.1 22.7 75.5 3.7 20.8 83.5 3.4 13.1 Period 11. 73-2 3.8 23.0 75.9 3.7 20.4 82.2 3.2 14.6 Period 111. 71.9 3-8 21.3 1.8 1.2 '16.1 3.6 17-8 1.4 1.1 81.1 3.3 14-1 1.0 0.5 Period 111. 71.7 3.5 24.8 75.5 3.4 21.1 81.4 3.1 15.5 Period IV.72.1 3.8 21.1 1-8 1.2 76.5 3.7 17.1 1.5 1 *2 81.1 3.3 13.8 1.2 0.6 Period rv. 71.6 3.6 24.8 75.7 3.3 21-0 81.2 3.2 15-6 The vitrain durain and fusain from the original coal used showed the same gradations in analysis as were found by Tideswell and Wheeler for the Hamstead coal. During oxidation there was an increase of between 5 and 10% in the oxygen contents of each ingredient and a corresponding decrease in the carbon and hydrogen contents. With the vitrain since the proportion of a-compounds increased markedly on oxidation there was a tendency for their ultimate composition to approach that of the oxidised coal. The proportions of nitrogen and sulphur did not vary outside the limits of experimental error but the nature of the sulphur 118 FRANCIS AND WHEELER THE OXIDATION OF compounds present altered as is shown by determinations of " sulphate " sulphur as follows : TABLE V.Sulphur as Sulphates. Per cent. Original. Period I. Period 11. Period 111. Period IV. Vitrain nil 0.18 0.15 0.15 0-14 Durain 7 0.16 0.18 0.14 0.17 Fusain > 9 0.19 0.28 0.26 0.25 The sulphates were produced by the oxidation of pyrites originally present in the coal the fusain being the ingredient that contained most pyrites. A measure of the relative rates of oxidation of the three ingredients FIG. 1 . 1 2 3 Tirne-nwntb. can be obtained from the percentage increase in the amount of oxygen present in the samples withdrawn a t s u c c e s s i v e t i m e -intervals.The results are shown in Fig. 1 as graphs which closely resemble t'hose obtained in another manner by Tideswell and Wheeler for the rate of absorption of oxygen a t 100" by vitrain durain and fusain from Xamstead coal (J. 1920 117 '798, Fig. 3). Oxidation at 150". It was assumed that at the end of 5 months' treatment the action of oxygen on the coals a t 100" was complete an assumption warranted by the analytical data so far as the vitrain is concerned, but perhaps not quite correct with respect to the durain which as a whole was more resistant to attack. The remainder of each sample that had been oxidised at 100" during 5 months was now heated at 150" whilst moist air was drawn through. Heating was continued during 6 months samples of the coals being withdrawn a t intervals of 2 months and the liquids in the wash-bottles examined.Liquid and Gaseous Products .-The wash-bottle connected to the fusain sample contained only a solution of carbon dioxide but after each period of heating the solutions from the vitrain and durain samples were markedly acid (sulphurous acid) and containe BANDED BITUMIXOUS COAL AT LOW TEMPERATURES. 119 formaldehyde. The presence of acetone or methyl alcohol could not be detected. Changes in Weight.-During oxidation a t 100" the weight of each coal had a t first increased slightly and then decreased the h a 1 values being vitrain + 0.8 durain - 1.3 and fusain - 1.4% on the original weight. Oxidat<ion at 150" resulted in a progressive decrease in weight as is shown in Table V.TABLE V. Loss in weight on oxidation at 150". Per cent. Period I. Period 11. Period 111. Tota.1. Vitrain 8.8 7-3 0.2 16.3 Durain 4-6 5.5 3.0 13.1 Fusain 3.3 4.4 0.8 8.5 Changes in the Coal Substance.-The changes that took place in the character of the coals during oxidation at 150" are best appre-ciated by comparing the aiialytical data with those recorded for the final samples oxidised at 100". Each coal showed a marked increase in the amount of " volatile matter " and an increase in ash-content occasioned by the loss in weight of combustible matter. These results are recorded in Table VI. TABLE VI. Proximatte dnnlyses. Oxidation at 150". Final oxidation a t 100". Period I. Period 11. Period 111. Vitrain 31-0 40-7 40.4 40.5 Fusain 20.8 25-9 25.9 27.1 Vitrain 1-76 2.22 2-15 2.17 Durain 33-95 4.73 4-86 4-95 i Fusain 17.96 17.98 17.90 18.25 on ash-free dry Durain 27.0 31.8 32.1 32.2 substance % r Volatile matter Ash The most remarkable result of the oxidation at 150" was that the vitrain was rendered nearly completely soluble in alcoholic potass-ium hydroxide (compare Charpy and Decorps Compt.rend. 1921, 175 807) whilst the durain and fusain also contained greatly increased quantities of ulmins. The quantities together with the results of analysis by means of pyridine and chloroform are recorded in Table VII. It has been seen that oxidation a t 100" tended to dest,roy the compounds soluble in pyridine and t o a less degree those soluble both in pyridine and chloroform. Further oxidation at 150" apparently destroyed the y-compounds completely or at all events rendered them insoluble in chloroform; at the same time large 120 FRAXCIS AND WHEELER THE OXIDATION OF TABLE VII.Analyses by Solvents. Oxidation at 150". Final oxidation Period I. Period 11. Period 111. a-Compounds 87.6 75.9 57.7 55.0 9.9 23.2 42-3 45.0 y-Compounds 2.5 0.9 trace nil Ulmins 11.2 93.5 97.0 95.5 a-Compounds 87.6 87.4 80.3 77.0 Durain /3-Compounds 9.4 12.1 19.7 23-0 y -Compounds 3.0 0.5 trace nil Ulmins 6.5 36.1 43.5 46-0 94.2 94.5 82.0 80.0 a-Compounds 4-5 5-5 18.0 20.0 ni 1 y -Compounds 1.3 trace trace Ulmins 2.2 14-2 19.5 24.0 { proportions of the coals were rendered soluble in pyridine. It is doubtful however whether with these oxidised coals the degree of solubility in pyridine is of much significance since prolonged exposure of the coals to pyridine results in further extraction.TAELE VIII. Ultimate Analyses. Oxidation at 150". (Expressed as percentages on the ash-free dry substances.) Carbon Oxygen etc. Carbon Oxygen etc. Carbon Oxygen etc. Vitrain Hydrogen i { Durain Hydrogen Final oxidation at 100'. 72.1 3.8 24.1 76.5 3.7 19.8 81.1 3.3 15.6 Analyses 1 Carbon (Oxygen etc. Carbon Oxygen etc. Carbon Oxygen etc. Vitrain Hydrogen Period I. 66-4 2-7 30.9 71.9 2-5 25.6 77.8 2.4 19.8 of a-Compounds. 71.6 3.6 24.8 75.7 3.3 21.0 81.2 3.2 15.6 67.7 3.1 29.2 73-1 2.8 24.1 7 8.2 2.5 19.3 Period 11. 64-7 2.5 32.8 68.9 2-6 2 8-5 73-9 2.3 23.8 65-9 2.7 31.4 69-9 2.9 27.2 77.0 2.5 20-5 Period 111.64.9 2-3 32.8 67.0 2.3 30.7 74.2 2.2 23.6 64.9 2.3 32.8 75-2 2.3 22.5 Ultimate analyses were also made of some of the samples of ulmins produced on oxidation a t 150° as follows BANDED BITUMINOUS COAL AT LOW TEMPERATURES. 121 Carbon. Hydrogen. Oxygen etc. From vitrain. Period I. 64-8 2.8 32.4 From vitrain. Period I1[. 64.5 2.7 32-8 From vitrain. Period 111. 64.6 2.6 32.8 From durain. Period 111. 65.4 3-0 31.6 All these ulmins have similar analyses and the similarity extends to ulmins produced from the coals by oxidants other than air to which reference will be made later. With vitrain which was com-pletely ulmified by oxidation at 150" the analysis of the coal as a whole and that of the a-compounds contained in it were also similar.Thirty or more analyses of the fully oxidised vitrain have shown between 62 and 66% of carbon and between 2.6 and 3.5% of hydrogen. Some of these observed slight differences in analysis may be accounted for by the fact that the,ulmins are unstable compounds and suffer slight decomposition with elimination of water on prolonged heating at 150". It is apparent that marked changes have taken place in the coals during oxidation at 150". With vitrain almost the whole of the coal substance has been converted into alkali-soluble ulmins, wElst large proportions of both the durain and the fusain have been so converted. It is to this ulmin formation that the changes in the proximate and ultimate analyses and in the general character of the coals are due.The ultimate analyses show that the carbon content of the vitrain reached a minimum value owing to its almost com-plete conversion into alkali-soluble ulmins whilst the corresponding values for the durain and the fusain are higher because of the presence of substances more resistant to such ulmification or perhaps incapable of it. Oxidation at 200". Oxidation was continued at a higher temperature to find out whether complete ulmification of the durain and fusian would occur and to determine what changes if any would take place in the vitrain. The remaining portions of the samples heated at 150" were oxidised a t 200" during 1 month and examined.Each ingre-dient had lost about 25% in weight during this treatment with a corresponding increase in its percentage of ash. A k a l period of oxidation during a fortnight was then carried out. Analytical data are recorded in Table IX. firther ulmification of the durain had occurred but was by no means complete nor did it appear that more prolonged heating or heating at a higher temperature would be satisfactory for decom-position of the oxygenated coals (with the production of carbon dioxide and carbon monoxide) was taking place fairly rapidly. The ulmins produced from the vitrain a t 150" began to decompose (as is shown by the ultimate analyses) and were rendered partl 122 FRANCIS AND WHEELER THE OXIDATION O F Loss in weight yo Ash % Volatile matter (yo on ash-Ulmins Soluble in pyridine Carbon Hydrogen free dry substance) yo on ash-free dry sub-TABLE IX.Oxidation at 200". Vitrain. Period Period I. 11. 27.0 7.2 2-8 2.8 38.5 39.0 70.0 75.0 28.0 30.0 65.8 65.9 2-0 2.01 32.2 32.09 Durain. Period Period I. 11. 23.5 7.4 6.4 6.5 37.8 37.1 64-0 65.0 22.0 24.0 69.8 70-0 1-8 1.76 28.4 28.24 Fusain. Period Period I. 11. 19.7 7.0 21.4 21.6 29.8 31.2 20.5 22.0 11.0 13.0 72.8 71.3 1.8 1.6 25.4 27.1 insoluble in alcoholic potassium hydroxide ; indeed the solutions obtained were unlike those of the true ulmins being turbid and lack-ing the rich brown colour. So far as the vitrain is concerned the production of alkali-soluble ulmins must be regarded as having been completed by oxidation at 150".By carefully regulated oxidation it has thus been found possible to obtain from all the ingredients of the coal examined ulmins having similar analyses and properties and presumably derived from substances of the same nature that occur in different proportions in each ingredient. The vitrain consists almost entirely of these " reactive " compounds the durain contains a certain proportion of relatively " inert " substances and the fusain a greater proportion. These conclusions bear out and amplify the suggestion made by Tideswell and Wheeler (Zoc. cit. p. 633) that the difference chemic-ally between the vitrain clarain durain and fusain of a banded bituminous coal lies in the proportion of relatively " inert '' or unresponsive material with which the " reactive " portion is associated the " reactive " group of compounds being of the same chemical nature in each ingredient and containing more oxygen and less carbon than the " inert " material which may differ in character as between one ingredient and another.The present research specifies as the " reactive " group of compounds those that can be converted by oxidation into alkali-soluble ulmins. The " inert " substances are those that remain after a durain or a clarain has suffered all the ulmification possible by oxidation and i t would appear that they impart to the coal most of the specific qualities i t may possess. For examination of the residue from the durain after ulmification had been completed showed that i t consisted essentially of the plant entities (chiefly spore-exines) that originally resistant to the processes (bacterial and other) that resulted in the formation of the coal conglomerate still remained resistant to oxidation BANDED BITUMINOUS COAL AT LOW TEMPERATURES.123 This process of formation of alkali-soluble ulmins by oxidation (morc properly a process of regeneration) thus affords means which we have long sought of effecting a separation of the different plant entities from the coal mass and examining their chemical properties, according to the scheme outlined by Stopes and Wheeler (" The Constitution of Coal," H.M. Stationery Office p. 41). The process of oxidation by air at 150" is a long one and only admits of the troatment of small quantities of coal.We therefore made com-parat'ive experiments with other oxidants the action of which could-be regulated and found in hydrogen peroxide a reagent which if carefully uscd would rapidly effect the complete transformation of a vitrain into alkali-soluble ulmins and whilst rendering the bulk of a clarain or a durain soluble would leave their characteristic plant tissues substantially unaltered. The analysis of ulmins prepared by thc action of hydrogen peroxide on coal averages carbon 64.3, hydrogen 3.5 and oxygen 31.2% which is in close agreement with that of the similar compouiids produced by slow atmospheric oxidation a t 150". We have spoken of the formation of alkali-soluble ulmins from bituminous cod as a " regeneration." The solubility of the ulmin-compounds in alkaline solutions to form dark brown liquors is usually regarded as one of their chief characteristics and this property is used for their estimation.From estimations made in this way i t is found that the various groups of alkali-soluble ulmin-compounds form a large proportion of the " humus '' of decayed wood ; they occur sometimes in considerable quantities iii peats ; lignites also contain them but in normal bituminous coals they occur rarely, and then only in minute quantities whilst in anthracites their presence has never been detected. In other words the further the natural " carbonisation " or" the fuel has progressed the smaller is its content of soluble ulmins. From this i t is probable that the ulmin compounds once formed during the early processes of formation of the fuels have been subsequently so modified as to render them iunrecognisable by their solubility in alkalis.Berthelot and And& (Ann. Chirn. Phys. 1892 (vi] 25 420) observed that both ulmins formed artificially from sugar and those occurring naturally in soil began to decompose on exposure to air when moist carbon dioxide being evolved; Roger and Vulquin (Compt. rend. 1908 147 1404) made a similar observation on peat ulmins and noted also that they became insoluble in alkalis ; whilst Tidesm-ell and Wheeler have recorded in their study of dopplerite (J. 1922 121 2345) that this undoubted ulmin is less readily soluble in alkalis than that in more recent peats. Solubility in alkalis to form brown solutions should not therefore be regarded as a necessary property of th 124 THE OXIDATION OF BANDED BITUMINOUS COAL ETCL ulmins but it must be recognised that they can (through polymeris-ation and dehydration) change in character so as to lose their “ characteristic ” solubility.Neither the insoluble ulmins which we consider form the major part of newly-won bituminous coals nor the soluble ulmins regener-ated from them by oxidation are identical in character with those that form the major part of peat but they possess the same nuclear structure. The external groupings of the ulmin molecules in unoxidised coal are modified during oxidation the more easily detached groupings being eliminated to form simple oxygenated compounds whilst the residual ulmin becomes more definitely of acidic character (more so than the peat ulmins) owing to the form-ation of carboxylic groupings in place of those detached.Pearson (PueZ 1924 3 297) has reached similar conclusions to these as the result of his work on the oxidation of coals by sulphuric acid and bromine although the analyses of the ulmins so formed differ from ours (obtained either by atmospheric Oxidation or by the use of hydrogen peroxide) no doubt because chemical changes other than oxidation occurred during his experiments. Bituminous coal then consists essentially of insoluble ulmins in which morphologically organised plant tissues (that have escaped ulmification) are dispersed.” The present work shows that alkali-soluble ulmins can be regenerated from a bituminous coal by mild oxidation.If the coal is a vitrain i t consists almost solely of ulmins ; whilst the regeneration of alkali-soluble ulmins in a clarain, a durain or a fusain leaves residues characteristic of each of those ingredients which are essentially the original plant entities that were particularly resistant to or were preserved from the processes of “ decay ” that constituted the early stages of coal-formation and are apparently but little altered. The character of these residues is illustrated in Fig. 2 in which (a) and ( b ) are photomicrographs of cuticular tissues such as can be separated from a clarain by treatment with hydrogen peroxide and alcoholic potassium hydroxide ( c ) shows the exine of a megaspore, characteristic of the ddbbris from a durain obtained in the same manner and (d) a wood tracheid such as occurs in the ddbris of a fusain.Future communications will deal with the chemical * For the sake of simplicity we have here omitted discussion of the presence of natural plant-substances devoid of morphological organisation, such as “resin,” in the coal conglomerate. We have evidence that these resist oxidation at low temperatures and appear amongst the plant d&& after the process of regeneration of alkali-soluble ulmins by mean8 of hydrogen peroxide (or atmospheric oxidation). This work will be described in a forth-coming publication which deals also with the chemical properties of the regenerated Wins FIG. 2. ( a ) ancl ( b ) . Fragments of cuticular tissue characteristic plant entities in a clarain. ( a x 30 and b x 180.) ( c ) and ( d ) . The exine of a megaspore ( x 30) and a wood tracheid ( x 250), characteristic plant entities in 5t durain and a fusain respectively. [To face Trans. p . 124 TIDESWELL AND WHEELER ON FUSAIN AND ITS OXIDATION. 125 examination of similar plant-tissues separated in bulk from coal ; in particular with cuticles and spore-exines since these are so often the predominant structures to be found in clarains and durains, respectively and most bituminous coals consist mainly of clarain and durain. Work on modern cuticles and spore-exines for com-parison has already been in progress some years in the belief now justified that i t should be possible to isolate individual tissues or identifiable parts from coal so that for example any character-istic distillation products of which they are the source can be determined.DEPARTMENT OF FUEL TECHNOLOGY, SHEFFIJSD UNIVERSITY. [Received September 20th 1924. 112 FRANCIS AND WHEELER THE OXIDATION OF XX.-The Oxidation of Banded Bituminous Coal at Low Temperatures. Studies in the Composition of Coal. By WILFRID FRANCIS and RICHARD VERNON WHEELER. OF the methods that have been used for studying the chemical composition of coal attack by reagents has not in general yielded much information. The majority of the reagents used have been oxidants such as nitric acid or Schultze’s solution and these either yield intractable gelatinous substances-the ulmins and their substitution products-or ultimately fatty acids usually oxali BA4NDED BITUMINOUS COAL AT LOW TEMPERATURES.113 acid. The use of a milder oxidant such as atmospheric air a t lorn temperatures enables progressive changes in the character of the coal-substance to be studied and apart from the importance that a study of the Oxidation of coal by air h s s in relation to its spon-taneous combustion many of the observations made throw light on the character of some of the ingredients of coal and thus help towards an understanding of its constitution. The atmospheric Oxidation or " weathering " of coal has been found to increase the proportion of substances extractable by alkaline solutions-the ulmin compounds-or even to produce such substances where apparently none existed previously. For esaniple Dennstedt a i d Bunz (2. ungczc. Chem. 1905 25 1825), by heating a number of finely-powdered coals in open vessels during several days a t 130-150" showed that the effect of oxidation was, in some instances to prociizce as much as 30 to 36qb of illinin conipxnds.Jlahlcr (dnn. Mines 1913,4 163) pzsscd a slonr stream of air during long periods through coal heated a t low temperatures and found that traces of formic acid niethyl alcohol and acetone, and larger quantities of acetic acid were present in the condensed products of oxidation whilst the coals trheinselves became increas-ingly soluble in aqueous potassium hydroxide and their temperatures of initial decomposition decreased as oxidation proceeded. Ii the temperature at which oxidation was effected was higher than 250", the ulmin compounds (soluble in potassium hydroxide) formed at lowcr temperatures began to decompose.The present research has as its object the tracing of the changes that take place in the character and composition of the coal con-glomerate as oxidation slo~-ly proceeds ; and more particularly, the comparison of the behaviour of the macroscopically distinct ingredients into which most bituminous coals can readily be separ-ated when subjected to similar treatment. For inasmuch as these Laiided ingredients which Stopes has provisionally named vitrain, clarnin durain and fusain (Proc. Roy. Xoc. 1919 B 90 470) have been shown to possess markedly different chemical charactcristics even when taken from contiguous portions of the same lump of coal (see Tideswell and Wheeler J. 1919 115 619; Baranov and Francis Fuel 1922 1 219) an intimate study of the chemistry of '' coal " must of necessity treat of each ingredient separately ; whilst a comparison of the differences that exist between the ingredients which together form the coal as il; occurs in nature throws light on the manner of its formation.The coal chosen for this work was from the Top Hard seam at the East Kirkby Colliery LYottinghamshirc a detailed examination of which has been recorded by Baranov mid Francis (Eoc. cit.) 114 FRANCIS AND WHEELER THE OXIDATION OF The vitrain clarain and durain bands in this coal are sharply differ-entiated and it contains a fair proportion of fusain. No experi-ments were made with the clarain portion since previous work led us to believe that the results would be intermediate between those for the vitrain and durain portions.The method of experiment was briefly to draw a slow current of moist air through weighed samples (50 g.) of the three ingredients in the form of powder (through a 60's and on a 90's sieve) contained in glass tubes which could be maintained at a constant temperature during prolonged periods. After passing through the coal the air bubbled into a measured volume of cold distilled water to condense any liquid or soluble gaseous products. At stated intervals this water was examined and changed and a small fraction (5 g.) of each coal was removed from the tubes for analysis. Oxidation at 100". Liquid and Gaseous Products.-The treatment of the coals with air at 100" was carried out in four stages the first of two months' and the remainder each of 1 month's duration.The distilled water through which the air bubbled after leaving the coals had in each instance acquired a milky appearance* by the end of the first period and had increased in volume. Tests were made for alkalinity or acidity formaldehyde acetone acetaldehyde and methyl and ethyl alcohols. The chief results expressed approximately as per-centages on the coals are recorded in Table I. TABLE I. Formaldehyde Vitrain Methyl alcohol Acids Formaldehyde Acids Durain Methyl alcohol Formaldehyde Acids i { Period I (two months). 0.007 0.014 0.040 0.002 0.014 0-004 nil 9 9 9. Period I1 (one month). 0.01'7 0.006 0.006 0.010 0.002 trace 0.010 0.004 trace Period I11 (one month).0*007 nil trace nil trace nil trace ?? 91 Period IV (one month). nil 7 9 9 9 9 9 9 9 7 ) 9 9 ? 9 9 9 None of the solutions contained acetone or acetaldehyde nor could any trace of ethyl alcohol be detected. The acids appeared to be either formic or acetic acid; sulphurous acid which might have been derived from pyrites or sulphur compounds in the coals, was absent nor was the acidity due to carbon dioxide in solution. The production of formaldehyde and methyl alcohol was not * This was found to be due to bacterial growths presumably derived from the coals ; it disappeared during subsequent periods of the oxidation BANDED BITUMINOUS COAL AT LOW TEMPERATURES. 115 continuous the liquids in the wash-bottles after the fourth oxidation period remaining apparently pure water ; we believe that they were produced from methane occluded in the coals probably by the action of ozone formed as the air bubbled through the wash-bottles leading to the coal samples.Changes in the Coal Substance during Oxidation.-The examina-tion of the samples withdrawn a t each period during the oxidation included proximate analyses of the usual type and by means of solvents and ultimate analyses. The results are surnrnarised in 1-i train Original 'Xoisturo 7; 9-58 Ash 1.14 Volatile matter (yo on ash-free dry coal) 30-74 Calcrific value (cals. ~ Per g.1 7940 'Moisture Ash Yo Durain Volatile ma,tter (7; on ash-free dry coal) Calorific value (cals.Per 6.) I Moisture "/b Ash yo ! ash-free dry coal) Calorific value (cals. I per g.) Volatile matter (yo on 3-58 4-08 28-91 7465 l.G6 17.7s 19.84 G4GG Period I. 0.02 1.3i 31.01 6969 0.02 4-06 26-56 6973 0.10 17-57 23-69 597s Period 11. 0.us 1.6G 30.69 6615 0-35 3.95 25-00 6697 0.32 17-76 22.27 5s0 1 Period 111. 0.71 l - i B 31.16 6345 0-93 3-50 27-05 6530 0.92 17-80 20.98 57'70 Period IT. 0.98 1-76 31.06 6266 0.78 3-95 27-04 6515 0.90 17.96 20.78 6750 The original moisture in the coals was driven off during the first period of oxidation and thereafter each ingredient showed an increasing tendency to retain water or to absorb it rapidly from the air behaviour charactreristic of coals that are naturally of high osygen-content'.The resuhs of the '' volatile matter " determin-ations indicate differences in the character of the oxidation of the different portions of the same seam of coal the fusain and the ciurain presenting a peculiar contrast. The fusain showed an increase in the amount of volatile matt'er after the first period c,f Oxidation but the amount diminished as oxidation proceeded, assuming a nearly constant value higher than that of the original material; whilst with the durain there was a marked decrease at first and then a gradual increase to a constant value less than that of the original coal. With vitrain the values remained constant within the limits of experimental error with perhaps a tendency towards a slight increase.The vitrain was the only one of the thre 116 FRANCIS AND WHEELER THE OXIDATION OF ingredients that coked strongly before oxidation and its coking-power was destroyed after the fist period of heating. It will be noticed that the vitrain suffered the greatest depreciation in calorific value. TABLE 111. Analyses by Solvents. Oxidation at 100". Period Period Period Period Original. I. 11. 111. IV. a-Compounds 79-70,/ 85.6% 85.4% 87.6% 87.6% Vitrain /3-Compounds 14-6 10.4 11.0 9.6 9.9 y-Compounds 5.7 4.0 3.6 2.8 2.5 Clmins 0.02 11.17 11.25 11.3 11.2 a-Compounds 90-5 90.0 90.0 87-9 87.6 y-Compounds 2.7 2.95 - 2.9 3.0 { { Durain { j3-Compounds 6.8 7.05 - 9.2 9.4 Ulmins 0.01 2.6 5-58 6.6 6.52 a-Compounds 95.2 95.20 96-54 95.0 94.18 y -Compounds 1.4 1.45 - 1.6 1 *40 TJlmins nil 1.2 1.8 1.7 2.2 Fusain jI-Compounds 3.4 3.36 - 3.5 4.45 E'or convenience the nomenclature proposed by Stopes and Wheeler (" The Constitution of Coal," H.M.Stationery Office 1918), which makes no presumptions as to the nature of the fractions obtained by means of solvents has been employed " a-compounds " signifying that portion of coal insoluble in pyridine at its boiling point " p-compounds " that portion soluble in pyridine but iii-soluble in chloroform and '' y-compounds " that portion soluble both in pyridine and chloroform.* The term " ulmins " signifies those compounds in the coal as a whole that were soluble in alcoholic potassium hydroxide. The most striking charges on oxidation have occurred with the vitrain.Soluble ulmins were formed rapidly the change by oxid-ation at 100" being apparently complete at the end of the first period of heating and simultaneously about 30% of both the p- and y-com-pounds (amounting to 674 of the coal) was destroyed. The p-com-pounds obtained from the original coal formed a chocolate-brown powder whilst those from the oxidised coal appeared as brown nodules of dried jelly similar to the ulmins. It seemed probable, therefore that the p-compounds from the oxidised vitrain contained a relatively large proportion of the ulmins. The quantities of material available from this series of experiments did not permit of testing this assumption directly but i t was found that the 87.6% of a-compounds only contained about half the ulmins produced.* The a- 8- and y-compounds as thus defined are not necessarily similar in character in the oxidised and unoxidised coals BANDED BIT~~WINOUS COAL AT LOW TEMPERATURES. 117 The 9.9% of &compounds recorded as being present in the oxidised coal must therefore be regarded as largely ulmified. With both the durain and the fusain the changes on oxidation were not so great as with the vitrain smaller amounts of ulrnins were produced and there was a tendency for the amounts of p-compounds (probably ulmified) to increase as oxidation proceeded. TABLE IV. (Expressed as percentages on the ash-free dry substances.) Ultimate Analyses. Oxidation at 100". Carbon Hydrogen Vitrain Oxygen Nitrogen Sulphur Carbon Hydrogen Nitrogen Durain Oxygen Sulphur Carbon Hydrogen Fusain \-Nitrogen 'Oygen Sulphur i i Original.79.7 5.2 12.1 1.7 1.3 81.7 4.8 11.3 1.6 0.6 85.9 3.9 8-4 1.3 0-5 Period I. 74.3 4.1 18.6 1.6 1.4 77.6 3.9 16.3 1-4 0.8 83.1 3.5 11.6 1.2 0-6 Period 11. 72-2 3.9 21.2 1-6 1.1 76.1 3.7 17.8 1.4 1.0 81.3 3.2 13.6 1.3 0.6 Analyses of d7ompounds. Carbon Oxygen etc. Carbon Oxygen etc. Carbon Oxygen etc. Vitrain Hydrogen 1' i Durain Hydrogen Original. 7 8.0 4.8 17-2 81.5 4.5 14.0 86.9 3.8 9.3 Period I. 73.2 4.1 22.7 75.5 3.7 20.8 83.5 3.4 13.1 Period 11. 73-2 3.8 23.0 75.9 3.7 20.4 82.2 3.2 14.6 Period 111.71.9 3-8 21.3 1.8 1.2 '16.1 3.6 17-8 1.4 1.1 81.1 3.3 14-1 1.0 0.5 Period 111. 71.7 3.5 24.8 75.5 3.4 21.1 81.4 3.1 15.5 Period IV. 72.1 3.8 21.1 1-8 1.2 76.5 3.7 17.1 1.5 1 *2 81.1 3.3 13.8 1.2 0.6 Period rv. 71.6 3.6 24.8 75.7 3.3 21-0 81.2 3.2 15-6 The vitrain durain and fusain from the original coal used showed the same gradations in analysis as were found by Tideswell and Wheeler for the Hamstead coal. During oxidation there was an increase of between 5 and 10% in the oxygen contents of each ingredient and a corresponding decrease in the carbon and hydrogen contents. With the vitrain since the proportion of a-compounds increased markedly on oxidation there was a tendency for their ultimate composition to approach that of the oxidised coal.The proportions of nitrogen and sulphur did not vary outside the limits of experimental error but the nature of the sulphur 118 FRANCIS AND WHEELER THE OXIDATION OF compounds present altered as is shown by determinations of " sulphate " sulphur as follows : TABLE V. Sulphur as Sulphates. Per cent. Original. Period I. Period 11. Period 111. Period IV. Vitrain nil 0.18 0.15 0.15 0-14 Durain 7 0.16 0.18 0.14 0.17 Fusain > 9 0.19 0.28 0.26 0.25 The sulphates were produced by the oxidation of pyrites originally present in the coal the fusain being the ingredient that contained most pyrites. A measure of the relative rates of oxidation of the three ingredients FIG.1 . 1 2 3 Tirne-nwntb. can be obtained from the percentage increase in the amount of oxygen present in the samples withdrawn a t s u c c e s s i v e t i m e -intervals. The results are shown in Fig. 1 as graphs which closely resemble t'hose obtained in another manner by Tideswell and Wheeler for the rate of absorption of oxygen a t 100" by vitrain durain and fusain from Xamstead coal (J. 1920 117 '798, Fig. 3). Oxidation at 150". It was assumed that at the end of 5 months' treatment the action of oxygen on the coals a t 100" was complete an assumption warranted by the analytical data so far as the vitrain is concerned, but perhaps not quite correct with respect to the durain which as a whole was more resistant to attack. The remainder of each sample that had been oxidised at 100" during 5 months was now heated at 150" whilst moist air was drawn through.Heating was continued during 6 months samples of the coals being withdrawn a t intervals of 2 months and the liquids in the wash-bottles examined. Liquid and Gaseous Products .-The wash-bottle connected to the fusain sample contained only a solution of carbon dioxide but after each period of heating the solutions from the vitrain and durain samples were markedly acid (sulphurous acid) and containe BANDED BITUMIXOUS COAL AT LOW TEMPERATURES. 119 formaldehyde. The presence of acetone or methyl alcohol could not be detected. Changes in Weight.-During oxidation a t 100" the weight of each coal had a t first increased slightly and then decreased the h a 1 values being vitrain + 0.8 durain - 1.3 and fusain - 1.4% on the original weight.Oxidat<ion at 150" resulted in a progressive decrease in weight as is shown in Table V. TABLE V. Loss in weight on oxidation at 150". Per cent. Period I. Period 11. Period 111. Tota.1. Vitrain 8.8 7-3 0.2 16.3 Durain 4-6 5.5 3.0 13.1 Fusain 3.3 4.4 0.8 8.5 Changes in the Coal Substance.-The changes that took place in the character of the coals during oxidation at 150" are best appre-ciated by comparing the aiialytical data with those recorded for the final samples oxidised at 100". Each coal showed a marked increase in the amount of " volatile matter " and an increase in ash-content occasioned by the loss in weight of combustible matter. These results are recorded in Table VI.TABLE VI. Proximatte dnnlyses. Oxidation at 150". Final oxidation a t 100". Period I. Period 11. Period 111. Vitrain 31-0 40-7 40.4 40.5 Fusain 20.8 25-9 25.9 27.1 Vitrain 1-76 2.22 2-15 2.17 Durain 33-95 4.73 4-86 4-95 i Fusain 17.96 17.98 17.90 18.25 on ash-free dry Durain 27.0 31.8 32.1 32.2 substance % r Volatile matter Ash The most remarkable result of the oxidation at 150" was that the vitrain was rendered nearly completely soluble in alcoholic potass-ium hydroxide (compare Charpy and Decorps Compt. rend. 1921, 175 807) whilst the durain and fusain also contained greatly increased quantities of ulmins. The quantities together with the results of analysis by means of pyridine and chloroform are recorded in Table VII.It has been seen that oxidation a t 100" tended to dest,roy the compounds soluble in pyridine and t o a less degree those soluble both in pyridine and chloroform. Further oxidation at 150" apparently destroyed the y-compounds completely or at all events rendered them insoluble in chloroform; at the same time large 120 FRAXCIS AND WHEELER THE OXIDATION OF TABLE VII. Analyses by Solvents. Oxidation at 150". Final oxidation Period I. Period 11. Period 111. a-Compounds 87.6 75.9 57.7 55.0 9.9 23.2 42-3 45.0 y-Compounds 2.5 0.9 trace nil Ulmins 11.2 93.5 97.0 95.5 a-Compounds 87.6 87.4 80.3 77.0 Durain /3-Compounds 9.4 12.1 19.7 23-0 y -Compounds 3.0 0.5 trace nil Ulmins 6.5 36.1 43.5 46-0 94.2 94.5 82.0 80.0 a-Compounds 4-5 5-5 18.0 20.0 ni 1 y -Compounds 1.3 trace trace Ulmins 2.2 14-2 19.5 24.0 { proportions of the coals were rendered soluble in pyridine.It is doubtful however whether with these oxidised coals the degree of solubility in pyridine is of much significance since prolonged exposure of the coals to pyridine results in further extraction. TAELE VIII. Ultimate Analyses. Oxidation at 150". (Expressed as percentages on the ash-free dry substances.) Carbon Oxygen etc. Carbon Oxygen etc. Carbon Oxygen etc. Vitrain Hydrogen i { Durain Hydrogen Final oxidation at 100'. 72.1 3.8 24.1 76.5 3.7 19.8 81.1 3.3 15.6 Analyses 1 Carbon (Oxygen etc. Carbon Oxygen etc. Carbon Oxygen etc. Vitrain Hydrogen Period I. 66-4 2-7 30.9 71.9 2-5 25.6 77.8 2.4 19.8 of a-Compounds.71.6 3.6 24.8 75.7 3.3 21.0 81.2 3.2 15.6 67.7 3.1 29.2 73-1 2.8 24.1 7 8.2 2.5 19.3 Period 11. 64-7 2.5 32.8 68.9 2-6 2 8-5 73-9 2.3 23.8 65-9 2.7 31.4 69-9 2.9 27.2 77.0 2.5 20-5 Period 111. 64.9 2-3 32.8 67.0 2.3 30.7 74.2 2.2 23.6 64.9 2.3 32.8 75-2 2.3 22.5 Ultimate analyses were also made of some of the samples of ulmins produced on oxidation a t 150° as follows BANDED BITUMINOUS COAL AT LOW TEMPERATURES. 121 Carbon. Hydrogen. Oxygen etc. From vitrain. Period I. 64-8 2.8 32.4 From vitrain. Period I1[. 64.5 2.7 32-8 From vitrain. Period 111. 64.6 2.6 32.8 From durain. Period 111. 65.4 3-0 31.6 All these ulmins have similar analyses and the similarity extends to ulmins produced from the coals by oxidants other than air to which reference will be made later.With vitrain which was com-pletely ulmified by oxidation at 150" the analysis of the coal as a whole and that of the a-compounds contained in it were also similar. Thirty or more analyses of the fully oxidised vitrain have shown between 62 and 66% of carbon and between 2.6 and 3.5% of hydrogen. Some of these observed slight differences in analysis may be accounted for by the fact that the,ulmins are unstable compounds and suffer slight decomposition with elimination of water on prolonged heating at 150". It is apparent that marked changes have taken place in the coals during oxidation at 150". With vitrain almost the whole of the coal substance has been converted into alkali-soluble ulmins, wElst large proportions of both the durain and the fusain have been so converted.It is to this ulmin formation that the changes in the proximate and ultimate analyses and in the general character of the coals are due. The ultimate analyses show that the carbon content of the vitrain reached a minimum value owing to its almost com-plete conversion into alkali-soluble ulmins whilst the corresponding values for the durain and the fusain are higher because of the presence of substances more resistant to such ulmification or perhaps incapable of it. Oxidation at 200". Oxidation was continued at a higher temperature to find out whether complete ulmification of the durain and fusian would occur and to determine what changes if any would take place in the vitrain.The remaining portions of the samples heated at 150" were oxidised a t 200" during 1 month and examined. Each ingre-dient had lost about 25% in weight during this treatment with a corresponding increase in its percentage of ash. A k a l period of oxidation during a fortnight was then carried out. Analytical data are recorded in Table IX. firther ulmification of the durain had occurred but was by no means complete nor did it appear that more prolonged heating or heating at a higher temperature would be satisfactory for decom-position of the oxygenated coals (with the production of carbon dioxide and carbon monoxide) was taking place fairly rapidly. The ulmins produced from the vitrain a t 150" began to decompose (as is shown by the ultimate analyses) and were rendered partl 122 FRANCIS AND WHEELER THE OXIDATION O F Loss in weight yo Ash % Volatile matter (yo on ash-Ulmins Soluble in pyridine Carbon Hydrogen free dry substance) yo on ash-free dry sub-TABLE IX.Oxidation at 200". Vitrain. Period Period I. 11. 27.0 7.2 2-8 2.8 38.5 39.0 70.0 75.0 28.0 30.0 65.8 65.9 2-0 2.01 32.2 32.09 Durain. Period Period I. 11. 23.5 7.4 6.4 6.5 37.8 37.1 64-0 65.0 22.0 24.0 69.8 70-0 1-8 1.76 28.4 28.24 Fusain. Period Period I. 11. 19.7 7.0 21.4 21.6 29.8 31.2 20.5 22.0 11.0 13.0 72.8 71.3 1.8 1.6 25.4 27.1 insoluble in alcoholic potassium hydroxide ; indeed the solutions obtained were unlike those of the true ulmins being turbid and lack-ing the rich brown colour.So far as the vitrain is concerned the production of alkali-soluble ulmins must be regarded as having been completed by oxidation at 150". By carefully regulated oxidation it has thus been found possible to obtain from all the ingredients of the coal examined ulmins having similar analyses and properties and presumably derived from substances of the same nature that occur in different proportions in each ingredient. The vitrain consists almost entirely of these " reactive " compounds the durain contains a certain proportion of relatively " inert " substances and the fusain a greater proportion. These conclusions bear out and amplify the suggestion made by Tideswell and Wheeler (Zoc.cit. p. 633) that the difference chemic-ally between the vitrain clarain durain and fusain of a banded bituminous coal lies in the proportion of relatively " inert '' or unresponsive material with which the " reactive " portion is associated the " reactive " group of compounds being of the same chemical nature in each ingredient and containing more oxygen and less carbon than the " inert " material which may differ in character as between one ingredient and another. The present research specifies as the " reactive " group of compounds those that can be converted by oxidation into alkali-soluble ulmins. The " inert " substances are those that remain after a durain or a clarain has suffered all the ulmification possible by oxidation and i t would appear that they impart to the coal most of the specific qualities i t may possess.For examination of the residue from the durain after ulmification had been completed showed that i t consisted essentially of the plant entities (chiefly spore-exines) that originally resistant to the processes (bacterial and other) that resulted in the formation of the coal conglomerate still remained resistant to oxidation BANDED BITUMINOUS COAL AT LOW TEMPERATURES. 123 This process of formation of alkali-soluble ulmins by oxidation (morc properly a process of regeneration) thus affords means which we have long sought of effecting a separation of the different plant entities from the coal mass and examining their chemical properties, according to the scheme outlined by Stopes and Wheeler (" The Constitution of Coal," H.M.Stationery Office p. 41). The process of oxidation by air at 150" is a long one and only admits of the troatment of small quantities of coal. We therefore made com-parat'ive experiments with other oxidants the action of which could-be regulated and found in hydrogen peroxide a reagent which if carefully uscd would rapidly effect the complete transformation of a vitrain into alkali-soluble ulmins and whilst rendering the bulk of a clarain or a durain soluble would leave their characteristic plant tissues substantially unaltered. The analysis of ulmins prepared by thc action of hydrogen peroxide on coal averages carbon 64.3, hydrogen 3.5 and oxygen 31.2% which is in close agreement with that of the similar compouiids produced by slow atmospheric oxidation a t 150".We have spoken of the formation of alkali-soluble ulmins from bituminous cod as a " regeneration." The solubility of the ulmin-compounds in alkaline solutions to form dark brown liquors is usually regarded as one of their chief characteristics and this property is used for their estimation. From estimations made in this way i t is found that the various groups of alkali-soluble ulmin-compounds form a large proportion of the " humus '' of decayed wood ; they occur sometimes in considerable quantities iii peats ; lignites also contain them but in normal bituminous coals they occur rarely, and then only in minute quantities whilst in anthracites their presence has never been detected. In other words the further the natural " carbonisation " or" the fuel has progressed the smaller is its content of soluble ulmins.From this i t is probable that the ulmin compounds once formed during the early processes of formation of the fuels have been subsequently so modified as to render them iunrecognisable by their solubility in alkalis. Berthelot and And& (Ann. Chirn. Phys. 1892 (vi] 25 420) observed that both ulmins formed artificially from sugar and those occurring naturally in soil began to decompose on exposure to air when moist carbon dioxide being evolved; Roger and Vulquin (Compt. rend. 1908 147 1404) made a similar observation on peat ulmins and noted also that they became insoluble in alkalis ; whilst Tidesm-ell and Wheeler have recorded in their study of dopplerite (J.1922 121 2345) that this undoubted ulmin is less readily soluble in alkalis than that in more recent peats. Solubility in alkalis to form brown solutions should not therefore be regarded as a necessary property of th 124 THE OXIDATION OF BANDED BITUMINOUS COAL ETCL ulmins but it must be recognised that they can (through polymeris-ation and dehydration) change in character so as to lose their “ characteristic ” solubility. Neither the insoluble ulmins which we consider form the major part of newly-won bituminous coals nor the soluble ulmins regener-ated from them by oxidation are identical in character with those that form the major part of peat but they possess the same nuclear structure. The external groupings of the ulmin molecules in unoxidised coal are modified during oxidation the more easily detached groupings being eliminated to form simple oxygenated compounds whilst the residual ulmin becomes more definitely of acidic character (more so than the peat ulmins) owing to the form-ation of carboxylic groupings in place of those detached.Pearson (PueZ 1924 3 297) has reached similar conclusions to these as the result of his work on the oxidation of coals by sulphuric acid and bromine although the analyses of the ulmins so formed differ from ours (obtained either by atmospheric Oxidation or by the use of hydrogen peroxide) no doubt because chemical changes other than oxidation occurred during his experiments. Bituminous coal then consists essentially of insoluble ulmins in which morphologically organised plant tissues (that have escaped ulmification) are dispersed.” The present work shows that alkali-soluble ulmins can be regenerated from a bituminous coal by mild oxidation. If the coal is a vitrain i t consists almost solely of ulmins ; whilst the regeneration of alkali-soluble ulmins in a clarain, a durain or a fusain leaves residues characteristic of each of those ingredients which are essentially the original plant entities that were particularly resistant to or were preserved from the processes of “ decay ” that constituted the early stages of coal-formation and are apparently but little altered. The character of these residues is illustrated in Fig. 2 in which (a) and ( b ) are photomicrographs of cuticular tissues such as can be separated from a clarain by treatment with hydrogen peroxide and alcoholic potassium hydroxide ( c ) shows the exine of a megaspore, characteristic of the ddbbris from a durain obtained in the same manner and (d) a wood tracheid such as occurs in the ddbris of a fusain. Future communications will deal with the chemical * For the sake of simplicity we have here omitted discussion of the presence of natural plant-substances devoid of morphological organisation, such as “resin,” in the coal conglomerate. We have evidence that these resist oxidation at low temperatures and appear amongst the plant d&& after the process of regeneration of alkali-soluble ulmins by mean8 of hydrogen peroxide (or atmospheric oxidation). This work will be described in a forth-coming publication which deals also with the chemical properties of the regenerated Wins FIG. 2. ( a ) ancl ( b ) . Fragments of cuticular tissue characteristic plant entities in a clarain. ( a x 30 and b x 180. ) ( c ) and ( d ) . The exine of a megaspore ( x 30) and a wood tracheid ( x 250), characteristic plant entities in 5t durain and a fusain respectively. [To face Trans. p . 124 TIDESWELL AND WHEELER ON FUSAIN AND ITS OXIDATION. 125 examination of similar plant-tissues separated in bulk from coal ; in particular with cuticles and spore-exines since these are so often the predominant structures to be found in clarains and durains, respectively and most bituminous coals consist mainly of clarain and durain. Work on modern cuticles and spore-exines for com-parison has already been in progress some years in the belief now justified that i t should be possible to isolate individual tissues or identifiable parts from coal so that for example any character-istic distillation products of which they are the source can be determined. DEPARTMENT OF FUEL TECHNOLOGY, SHEFFIJSD UNIVERSITY. [Received September 20th 1924.

ISSN:0368-1645    

DOI:10.1039/CT9252700112

出版商:RSC    

年代:1925

数据来源: RSC

摘要:

TIDESWELL AND WHEELER ON FUSAIN AND ITS OXIDATION. 125 XX1.-On Fusain artd its Oxidation. Studies in the Cornpo&ion of Coal. By FREDERICK VINCENT TIDESWELL and RICIFARD VERNON WHEELER. SPONTANEOUS combustion in a seam of coal in so far as it may be determined by the chemical composition of the materials composing the seam originates with the most readily oxidisable ingredient thereof. Amongst mining men there is a belief the history of which it is unnecessary to trace that a frequent cause of spon-taneous combustion is the presence in the seam of fusain; * that fire actually originates in bands of fusain when such are present, and travels preferentially along them. Data regarding the rate of oxidation of a fusain have been supplied by Winmill (Trans. Inst. Min.Eng. 1913 46 563) who concluded that of all parts of the Barnsley seam which he examined in detail the fusain was the least capable of heating spontaneously. Our own experiments when using coal from the Hamstead Thick seam (J. 1920 117 794) gave quite different results. The vitrain, clarain and durain (the brilliant bright and dull portions of the seam) absorbed oxygen a t rates graded in the direction expected from previous work on the chemical constitution of these ingredients of banded bituminous coal (J. 1919 115 619) but the fusain stood apart. At 15" and 50" its absorptive power for oxygen was several times greater than that of the rest of the coal although at 100" it was of the same order. From this it can be concluded that the fuaain weight fcr weight is the most liable to self-heat (from * Sometimes called " mother of coal," " mineral charcoal," " dant," or " sooty partings.126 TIDESWELL AND WHEELER ON FUSAIN AND ITS OXIDATION. atmospheric temperature) of all the ingredients of the Hamstead coal. It would not however be justifiable to assume that fusains from other coals behave similarly-Winmill’s work indeed suggests that they do not-and further experiments with a number of samples of fusain and of the coals associated with them were therefore undertaken. During the progress of this work which was begun in 1919, determinations of the rates of oxidation of a number of fusains from different coal-fields have been published by Graham (Trans. Inst. Min. Eng. 1923 66 41) who has summarised his results as follows “ This ingredient of coal may vary very considerably in composition but such variaticn does not appear a t low temper-atures to affect materially the absorption of oxygen which in all cases is considerably smaller than that shown by a bituminous coal liable to spontaneous combustion.I n general from the chemical point of view fusain may be exonerated from being considered as the source of the main production of heat during the initial stages of most cases of spontaneous combustion.’, The following results may be quoted from Graham’s work the oxygen absorbed being expressed in C.C. a t N.T.P. per gram of fusain : Oxygen absorbed from air at Fusain description. 30” during 96 hours. C.C. Mossfield seam (North Staffs.) .................................1.93 ( a ) Soft variety ......... 1-19 f ( a ) Soft variety .................................... 1.87 l ( b ) Hard variety ................................. 1-61 Seven Foot seam (North Staffs.) { ( b ) Hard variety ......... 2.04 The absorption of oxygen by the actual coals with which the fusains were associated was not measured but Graham compared his results with some obta,ined by Winmill (ibid. 1916 51 493), under similar conditions of experiment for coals “ liable to spon-taneous combustion,’’ the values for which lay between 3.0 and 6.0 C.C. A closer scrutiny of Winmill’s figures shows however, that coal from.the same fields as those from which Graham’s fusains were obtained did not absorb oxygen any more readily an6Graham’s generalisation does not seem to us justifiable on the evidence.We have measured the absorption of oxygen of a number of coals and of the fusains actually associated with each and we cannot agree that fusains in general absorb oxygen a t slower rates than do coals liable to spontaneous combustion. Seventeen samples of fusain with samples of the adjoining coals, were collected for us by H.M. Inspectors of Mines and from these four were chosen according to their apparent purity for oxidation tests. The samples were as follows : STUDIES IN THE COMPOSITION OF COAL. 127 Lccb. No. A . From Top Mards Barnsley Seam Hucknall No. 2 Pit Notts. Lab. No. B. From Robin’s Seam Cannock Old Coppice Colliery, Walsall Staffs. Lab. No. C. F’rom Deep Softs Seam Mapperley Colliery Notts. Lab. No.D. From Dysart Main Colliery Fife. Analytical data respecting these samples are given in Table I. TABLE I. A. B. C. D. --- Fusain. Coal. Fusain. Coal. Fusain. Coal. Fusain. Coal. Moisture per cent. ... 5.6 9.4 5.6 8.9 2-6 9.8 5.7 10.9 matter (Other) 15.7 39.0 17.1 39.8 13.0 40.4 12.3 35.9 than moisture) ... Ash ..................... 10.3 3.3 14.7 8.3 12.5 7.7 11.8 1.3 Carbon per cent. (on Hydrogen ............ 3-0 5-0 3.3 4.8 3.0 4.7 3.2 4.6 Oxygen ............... 7-0 12.8 6-1 15-3 6.4 16.5 10.5 15.1 Nitrogen ............... 0.4 2.2 0.4 1.5 0.7 1.9 0.4 1.3 Sulphur ............... 0.2 0.9 10.4 4.9 2-4 1.3 1.3 0.5 FIG. 1. ash-free dry coal) )89*4 79.1 79.8 73.5 87.5 75.6 84.6 78.5 flME3 MOWRS. The mehhod of experiment was to circulate oxygen in a closed system through the coal or fusain packed in a tube maintained at a constant temperature.* The absorption of oxygen was calculated * Details of the apparatus used and of the method of experiment are given in J.1920 117 795 whilst a diagram of a simi1a.r apparatus is shown in J. 1912 101 831 128 TIDESWELL AND WHEELER ON FUSAIN AND ITS OXIDATION. from the reduction of pressure. Before and after oxidation at a given temperature each sample was heated in a vacuum at 200". The results obtained are shown diagrammatically in Figs. 1 and 2 and are summarised in Tables I1 and 111. These results cannot be directly compared with those of Graham, for he used air in his experiments but Winmill has found (Trans. Inst. Bin. Eng. 1916 51 493) that the absorption of oxygen by coal is nearly proportional to the square root of its concentration, FIG 2.TABLE 11. substance. Oxygen absorbed. C.C. at N.T.P. per gram of ash-free dry Sample. A. B. C. Temp. (hours). Fusam. Coal. Fusain. Coal. Fusam. Coal. 1.3 1-0 1.4 1.2 1.8 1.5 2.3 2.4 2.5 2.6 3-2 3.8 300 3-5 4.3 4.0 5.0 5.1 6.4 196 4.3 5.8 4.8 6-6 6.2 8.1 10.5 19-2 12.2 22.4 11.0 25.0 '*'" { k! 22.0 48.0 24.0 47.0 22.8 61.0 Time & 0 D. Fusain. Coal. 0.8 1.4 1.8 3.8 2.9 6.7 3.5 8.5 7.2 23.8 17.0 59.0 7 STUDIES IN THE COXPOSITION O F COAL. 129 TAELE 111. Ratio Oxygen absorbed by fusniih Osygeil ubsorbed by coul. Temp. (hours). *A. B. C. D. Time Sample. 1.3 1.2 1.2 0.6 0.95 0.96 0-84 0.47 30" !;k 0.83 0.81 0.80 0.43 0.74 0.73 0.76 0 4 1 0.55 0.55 0.44 0.30 0.46 0.48 0.38 0.25 \ 96 100" 150 10 so that a rough comparison can be made if Graham's figures are doubled.It then appears that the fusains he used were decidedly less readily oxidised a t 30" than most of those we have investigated. We suggest that this is due in part t o the different experimental methods used (Graham for example does not appear to have allowed for the oxidation of his samples a t atmospheric temperature previous to their introduction into his apparatus) but mainly to differences in the nature of the fusains themselves. The abnormally low rate of oxidat'ion of the Barnsley fusain recorded by Winmill would appear to be due to weathering of the sample previous to his tests. It will be seen froin Tables 11 and I11 that with three of the pairs of samples examined the initial absorption of oxygen by the fusain a t 30" was greater than that by the coal but on comparing the results obtained a t 30" and loo" the oxidisabilit'y of fusain is found to increase less rapidly with temperature than bhat of the coal.The temperature coefficients of the amounts of oxygen absorbed during the early stages (up io 10 hours) are : A. B. C. D. Hamstead. Fusain ...... 1.24 1-27 1-12 1.29 1.20 Coal ......... 1.34 1.34 1.39 1.37 1-35 In each instance the coefficient is less than 2 and probably is the resultant of two coefficients. The reaction between oxygen and coal is not simple it may be expressed as follows : Coal and oxygen + coal-oxygen (adsorbed) + coal-oxygen (com-plex) + oxidised coal + oxides of carbon + water.The last phase of the reaction is incomplete at low temperatures, but can be completed by raising t'he temperature (it is nearly complete a t 200") ; a t such low temperatures absorption of oxygen is determined by the formation of the coal-oxygen complex. Com-pared with the rate of formation of this complex the first action of adsorption may be regarded as instantaneous. The rate of complex Iormaiion will therefore depend on the concentration of oxygen on the surface of the coal. The temperature coefficient of the con-VOL. CXXVII. 130 TIDESWELL AND WHEELER ON FUSAIN AND ITS OXIDATION. centration of adsorbed oxygen on the surface of the coal is less than unity and is probably about 0.80 (see Graham Trans. Inst. M i n . Eng.1916 52 338; Tideswell and Wheeler J. 1919 115 895). Assuming that the rate a t which the coal-oxygen complex is formed is directly proportional to the concentration of the oxygen main-tained on the surface of the coal and that its temperature coefficient is 2 the expected coefficient for the series of reactioiis would be 1.6. An explanation of this is that the surface of the coal becomes clogged by the products of decom-position of the complex an effect which would be greater the higher the temperature of reaction and more noticeable with fusain than with coal because of the more open texture of its surface. A study of the gases evolved during the oxidations (see Table IV) suggests that the mode of oxidation of fusain and of coal is similar. At 30" the amount of carbon monoxide was too small to admit of exact determination but a t 100" the volumes were both larger and more regular in amount and it was found that the ratio between the carbon dioxide and carbon monoxide produced at this tem-perature lay within the same range (2.4 to 3-4) with the fusains as with the coals.TABLE IV. The observed values are less. Oxides of carbon evolved. Per cent. of oxygen absorbed. Sample. Temp. A. B. C. D. 4.0 0.8 1.6 0-8 1.5 3.2 6.6 0.7 30" Carbon dioxide { g::rh 100 Carbon dioxide (Ezp 12.8 11.7 10.8 14.5 10.6 12.1 14.5 . 17.6 4.0 4.0 4.4 6.2 6-2 100 Carbon monoxide { gzp 4*7 4.0 4-9 {El?? 2.7 2.9 2.7 3.3 Ratio 2 2-65 2.5 2.4 3.4 With none of the fusains examined was the rate of absorption of oxygen a t low temperatures so rapid as with the Hamstead fusain, which may be regarded as exceptional.Fusain does not form an important part by weight (rarely more than 5%) of the mass of a coal but it occurs frequently in patches or in layers of considerable extent generally adjacent to or embedded in bright coal and its porous nature allows of ready access of oxygen. Both its chemical properties and its physical state therefore enable it to produce the first local rise in temperature that may result in self-heating of the adjacent coal. Once the temperature has risen the continuance of the heating is no doubt mainly due to oxidation of the coal. It is not to be expected that all fusains no matter from what seams of coal they are procured should have similar chemical and physical properties any more than that all coals should be similar STUDIES IN THE COMPOSITION OF COAL.131 We have in fact evidence from the work of Sinnatt (Trans. Inst. Min. Eng. 1921 62 156) that in the Lancashire coal-fields there are a t least two types a dense and a pulverulent variety whilst, as already mentioned the Hamstead fusain with which we made our previous experiments seems to be of a particularly reactive character. We concluded from our work on banded bituminous coal (Zoc. cit. p. 634) that the three principal ingredients of Hamstead coal vitrain clarain and durain are each composed of a " reactive " group of compounds together with a relatively " inert " material, and differ from one another mainly in the proportions of these constituents contained in them.Although the fact was not empha-sised a t the time the chemical examinatiun of the Hamstead fusain showed that it also must be regarded as containing a certain pro-portion of " reactive " constituents of similar type to those in the coal which is responsible for many of its properties. Similarly it would appear from Sinnatt's work and from our own observations that many if not all fusains consist of an intimate mixture of coaly material with an " inert," or true fusain constituent. The occurrence of fusaiii in coal seams is usually attributed to rapid aerial decay of the plants at or near the water surface of the swamps in which most of the dibris was submerged and the process most often appears to have taken effect on the woody parts of the plants.There is no reason why such aerial decomposition should always have been completed before the plants became submerged and anaerobic decomposition began; indeed it is more probable that in the majority of instances the aerial decay was not complete. Fusains may therefore be expected to differ from one another not only occasionally by reason of differences in the plant remains fusainised but also frequently because the material has suffered in differing degree an in part aerobic and in part anaerobic decom-position the latter resulting in ulmification. Lomax has indeed, observed complete stems of plants that have been fusainised on the outside and consist of true coal within (Trans. Inst. Nin. Eng., 1921 62 171) but we suggest that each individual fusain fibre may often consist of an inner core of coaly material with an outer layer of true fusain with no doubt intermediate zones merging the one into the other ; and there may also be only partial fusainis-ation of some of the cell-walls composing the fibre.The " true fusain " material appears to be quite insoluble in organic solvents; it yields mainly oxides of carbon and methane on distillation with little or no liquid products and consists usually of thickened and " carbonised " cell-walls. We consider that the intimate admixture of different proportions of oxidisable coaly material with this chemically " inert " but very porous true fusain F 132 POIV'VELL AND WHITTAKER THE CHEMISTRY OF LIGNIN. material mainly determines the different degrees of oxidisability of fusains as they exist in coal the fusain in the Hamstead coal for example containing a high proportion of coaly material throughout its fibres Support is lent to this view by analyses of a number of fusains made for us by Mr.A. E. Beet. These samples of fusain had been collected with great care and before they were subjected to analysis were examined closely for fragments of adhering coal. Yet it was found that each could be separated into two distinct classes of material by sieving through a 40's mesh. The fraction which remained on the sieve was associated with much coaly material to judge by the results of analysis (more particularly distillation tests at 900") though it could not be recognised as coal; whilst that which passed through was on the same evidence, mainly what we have termed " true fusain " material.DEPARTNENT OF FUEL TECHNOLOGY, SREFFIELD UNIVERSITY. [Received October llth 1924. TIDESWELL AND WHEELER ON FUSAIN AND ITS OXIDATION. 125 XX1.-On Fusain artd its Oxidation. Studies in the Cornpo&ion of Coal. By FREDERICK VINCENT TIDESWELL and RICIFARD VERNON WHEELER. SPONTANEOUS combustion in a seam of coal in so far as it may be determined by the chemical composition of the materials composing the seam originates with the most readily oxidisable ingredient thereof. Amongst mining men there is a belief the history of which it is unnecessary to trace that a frequent cause of spon-taneous combustion is the presence in the seam of fusain; * that fire actually originates in bands of fusain when such are present, and travels preferentially along them.Data regarding the rate of oxidation of a fusain have been supplied by Winmill (Trans. Inst. Min. Eng. 1913 46 563) who concluded that of all parts of the Barnsley seam which he examined in detail the fusain was the least capable of heating spontaneously. Our own experiments when using coal from the Hamstead Thick seam (J. 1920 117 794) gave quite different results. The vitrain, clarain and durain (the brilliant bright and dull portions of the seam) absorbed oxygen a t rates graded in the direction expected from previous work on the chemical constitution of these ingredients of banded bituminous coal (J. 1919 115 619) but the fusain stood apart. At 15" and 50" its absorptive power for oxygen was several times greater than that of the rest of the coal although at 100" it was of the same order.From this it can be concluded that the fuaain weight fcr weight is the most liable to self-heat (from * Sometimes called " mother of coal," " mineral charcoal," " dant," or " sooty partings. 126 TIDESWELL AND WHEELER ON FUSAIN AND ITS OXIDATION. atmospheric temperature) of all the ingredients of the Hamstead coal. It would not however be justifiable to assume that fusains from other coals behave similarly-Winmill’s work indeed suggests that they do not-and further experiments with a number of samples of fusain and of the coals associated with them were therefore undertaken. During the progress of this work which was begun in 1919, determinations of the rates of oxidation of a number of fusains from different coal-fields have been published by Graham (Trans.Inst. Min. Eng. 1923 66 41) who has summarised his results as follows “ This ingredient of coal may vary very considerably in composition but such variaticn does not appear a t low temper-atures to affect materially the absorption of oxygen which in all cases is considerably smaller than that shown by a bituminous coal liable to spontaneous combustion. I n general from the chemical point of view fusain may be exonerated from being considered as the source of the main production of heat during the initial stages of most cases of spontaneous combustion.’, The following results may be quoted from Graham’s work the oxygen absorbed being expressed in C.C. a t N.T.P.per gram of fusain : Oxygen absorbed from air at Fusain description. 30” during 96 hours. C.C. Mossfield seam (North Staffs.) ................................. 1.93 ( a ) Soft variety ......... 1-19 f ( a ) Soft variety .................................... 1.87 l ( b ) Hard variety ................................. 1-61 Seven Foot seam (North Staffs.) { ( b ) Hard variety ......... 2.04 The absorption of oxygen by the actual coals with which the fusains were associated was not measured but Graham compared his results with some obta,ined by Winmill (ibid. 1916 51 493), under similar conditions of experiment for coals “ liable to spon-taneous combustion,’’ the values for which lay between 3.0 and 6.0 C.C. A closer scrutiny of Winmill’s figures shows however, that coal from.the same fields as those from which Graham’s fusains were obtained did not absorb oxygen any more readily an6Graham’s generalisation does not seem to us justifiable on the evidence.We have measured the absorption of oxygen of a number of coals and of the fusains actually associated with each and we cannot agree that fusains in general absorb oxygen a t slower rates than do coals liable to spontaneous combustion. Seventeen samples of fusain with samples of the adjoining coals, were collected for us by H.M. Inspectors of Mines and from these four were chosen according to their apparent purity for oxidation tests. The samples were as follows : STUDIES IN THE COMPOSITION OF COAL. 127 Lccb. No. A . From Top Mards Barnsley Seam Hucknall No.2 Pit Notts. Lab. No. B. From Robin’s Seam Cannock Old Coppice Colliery, Walsall Staffs. Lab. No. C. F’rom Deep Softs Seam Mapperley Colliery Notts. Lab. No. D. From Dysart Main Colliery Fife. Analytical data respecting these samples are given in Table I. TABLE I. A. B. C. D. --- Fusain. Coal. Fusain. Coal. Fusain. Coal. Fusain. Coal. Moisture per cent. ... 5.6 9.4 5.6 8.9 2-6 9.8 5.7 10.9 matter (Other) 15.7 39.0 17.1 39.8 13.0 40.4 12.3 35.9 than moisture) ... Ash ..................... 10.3 3.3 14.7 8.3 12.5 7.7 11.8 1.3 Carbon per cent. (on Hydrogen ............ 3-0 5-0 3.3 4.8 3.0 4.7 3.2 4.6 Oxygen ............... 7-0 12.8 6-1 15-3 6.4 16.5 10.5 15.1 Nitrogen ............... 0.4 2.2 0.4 1.5 0.7 1.9 0.4 1.3 Sulphur ............... 0.2 0.9 10.4 4.9 2-4 1.3 1.3 0.5 FIG.1. ash-free dry coal) )89*4 79.1 79.8 73.5 87.5 75.6 84.6 78.5 flME3 MOWRS. The mehhod of experiment was to circulate oxygen in a closed system through the coal or fusain packed in a tube maintained at a constant temperature.* The absorption of oxygen was calculated * Details of the apparatus used and of the method of experiment are given in J. 1920 117 795 whilst a diagram of a simi1a.r apparatus is shown in J. 1912 101 831 128 TIDESWELL AND WHEELER ON FUSAIN AND ITS OXIDATION. from the reduction of pressure. Before and after oxidation at a given temperature each sample was heated in a vacuum at 200". The results obtained are shown diagrammatically in Figs. 1 and 2 and are summarised in Tables I1 and 111. These results cannot be directly compared with those of Graham, for he used air in his experiments but Winmill has found (Trans.Inst. Bin. Eng. 1916 51 493) that the absorption of oxygen by coal is nearly proportional to the square root of its concentration, FIG 2. TABLE 11. substance. Oxygen absorbed. C.C. at N.T.P. per gram of ash-free dry Sample. A. B. C. Temp. (hours). Fusam. Coal. Fusain. Coal. Fusam. Coal. 1.3 1-0 1.4 1.2 1.8 1.5 2.3 2.4 2.5 2.6 3-2 3.8 300 3-5 4.3 4.0 5.0 5.1 6.4 196 4.3 5.8 4.8 6-6 6.2 8.1 10.5 19-2 12.2 22.4 11.0 25.0 '*'" { k! 22.0 48.0 24.0 47.0 22.8 61.0 Time & 0 D. Fusain. Coal. 0.8 1.4 1.8 3.8 2.9 6.7 3.5 8.5 7.2 23.8 17.0 59.0 7 STUDIES IN THE COXPOSITION O F COAL. 129 TAELE 111. Ratio Oxygen absorbed by fusniih Osygeil ubsorbed by coul.Temp. (hours). *A. B. C. D. Time Sample. 1.3 1.2 1.2 0.6 0.95 0.96 0-84 0.47 30" !;k 0.83 0.81 0.80 0.43 0.74 0.73 0.76 0 4 1 0.55 0.55 0.44 0.30 0.46 0.48 0.38 0.25 \ 96 100" 150 10 so that a rough comparison can be made if Graham's figures are doubled. It then appears that the fusains he used were decidedly less readily oxidised a t 30" than most of those we have investigated. We suggest that this is due in part t o the different experimental methods used (Graham for example does not appear to have allowed for the oxidation of his samples a t atmospheric temperature previous to their introduction into his apparatus) but mainly to differences in the nature of the fusains themselves. The abnormally low rate of oxidat'ion of the Barnsley fusain recorded by Winmill would appear to be due to weathering of the sample previous to his tests.It will be seen froin Tables 11 and I11 that with three of the pairs of samples examined the initial absorption of oxygen by the fusain a t 30" was greater than that by the coal but on comparing the results obtained a t 30" and loo" the oxidisabilit'y of fusain is found to increase less rapidly with temperature than bhat of the coal. The temperature coefficients of the amounts of oxygen absorbed during the early stages (up io 10 hours) are : A. B. C. D. Hamstead. Fusain ...... 1.24 1-27 1-12 1.29 1.20 Coal ......... 1.34 1.34 1.39 1.37 1-35 In each instance the coefficient is less than 2 and probably is the resultant of two coefficients.The reaction between oxygen and coal is not simple it may be expressed as follows : Coal and oxygen + coal-oxygen (adsorbed) + coal-oxygen (com-plex) + oxidised coal + oxides of carbon + water. The last phase of the reaction is incomplete at low temperatures, but can be completed by raising t'he temperature (it is nearly complete a t 200") ; a t such low temperatures absorption of oxygen is determined by the formation of the coal-oxygen complex. Com-pared with the rate of formation of this complex the first action of adsorption may be regarded as instantaneous. The rate of complex Iormaiion will therefore depend on the concentration of oxygen on the surface of the coal. The temperature coefficient of the con-VOL. CXXVII. 130 TIDESWELL AND WHEELER ON FUSAIN AND ITS OXIDATION.centration of adsorbed oxygen on the surface of the coal is less than unity and is probably about 0.80 (see Graham Trans. Inst. M i n . Eng. 1916 52 338; Tideswell and Wheeler J. 1919 115 895). Assuming that the rate a t which the coal-oxygen complex is formed is directly proportional to the concentration of the oxygen main-tained on the surface of the coal and that its temperature coefficient is 2 the expected coefficient for the series of reactioiis would be 1.6. An explanation of this is that the surface of the coal becomes clogged by the products of decom-position of the complex an effect which would be greater the higher the temperature of reaction and more noticeable with fusain than with coal because of the more open texture of its surface.A study of the gases evolved during the oxidations (see Table IV) suggests that the mode of oxidation of fusain and of coal is similar. At 30" the amount of carbon monoxide was too small to admit of exact determination but a t 100" the volumes were both larger and more regular in amount and it was found that the ratio between the carbon dioxide and carbon monoxide produced at this tem-perature lay within the same range (2.4 to 3-4) with the fusains as with the coals. TABLE IV. The observed values are less. Oxides of carbon evolved. Per cent. of oxygen absorbed. Sample. Temp. A. B. C. D. 4.0 0.8 1.6 0-8 1.5 3.2 6.6 0.7 30" Carbon dioxide { g::rh 100 Carbon dioxide (Ezp 12.8 11.7 10.8 14.5 10.6 12.1 14.5 . 17.6 4.0 4.0 4.4 6.2 6-2 100 Carbon monoxide { gzp 4*7 4.0 4-9 {El?? 2.7 2.9 2.7 3.3 Ratio 2 2-65 2.5 2.4 3.4 With none of the fusains examined was the rate of absorption of oxygen a t low temperatures so rapid as with the Hamstead fusain, which may be regarded as exceptional.Fusain does not form an important part by weight (rarely more than 5%) of the mass of a coal but it occurs frequently in patches or in layers of considerable extent generally adjacent to or embedded in bright coal and its porous nature allows of ready access of oxygen. Both its chemical properties and its physical state therefore enable it to produce the first local rise in temperature that may result in self-heating of the adjacent coal. Once the temperature has risen the continuance of the heating is no doubt mainly due to oxidation of the coal.It is not to be expected that all fusains no matter from what seams of coal they are procured should have similar chemical and physical properties any more than that all coals should be similar STUDIES IN THE COMPOSITION OF COAL. 131 We have in fact evidence from the work of Sinnatt (Trans. Inst. Min. Eng. 1921 62 156) that in the Lancashire coal-fields there are a t least two types a dense and a pulverulent variety whilst, as already mentioned the Hamstead fusain with which we made our previous experiments seems to be of a particularly reactive character. We concluded from our work on banded bituminous coal (Zoc. cit. p. 634) that the three principal ingredients of Hamstead coal vitrain clarain and durain are each composed of a " reactive " group of compounds together with a relatively " inert " material, and differ from one another mainly in the proportions of these constituents contained in them.Although the fact was not empha-sised a t the time the chemical examinatiun of the Hamstead fusain showed that it also must be regarded as containing a certain pro-portion of " reactive " constituents of similar type to those in the coal which is responsible for many of its properties. Similarly it would appear from Sinnatt's work and from our own observations that many if not all fusains consist of an intimate mixture of coaly material with an " inert," or true fusain constituent. The occurrence of fusaiii in coal seams is usually attributed to rapid aerial decay of the plants at or near the water surface of the swamps in which most of the dibris was submerged and the process most often appears to have taken effect on the woody parts of the plants.There is no reason why such aerial decomposition should always have been completed before the plants became submerged and anaerobic decomposition began; indeed it is more probable that in the majority of instances the aerial decay was not complete. Fusains may therefore be expected to differ from one another not only occasionally by reason of differences in the plant remains fusainised but also frequently because the material has suffered in differing degree an in part aerobic and in part anaerobic decom-position the latter resulting in ulmification. Lomax has indeed, observed complete stems of plants that have been fusainised on the outside and consist of true coal within (Trans.Inst. Nin. Eng., 1921 62 171) but we suggest that each individual fusain fibre may often consist of an inner core of coaly material with an outer layer of true fusain with no doubt intermediate zones merging the one into the other ; and there may also be only partial fusainis-ation of some of the cell-walls composing the fibre. The " true fusain " material appears to be quite insoluble in organic solvents; it yields mainly oxides of carbon and methane on distillation with little or no liquid products and consists usually of thickened and " carbonised " cell-walls. We consider that the intimate admixture of different proportions of oxidisable coaly material with this chemically " inert " but very porous true fusain F 132 POIV'VELL AND WHITTAKER THE CHEMISTRY OF LIGNIN. material mainly determines the different degrees of oxidisability of fusains as they exist in coal the fusain in the Hamstead coal for example containing a high proportion of coaly material throughout its fibres Support is lent to this view by analyses of a number of fusains made for us by Mr. A. E. Beet. These samples of fusain had been collected with great care and before they were subjected to analysis were examined closely for fragments of adhering coal. Yet it was found that each could be separated into two distinct classes of material by sieving through a 40's mesh. The fraction which remained on the sieve was associated with much coaly material to judge by the results of analysis (more particularly distillation tests at 900") though it could not be recognised as coal; whilst that which passed through was on the same evidence, mainly what we have termed " true fusain " material. DEPARTNENT OF FUEL TECHNOLOGY, SREFFIELD UNIVERSITY. [Received October llth 1924.

ISSN:0368-1645    

DOI:10.1039/CT9252700125

出版商:RSC    

年代:1925

数据来源: RSC

摘要:

132 POIV'VELL AND WHITTAKER THE CHEMISTRY OF LIGNIN. XXI1.-The Chemistry of Lignin. Part I I . A Comparison of Lignins Derived from Various Woods. By WALTER JAMES POWELL and HENRY WHITTAKER. IN Part I of this series (J. 1924 125 357) the preparation and properties of lignin derived from flax shoves and of several of its derivatives were described. The chief conclusions drawn were that the empirical formula for flax lignin which agrees most closely with all the analytical data is C,5H,,0,, and that the molecule contains one active aldehyde group and nine hydroxyl groups, of which four are methylated. The investigation has now been extended on the same lines to lignins obtained from a number of woods and poplar birch ash spruce larch and pine lignins, together with some derivatives of these substances have been examined.The wood lignins were isolated in the same way as flax lignin t'he wood in the form of small chips being digested for 6 to 10 hours under pressure at temperatures varying from 140" to 160" with caustic soda solution the strength of which varied from 8 to 12%. The black liquor was drained from the cellulose and treated while still hot with a slight excess of hydrochloric acid, the precipitated lignin being washed by decantation with hot dilute hydrochloric acid centrifuged and dried. An objection might be raised that tlhis method of isolation would cause internal changes to take place in the lignin molecule. Lignosulphonic acid however PART Ir. A COMPARISON OF LIGNINS ETC. 133 has been obtained from spruce wood by EorBe and Hall ( J .SOC. Chem. Ind. 1924 43 2 5 7 ~ ) by a mild process-the action of a 7% solution of sulphurous acid at 100-1 lO"-and the composition of this substance corresponds with the formula C26H30012S from which the formula C,,H,,O for lignin is obtained. This requires C = 64.4 H = 5.9% ; and these figures are in close agreement with our results (Table I). Our product is therefore not more highly condensed than that of Dorde and Hall and both are probably closely related to lignin as i t exists in the lignocellulose complex. The crude lignin was purified by pouring the solution in aqueous acetone into a large volume of hot 20% hydrochloric acid the precipitate being collected and thoroughly washed with hot water. The results now obtained show conclusively that the lignins from the different natural sources so far examined are derivatives of the same hydroxy-compound and that they differ only in the number of methoxyl groups which they contain.This difference is mainly due to the fact that the methoxyl content of lignin in wood varies from one species to another while in any one species variations occur according to the age of the tree. I n addition the methoxyl content of lignin isolated in the manner already described is affected by the strength of caustic soda solution and the time and tem-perature of digestion. Lignin as isolated is therefore a mixture of methylated derivatives of a polyhydroxy-compound and i t should be possible by chemical means to effect separation into iractions of definite methoxyl content but our attempts to do so have not yet met with success.The separate fractions obtained by precipitating lignin from its solution in caustic soda by addition of hydrochloric acid gave the same figures on analysis. I n deducing the formula c4,H480,6 from the analytical results given by flax lignin and its derivatives the assumption was made that the molecule contained a definite number of methoxyl groups, vhereas in our present view there is no reason to suppose that such is the case. Instead of the total of nine hydroxyl groups indicated 11y analysis of acetyl-lignin i t is possible to suggest forrnulx! con-taining eight or ten hydroxyl groups (e.g. C,,H,,O1,) which agree equally well with the analytical data. At this stage of the work, however i t is not desirable to make a decision in favour of one or the other of these formula and until more data are available we intend to continue using the formula adopted for flax lignin, From the six wood lignins purified as described above the acetyl compounds were prepared by treatment on the steam-bath with acetic anhydride and sulphuric acid.The acetyl content varied according to the methoxyl content but in each case using the '4 5"48O 16 134 POWELL AND WHITTAKER THE CHEMISTRY OF LIGNIN. empirical formula C45H48016 as the basis of calculation the total of acetylated and methylated hydroxyl groups was nine although the actual number of methylated groups varied between three and five. All the acetyl compounds were insoluble in cold alkali and i t is therefore unlikely that there are any carboxyl groups in the molecule.The variations in methoxyl content of the various wood lignins prepared were not sufficient to affect the determinations of carbon and hydrogen which were carried out on the purified samples and the figures obtained were constant within the limits of experimental error. Table I gives a summary of the analytical results and also the number of groups calculated on the basis of the formula C4,H,,0, for the parent hydroxyl compound itself. It is proposed to assign the name ZignoZ to this compound. Substance Determin-analysed. ation. Lignin. C H CHO Acetyl-lignin. OMe COCH, No. of OMe groups. No. of COaCH groups. Total groups. Acetylmethyl- OMe No. of OMe groups. No. of COCH groups.Total groups. lignin COCH, TABLE I. Source of Lignin. r h -. Flax. Larch. Pine. Spruce. Ash. Birch. Poplar. 63.9 63.8 63.4 64.0 63.2 63.2 63.3 5.8 5.2 5.6 5.5 5-6 5.5 5-8 11.8 9.0 11-5 11.0 13.3 15.2 12.6 20.6 23.0 18.9 19.4 17-6 14.5 17.5 4.0 3.1 3.9 3-8 4.5 5.0 4.3 5.0 6-8 4.5 4.8 4.3 3.4 4.3 9.0 8.9 8.4 8.6 8.8 8.4 8.6 20-3 19.9 20.4 23.1 20.0 22.4 22.7 11.1 11.8 10.5 8.0 11.3 8.1 7.5 6.5 6.4 6.5 7.2 6.4 7.0 7.0 2.6 2.7 2.4 1.8 2.6 1.8 1.7 9.1 9-1 8.9 9.0 9.0 8.8 8.7 3.1 - 2.9 3.1 - 3.2 -The table shows that lignol from each of the wood lignins examined has the same empirical formula and the same number of hydroxyl groups as that from flax lignin. In order to verify this statement experimentally attempts have been made to isolate lignol from the various lignins by the action of hydriodic acid.However on treating lignin with hydriodic acid (d 1.7) at 130° a dark brown product which appeared to be a mixture was obtained. The main fraction of this product wm insoluble in caustic soda and cannot therefore be lignol and as the percentage of carbon found is much higher than that calculated i t appears that reduction takes place during the reaction with hydriodic acid. Confirmation of the results and conclusions drawn from the analysis of the acetylated lignins was obtained by examination of the methylated derivatives. The latter were prepared by treatment of the sodium hydroxide solution of lignin with methyl sulphate in the cold. It is not possible to methylate more than seven of the hydroxyl groups under the conditions employed an PART 11.A COMPARISOX OF LIGNINS ETC. 133 in some cases full methylation was obtained only after several treatments. The product from a single treatment however after being washed with dilute sodium hydroxide solution was acetylated in the usual manner and the total of methoxyl and acetyl groups in all the products was found t o be practically constant. It was stated in the paper on flax lignin (Zoc. cit.) that the proportion of acetyl in acetj-lmethyl-lignin was too low to account for the presence of two acetyl groups. In the experiments on vhich this statement was based acetic anhydride alone was used as the acetylating agent, but i t has since been found that in presence of sulphuric acid the diacetyl derivative is readily formed.The analytical data given in Table I for the acetylmethyl-lignins strongly support the view that all the various lignins examined have the same empirical composition and number of hydroxyl groups in the molecule. Derivatives of an entirely different character from those already described result when lignin is treated with chlorine or bromine, and if there were any fundamental differences in the molecular structure of the various lignins i t is unlikely that the same halogen-ated derivative would be obtained in each case. In our study of flax lignin we found that the chlorination or bromination product contained twelve halogen atoms and that a large quantity of hydrogen chloride or bromide was evolved during halogenation. Most of the methoxyl groups originally present in the lignin were removed chlorolignin apparently containing two and bromolignin containing only one methoxyl group.Six of the twelve chlorine atoms in flax chlorolignin were eliminated with great ease for example by clissolving the fully chlorinated derivative in cold dilute sodium hydroxide the hexachlorolignin being precipitated on acidification. Hexachlorolignin contains only one methoxyl group and therefore the fully chlorinated product dodecachloro-lignin can contain only one such group and is similar to the brorno-compound in that respect. The higher figure €or methoxyl obtained on analysis is due t o the ease with which hydrogen chloride is eliminated during estimation in the Zeisel apparatus. The Perkiii method for the determination of acetyl also gives high results in the case of acetyldodecachloroligi~in owing to the liberation of ethyl chloride.The six u-ood lignins have been brominated and subsequently acetylated . The dodecabromolignins and their acetyl derivatives 011 analysis gave results agreeing closely with those obtained from the corresponding products derived from flax lignin (Table 11). The dodecachlorolignins prepared from two wood lignins were similar in composition to flax dodecachlorolignin. A mixturc o 136 POWELL AND WHITTAKER THE CHEMISTRY OF LIGNIN. the six wood dodecachlorolignins on solution in dilute sodium hydroxide solution and reprecipitation with hydrochloric acid, gave a product comparable in all respects with flax hexachlorolignin.It may also be noted that the various acetylated dodecachlorolignins were more readily hydrolysed than the corresponding bromo-compounds a behaviour similar to that of the derivatives from flax lignin and that in all cases both acetyl derivatives were insoluble in cold sodium hydroxide solution. A third type of derivative nitrolignin has been prepared from each wood lignin and the products were identical with that from flax lignin in composition three nitro-groups having been introduced into the molecule. As in the case of flax nitrolignin a part of the nitrogen is present as organic nitrate as is evident by the fact that a proportion can be estimated by the Lunge or Schultze-Tremann method. The total nitrogen however can only be determined by the Dumas or Kjeldahl method.The nitration of lignin proceeds equally readily whether nitric acid alone (40%) or a mixture of nitric and sulphuric acids is used the products containing the same percentage of nitrogen. These facts indicate the prob-ability of the presence of aromatic nuclei in lignin. Acetylnitrolignin is soluble in cold alkalis and it is possible that nitrolignin conta,ins one or more carboxyl groups. In this connexion it may be noted that elementary analysis of the nitro-compounds shows that some oxidation has taken place in addition to nitration. Owing to the ready hydrolysis of the acetylnitrolignins it is difficult to deduce the number of hydroxyl groups in the molecule from analyses of this compound. TABLE 11. Substance analysed. Dodecabromo-lignin Acetyldodeca-bromolignin Dodecachloro-lignin Ni trolignin Hexachloro -lignin Methyl-lignin-phenylhydrazone N - 7.5* * Samples prepared from a mixture of equal quantities of the wood lignins.Source of Lignin. Detemin- -. -~ -..- ~ _ _ ation. Flax. Larch. Pine. Spruce. Ash Birch. Poplar. 28.0 28.2 - - 28.1 - -1.5 1.6 - - 1.6 - -55.2 55.0 54.8 55.2 55.1 54.7 54-9 1.8 1.6 - - - 2.4 2.1 /OMe \CO-CH 9.4 9.8 9.0 9.8 - - 9.2 {E c1 35.1 35.5 - - - 36.0 -{OMe 5.2 4.9 - - - 5.1 -50.4 50.2 - 50.6 3.8 3.8 - 3.9 4.2 4.1 4.1 - 4.3 - 4.2 3.0 3.2 2.6 3.1 3.0 3.3 -(: 50.1 49.5* 3.0 3*2* 3-45 3*5* 20.8 204* 1 :M PART 11. A COMPARISON OF LIQNINS ETC. 137 Some discussion has recently taken place in the literature as to whether or not lignin evolves furfuraldehyde on distillatmion with 12% hydrochloric acid and in view of this we have carefully examined our products using the volumetric method for the estim-ation of pentosans in wood cellulose previously described by us ( J .SOC. Chem. Ind. 1924 43 35T). Average results for the six crude lignins obtained by acidification of the alkaline liquor showed the presence of 0.9% of pentosans. This value was reduced to 0.3% by one purification from acetone and hydrochloric acid whilst, the product from a second purification gave no trace of furfur-aldehyde. We therefore regard as untenable the view of Hagglund (Cellulosechemie 1923 4 73) that lignin contains 5% of furfural-yielding carbohydrate as an integral part of the molecule. Of the sixteen oxygen atoms present in the molecule of lignin, nine are in the form of hydroxyl groups and one as an aldehyde group.The presence of the latter was indicated by measurements of the amount of Fehling’s solution reduced by lignin and was confirmed in the case of flax lignin by a volumetric determination of the amount of phenylhydrazine required to form the phenyl-hydrazone. The following experiment shows however that the monohydrazone is only formed under the mild conditions used in the volumetric method and that the rgaction can be made to proceed further. Methyl-lignin was allowed to react with a hot alcoholic solution of phenylhydrazine and the product freed from phenylhydrazine by several precipitations from acetone and hydro-chloric acid. Analysis showed that three phenylhydrazine molecules had reacted with each molecule of lignin and therefore that two ketonic groups must also be present.Methyl-lignin was used instead of lignin in order to avoid the formation of a phenyl-hydrazine ester. These results may be summarised by writing the formula for ljgnol in the extended form C,,H,,O,(CO),(CHO)(OH),. The details of. the experimental work are similar to those given in Part I for flax lignin and are therefore not repeated. The results are published by permission of the Director of Artillery, RESEARCH DEPARTMENT, to whom our thanks are due. ROYAL ARSENAL WOOLWICN. [Received October 21st 1924. 132 POIV'VELL AND WHITTAKER THE CHEMISTRY OF LIGNIN. XXI1.-The Chemistry of Lignin. Part I I . A Comparison of Lignins Derived from Various Woods.By WALTER JAMES POWELL and HENRY WHITTAKER. IN Part I of this series (J. 1924 125 357) the preparation and properties of lignin derived from flax shoves and of several of its derivatives were described. The chief conclusions drawn were that the empirical formula for flax lignin which agrees most closely with all the analytical data is C,5H,,0,, and that the molecule contains one active aldehyde group and nine hydroxyl groups, of which four are methylated. The investigation has now been extended on the same lines to lignins obtained from a number of woods and poplar birch ash spruce larch and pine lignins, together with some derivatives of these substances have been examined. The wood lignins were isolated in the same way as flax lignin t'he wood in the form of small chips being digested for 6 to 10 hours under pressure at temperatures varying from 140" to 160" with caustic soda solution the strength of which varied from 8 to 12%.The black liquor was drained from the cellulose and treated while still hot with a slight excess of hydrochloric acid, the precipitated lignin being washed by decantation with hot dilute hydrochloric acid centrifuged and dried. An objection might be raised that tlhis method of isolation would cause internal changes to take place in the lignin molecule. Lignosulphonic acid however PART Ir. A COMPARISON OF LIGNINS ETC. 133 has been obtained from spruce wood by EorBe and Hall ( J . SOC. Chem. Ind. 1924 43 2 5 7 ~ ) by a mild process-the action of a 7% solution of sulphurous acid at 100-1 lO"-and the composition of this substance corresponds with the formula C26H30012S from which the formula C,,H,,O for lignin is obtained.This requires C = 64.4 H = 5.9% ; and these figures are in close agreement with our results (Table I). Our product is therefore not more highly condensed than that of Dorde and Hall and both are probably closely related to lignin as i t exists in the lignocellulose complex. The crude lignin was purified by pouring the solution in aqueous acetone into a large volume of hot 20% hydrochloric acid the precipitate being collected and thoroughly washed with hot water. The results now obtained show conclusively that the lignins from the different natural sources so far examined are derivatives of the same hydroxy-compound and that they differ only in the number of methoxyl groups which they contain.This difference is mainly due to the fact that the methoxyl content of lignin in wood varies from one species to another while in any one species variations occur according to the age of the tree. I n addition the methoxyl content of lignin isolated in the manner already described is affected by the strength of caustic soda solution and the time and tem-perature of digestion. Lignin as isolated is therefore a mixture of methylated derivatives of a polyhydroxy-compound and i t should be possible by chemical means to effect separation into iractions of definite methoxyl content but our attempts to do so have not yet met with success. The separate fractions obtained by precipitating lignin from its solution in caustic soda by addition of hydrochloric acid gave the same figures on analysis.I n deducing the formula c4,H480,6 from the analytical results given by flax lignin and its derivatives the assumption was made that the molecule contained a definite number of methoxyl groups, vhereas in our present view there is no reason to suppose that such is the case. Instead of the total of nine hydroxyl groups indicated 11y analysis of acetyl-lignin i t is possible to suggest forrnulx! con-taining eight or ten hydroxyl groups (e.g. C,,H,,O1,) which agree equally well with the analytical data. At this stage of the work, however i t is not desirable to make a decision in favour of one or the other of these formula and until more data are available we intend to continue using the formula adopted for flax lignin, From the six wood lignins purified as described above the acetyl compounds were prepared by treatment on the steam-bath with acetic anhydride and sulphuric acid.The acetyl content varied according to the methoxyl content but in each case using the '4 5"48O 16 134 POWELL AND WHITTAKER THE CHEMISTRY OF LIGNIN. empirical formula C45H48016 as the basis of calculation the total of acetylated and methylated hydroxyl groups was nine although the actual number of methylated groups varied between three and five. All the acetyl compounds were insoluble in cold alkali and i t is therefore unlikely that there are any carboxyl groups in the molecule. The variations in methoxyl content of the various wood lignins prepared were not sufficient to affect the determinations of carbon and hydrogen which were carried out on the purified samples and the figures obtained were constant within the limits of experimental error.Table I gives a summary of the analytical results and also the number of groups calculated on the basis of the formula C4,H,,0, for the parent hydroxyl compound itself. It is proposed to assign the name ZignoZ to this compound. Substance Determin-analysed. ation. Lignin. C H CHO Acetyl-lignin. OMe COCH, No. of OMe groups. No. of COaCH groups. Total groups. Acetylmethyl- OMe No. of OMe groups. No. of COCH groups. Total groups. lignin COCH, TABLE I. Source of Lignin. r h -. Flax. Larch. Pine.Spruce. Ash. Birch. Poplar. 63.9 63.8 63.4 64.0 63.2 63.2 63.3 5.8 5.2 5.6 5.5 5-6 5.5 5-8 11.8 9.0 11-5 11.0 13.3 15.2 12.6 20.6 23.0 18.9 19.4 17-6 14.5 17.5 4.0 3.1 3.9 3-8 4.5 5.0 4.3 5.0 6-8 4.5 4.8 4.3 3.4 4.3 9.0 8.9 8.4 8.6 8.8 8.4 8.6 20-3 19.9 20.4 23.1 20.0 22.4 22.7 11.1 11.8 10.5 8.0 11.3 8.1 7.5 6.5 6.4 6.5 7.2 6.4 7.0 7.0 2.6 2.7 2.4 1.8 2.6 1.8 1.7 9.1 9-1 8.9 9.0 9.0 8.8 8.7 3.1 - 2.9 3.1 - 3.2 -The table shows that lignol from each of the wood lignins examined has the same empirical formula and the same number of hydroxyl groups as that from flax lignin. In order to verify this statement experimentally attempts have been made to isolate lignol from the various lignins by the action of hydriodic acid. However on treating lignin with hydriodic acid (d 1.7) at 130° a dark brown product which appeared to be a mixture was obtained.The main fraction of this product wm insoluble in caustic soda and cannot therefore be lignol and as the percentage of carbon found is much higher than that calculated i t appears that reduction takes place during the reaction with hydriodic acid. Confirmation of the results and conclusions drawn from the analysis of the acetylated lignins was obtained by examination of the methylated derivatives. The latter were prepared by treatment of the sodium hydroxide solution of lignin with methyl sulphate in the cold. It is not possible to methylate more than seven of the hydroxyl groups under the conditions employed an PART 11. A COMPARISOX OF LIGNINS ETC. 133 in some cases full methylation was obtained only after several treatments.The product from a single treatment however after being washed with dilute sodium hydroxide solution was acetylated in the usual manner and the total of methoxyl and acetyl groups in all the products was found t o be practically constant. It was stated in the paper on flax lignin (Zoc. cit.) that the proportion of acetyl in acetj-lmethyl-lignin was too low to account for the presence of two acetyl groups. In the experiments on vhich this statement was based acetic anhydride alone was used as the acetylating agent, but i t has since been found that in presence of sulphuric acid the diacetyl derivative is readily formed. The analytical data given in Table I for the acetylmethyl-lignins strongly support the view that all the various lignins examined have the same empirical composition and number of hydroxyl groups in the molecule.Derivatives of an entirely different character from those already described result when lignin is treated with chlorine or bromine, and if there were any fundamental differences in the molecular structure of the various lignins i t is unlikely that the same halogen-ated derivative would be obtained in each case. In our study of flax lignin we found that the chlorination or bromination product contained twelve halogen atoms and that a large quantity of hydrogen chloride or bromide was evolved during halogenation. Most of the methoxyl groups originally present in the lignin were removed chlorolignin apparently containing two and bromolignin containing only one methoxyl group.Six of the twelve chlorine atoms in flax chlorolignin were eliminated with great ease for example by clissolving the fully chlorinated derivative in cold dilute sodium hydroxide the hexachlorolignin being precipitated on acidification. Hexachlorolignin contains only one methoxyl group and therefore the fully chlorinated product dodecachloro-lignin can contain only one such group and is similar to the brorno-compound in that respect. The higher figure €or methoxyl obtained on analysis is due t o the ease with which hydrogen chloride is eliminated during estimation in the Zeisel apparatus. The Perkiii method for the determination of acetyl also gives high results in the case of acetyldodecachloroligi~in owing to the liberation of ethyl chloride.The six u-ood lignins have been brominated and subsequently acetylated . The dodecabromolignins and their acetyl derivatives 011 analysis gave results agreeing closely with those obtained from the corresponding products derived from flax lignin (Table 11). The dodecachlorolignins prepared from two wood lignins were similar in composition to flax dodecachlorolignin. A mixturc o 136 POWELL AND WHITTAKER THE CHEMISTRY OF LIGNIN. the six wood dodecachlorolignins on solution in dilute sodium hydroxide solution and reprecipitation with hydrochloric acid, gave a product comparable in all respects with flax hexachlorolignin. It may also be noted that the various acetylated dodecachlorolignins were more readily hydrolysed than the corresponding bromo-compounds a behaviour similar to that of the derivatives from flax lignin and that in all cases both acetyl derivatives were insoluble in cold sodium hydroxide solution.A third type of derivative nitrolignin has been prepared from each wood lignin and the products were identical with that from flax lignin in composition three nitro-groups having been introduced into the molecule. As in the case of flax nitrolignin a part of the nitrogen is present as organic nitrate as is evident by the fact that a proportion can be estimated by the Lunge or Schultze-Tremann method. The total nitrogen however can only be determined by the Dumas or Kjeldahl method. The nitration of lignin proceeds equally readily whether nitric acid alone (40%) or a mixture of nitric and sulphuric acids is used the products containing the same percentage of nitrogen.These facts indicate the prob-ability of the presence of aromatic nuclei in lignin. Acetylnitrolignin is soluble in cold alkalis and it is possible that nitrolignin conta,ins one or more carboxyl groups. In this connexion it may be noted that elementary analysis of the nitro-compounds shows that some oxidation has taken place in addition to nitration. Owing to the ready hydrolysis of the acetylnitrolignins it is difficult to deduce the number of hydroxyl groups in the molecule from analyses of this compound. TABLE 11. Substance analysed. Dodecabromo-lignin Acetyldodeca-bromolignin Dodecachloro-lignin Ni trolignin Hexachloro -lignin Methyl-lignin-phenylhydrazone N - 7.5* * Samples prepared from a mixture of equal quantities of the wood lignins.Source of Lignin. Detemin- -. -~ -..- ~ _ _ ation. Flax. Larch. Pine. Spruce. Ash Birch. Poplar. 28.0 28.2 - - 28.1 - -1.5 1.6 - - 1.6 - -55.2 55.0 54.8 55.2 55.1 54.7 54-9 1.8 1.6 - - - 2.4 2.1 /OMe \CO-CH 9.4 9.8 9.0 9.8 - - 9.2 {E c1 35.1 35.5 - - - 36.0 -{OMe 5.2 4.9 - - - 5.1 -50.4 50.2 - 50.6 3.8 3.8 - 3.9 4.2 4.1 4.1 - 4.3 - 4.2 3.0 3.2 2.6 3.1 3.0 3.3 -(: 50.1 49.5* 3.0 3*2* 3-45 3*5* 20.8 204* 1 :M PART 11. A COMPARISON OF LIQNINS ETC. 137 Some discussion has recently taken place in the literature as to whether or not lignin evolves furfuraldehyde on distillatmion with 12% hydrochloric acid and in view of this we have carefully examined our products using the volumetric method for the estim-ation of pentosans in wood cellulose previously described by us ( J .SOC. Chem. Ind. 1924 43 35T). Average results for the six crude lignins obtained by acidification of the alkaline liquor showed the presence of 0.9% of pentosans. This value was reduced to 0.3% by one purification from acetone and hydrochloric acid whilst, the product from a second purification gave no trace of furfur-aldehyde. We therefore regard as untenable the view of Hagglund (Cellulosechemie 1923 4 73) that lignin contains 5% of furfural-yielding carbohydrate as an integral part of the molecule. Of the sixteen oxygen atoms present in the molecule of lignin, nine are in the form of hydroxyl groups and one as an aldehyde group. The presence of the latter was indicated by measurements of the amount of Fehling’s solution reduced by lignin and was confirmed in the case of flax lignin by a volumetric determination of the amount of phenylhydrazine required to form the phenyl-hydrazone. The following experiment shows however that the monohydrazone is only formed under the mild conditions used in the volumetric method and that the rgaction can be made to proceed further. Methyl-lignin was allowed to react with a hot alcoholic solution of phenylhydrazine and the product freed from phenylhydrazine by several precipitations from acetone and hydro-chloric acid. Analysis showed that three phenylhydrazine molecules had reacted with each molecule of lignin and therefore that two ketonic groups must also be present. Methyl-lignin was used instead of lignin in order to avoid the formation of a phenyl-hydrazine ester. These results may be summarised by writing the formula for ljgnol in the extended form C,,H,,O,(CO),(CHO)(OH),. The details of. the experimental work are similar to those given in Part I for flax lignin and are therefore not repeated. The results are published by permission of the Director of Artillery, RESEARCH DEPARTMENT, to whom our thanks are due. ROYAL ARSENAL WOOLWICN. [Received October 21st 1924.

ISSN:0368-1645    

DOI:10.1039/CT9252700132

出版商:RSC    

年代:1925

数据来源: RSC

摘要:

138 ROBINSON AND BRISCOE: XXPI1.-A Redetermination of the Atomic Weight of The Inseparability of the Isotopes by Bromine. Fractional Crystallisation. By PERCY LUCOCK ROBINSON and HENRY VINCEPU'T AIRD ERISCOE. THE only precise experimental evidence in support of the generally accepted view that isotopes are inseparable by fractional crystallis-ation is the attempt by Richards and Hall ( J . Amer. Chem. Xoc., 1917 39 531) to separate thus the isotopic forms present in lead derived from Australian carnotite. Both they and Soddy (J., 1911 99 72; J . Amer. Chem. SOC. 1917 39 1614) refer to the earlier data which need not be quoted here. Richards and Hall obtained no evidence of separation by 904 effective crystallisations but their lead presented a relatively unfavourable case since it contained only about 20y0 of the heavier isotope and the nitrates of the isotopes differed in solubility by but o*7470 (Richards and Schumb J .Anzer. Chem. SOC. 1918, 40,1403). Since Aston's work has disclosed the existence of isotopes of many of the lighter elements it has become clear that cases may be found permitting a more precise test (or proof) of inseparability by fractional crystallisation. The isotopes of boron differ by 10% in atomic weight but the isotope ratio is unfavourable (approxim-ately 20% BlO and 80% Bl1) and an accurate determination of the atomic weight is both difficult and laborious. A prolonged frac-tionation of boric acid was effected but the determinations of atomic weight although they had other unexpected features o€ interest (see following paper) proved valueless for the purpose now under discussion.Bromine in the form of ammonium bromide seems to present the best test-case because (1) bromine has but two isotopes (Br79 and BrSl) present in nearly equal proportions and differing by 2.2y0 in atomic weight (2) hydrogen and nitrogen are " simple " elements and together form less than 20% of the salt (3) the atomic weight of bromine can be determined by direct and trustworthy methods and (4) ammonium bromide crystallises from water in a fashion convenient for a long series of fractionations. Therefore with the double object of making a re-determination of the atomic weight of bromine and of confirming in this more favour-able case the finding of Richards and Hall ammonium bromide was subjected to prolonged fractional crystallisation and the atomic weight of the bromine in the final head and tail fractions was deter-mined by measurement of the ratio Ag AgRr A EEDETERMIXATIOX O F THE ATORlIC WEIGHT O F SROXISE.130 Pu?<Jicatio.rz of Reagmts. T17cter.-Laboratory distilled water already free from halogen, was redistilled from a little caustic soda and potassium perman-ganate in a 10-gallon copper still through a vertical spray-trap packed with glass beads and condensed in pure tin. The first and last portions of the distillate were rejected anif the main fraction was collected and stored (for but a short time) in 'O-litre stoppered resistance glass bottles which had been n-ell cleaned steamed out and kept for months full of distilled water.Many iwphclometric tests were made but on no occasion did the water give any indication of chloride. Ammo?zin.-Ammonia gas liberated by warming the purest commercial ammonia (d = O.SSU) was dissolved in pure water, in an apparatus constructed entirely of rcsistance glass with cz ground-in leading tube. SuZpJzur Dioxide.-The gas used both for the conversicii of bromine to hydrobromic acid and for the precipitation cf silver by Stas's method was aln-ays obtained from the middle fraction of a syphon of the liquid. n'ilric Acid.-Commercial nitric acid containing o d y small traces of halogen was thrice redistilled in an apparatus constrwted of '' Duro " resistance glass with ground joints large head and tail fractions being rejected. The final main fraction tested in the ncyhelometer was free from halogens.It was kept in a resistance glass bottle having c well-ground glass stopper protected by a glass cap. Formic Acid.-The purest obtainable reagent acid was twice redistilled from a fused silica ffask having a ground-in silica con-denser and adapter. Considerable head and tad fractions were rejected in each distillation and the main fraction n-as preserved i s a stoppered silica flask. il~ag?zesin.-~lagiiesiulrz nitrate was thrice precipitated from saturated aqueous solution by excess of nitric acid filtered on porcelain dissolvcd in water and precipitated with ammonia. The hydroxide was washed by decantation filtered dried a t lOO", ignited in air in a platinum dish and finally heated at about 1000" in a current of moist pure hydrogen.Magnesia boats moulded from the pure oxide nioisteried with dilute nitric acid were ignited and used on a silica plate. Hydrochloric Acid-Coinmercial reagent acid was freed from arsenic by treatment with a copper-tin couple and distillation from copper gauze according to the method of Thorne and Jefiers Zi?ic.-A sample of granulated electrolytic zinc kindly supplied ( d ? ~ d y s t 1906 31 101). F" 140 ROBINSON AND BRISCOE : by Messrs. Brunner Mond & Co. Ltd. proved t'o be free from arsenic and was used without further purification. Hydrogen.-This gas prepared from pure hydrochloric acid, containing a little platinic chloride and pure zinc in a Kipp's apparatus passed to a purifying train the several parts of which were sealed together in which it traversed successively a 12 inch column of concentrated potassium hydroxide solution two 12 inch columns packed with broken sticks of pot'assium hydroxide and two 10 inch columns packed with phosphorus pentoxide distributed on glass wool.XiZwer.-Two samples " A " and " B," were used prepared in the same way but at different times and from different samples of commercial silver nitrate. In each case a filtered aqueous solution of silver nitrate (200 g.) was precipitated in a volume of about 20 Iitres with ammonium bisulphite according to t'he method of Stas (Briscoe J. 1915 107 69). The precipitated silver was washed six times with dilute ammonia allowed to stand over-night with ammonia washed six times with water and dried at 100".This silver in 100 g. portions was dissolved in pure nitric acid, precipitated hot with ammonium formate in a bulk of 2 litres, well washed with ammonia and water and dried first a t 100" and finally at 250" in an electrically heated covered beaker. Before weighing the silver was melted on a boat of pure magnesia in an atmosphere of hydrogen in an electrically heated silica tube furnace. The hydrogen issuing from the furnace during melting contained no impurities detectable by Marsh's test or by smell. At the end of each fusion the silver was collected into large buttons by shaking the furnace and these when cool were etched with 1 1 nitric acid well washed with water heated at 250" for 12 hours, and cooled in a desiccator over solid potassium hydroxide.The Determinatioia of Weight. All precise weighings were made on an Oertling balance con-structed specially for this work resembling in many respects the standard type known as " No. 7 S.W.," but with a beam of Firth's 36% nickel-steel having a low coefficient of expansion pan-supports of special design and a separate enclosure for the beam after the principle used by Manley (Phil. Trans. 1910 210 A 387). No proper situation giving constant temperature and freedom from vibration was available for the balance it was used on an ordinary stout wooden table in a room subject to vibration and to consider-able and rapid fluctuations of temperature. Even under these adverse conditions it gave results sufficiently precise and consistent for this work a remarkable performance which is undoubtedl A REDETERMINATION OF THE ATOMIC WEIGKT OF BRONINE.141 attributable to the special features of construction indicated above. The sensitiveness of the balance increased very slightly with the load and during all the mork here described was very nearly 100 scale divisions per milligram. In weighing by the method of oscil-lations the zero could easily be determined to the nearest half-division and the apparent weight thus ascertained with an error not exceeding 0.00001 g. A set of gold-plated brass weights with platinum fractions by Oertling and a gold 5-mg. rider were used and were calibrated to ascertain the relative weights in air on three separate occasions before and during the weighings. The corrections applied to ascertain relative weights in a vacuum were calculated using the density of air at the temperature and pressure observed during the weighing and the densities 10.49 and 6.47 for silver and silver bromide respectively.As relative weights only were desired and the inequality of the arms of the balance was very small and constant all weighings were made directly. All were made in duplicate and many in triplicate in no case did the values for the vacuum weight thus obtained differ by more than 0.00003 g., thus it seems probable that the mean values arc in error by less than this amount. Silver was weighed directly on the balance pan silver bromide was weighed in a stoppered glass bottle against a tare of thc same glass and of closely similar form volume and weight which had been treated in all respects as the bottle.The balance case contained solid caustic potash and a piece of pitchblende. The Fractional Crystallisalioiz of mtio'i/iuitL Brmtiide. As starting material commercial ammonium bromide puriss., was used. Prolonged exposure to the laboratory atmosphere and contact with glass inevitably introduce impurities compared with which those originally present are insignificant ; hence no attempt was made to ascertain the nature and amount of the latter. About 2500 g. of ammonium bromide were dissolved in hot water in such proportion that about one-half crystallised out u n cooling. Each fraction was again fractionated in a similar manner until a series of 30 fractions had been built up. Thereafter the number of fractions was kept constant and fractionation was continued in the usual way by crystallising the whole series taking away the " head '' (most soluble) mother-liquor to form part of a new fraction, transferring each of the other mother-liquors to the crystals of the next higher fraction adding water to the crystals of the " tail " (least soluble) fraction and again crystallising the whole series 142 ROBINSON AND BRISCOE: A detailed scheme of such a fractionation is given by Richards and Hall (loc.cit.). I n all 80 crystallisations of the whole series were thus made * and the total number of crystallisations including those in-volved in the establishment of the series was approximately 2700. Throughout the later part of the fractionation each fraction contained about 80 g .of ammonium bromide of which one-half was transferred a t each crystallisation. The fractions were contained in 200 C.C. conical flasks closed against dust by loose hollow glass stoppers distilled water of good quality was used for all crystal-lisations. At the end of the fractionation the extreme end fract’ions, Nos. 42 and 72 were rejected and the ammonium bromide of Nos. 43,57 and 71 the ‘‘ tail,” middle and “ head ” fractions respectively, was taken for the atomic weight determinations. PuriJication of Bromine for Analysis. The volatility of bromine and its liberation from a bromide by oxidation afford an unexceptionable means of separating it sharply from all elements other than chlorine and iodine. It is therefore with these elements which would tend t o concentrate in the tail and head fractions respectively that the scheme of purification is concerned.At the same time as it was important that the determinations on head and tail fractions should be strictly com-parable both had to receive identical treatment. Bromine is usually purified from the other halogens by applying the facts that it liberates iodine from an iodide and is itself liberated from a bromide by chlorine. Whilst in ordinary analytical work the assumption that these reactions are complete and irreversible holds well enough they are probably not so in fact (see e.g. Schuyten, Chem. Ztg. 1908 32 619). The methods usually adopted for the rigorous purification of bromine for atomic weight work (see e.g., Scott J.1900 97 614; Baxter J . Amer. Chem. Xoc. 1906 28, 1322) reject so great a proportion of the material in head and tail fractions (using “head ” and tail^' here in a chemical sense) as to ensure elimination of the other halogens but were for that reason inapplicable t o the small quantities (50-60 g. of bromine in each fraction) available for purification in this case. Therefore each fraction of ammonium bromide was evaporated t o dryness dried at 160° and weighed. A quantity of pure sodium carbonate about 5% in excess of the calculated amount dissolved in a small quantity of water was added to the bromide and the * The establishment of the series and the first 30 crystallisations thereof were carried out by Mr. T. Ranby whose valuable assistance in this tedious work w e desire t o acknowledge A REDETERMIXATION OF THE ATOMIO WEIGHT OF BROMINE.143 whole was again evaporated to dryness and fused a t about 800" in platinum in an oxidising atmosphere. Thus any organic impurities were destroyed. A solution of about 1 g. of potassium dichromate and 30 C.C. of concentrated sulphuric acid in 170 C.C. cf water was boiled vigorously for 10 minutes to expel any possible trace of halogen cooled and used to dissolve the sodium bromide from the platinum dish. This solution was transferred to the flask A of the distillation apparatus shown in Fig. 1 heated and kept boiling for about 10 minutes whilst the column B jacketed with cold water acted as a reflux condenser so that the free bromine might react with any trace of iodide present.Then the cooling was discontinued and the solution boiled until the bromine had distilled over into a flask containing pure water cooled externally by ice. Finally this flask was removed so that steam passed uncondensed right through the apparatus and carried away any residual traces of free halogen. The quantityof potassium dichromate used was calculated to displace about 2% of the total bromine and the procedure described evidently favoured the elimination therewith of any trace of iodine. After cooling the flask was detached from the apparatus and into it was introduced a further quantity of potassium dichromate ( 3 5 4 5 g.) calculated to displace about 95% of the total bromine originally present. Then A was refitted to the condenser heated very slowly a t fist using B as a reflux condenser and later distilling slowly over into a flask as already described.Thus a main fraction of bromine and bromine water was obtained under conditions favourable to the reaction of any trace of chlorine with the residual bromide in solution. As a check this solution was in each case treated with an excess of potassium dichromate and distilled a third time the liberation of 1-2 g. of bromine afforded satisfactory evidence that excess of bromide had been present during the distillation of the main fraction. Tests made with the largest (middle) fraction showed that digestion with sodium oxalate was unsatisfactory as a means of conversion to sodium bromide and that the quantities available were too small to permit a satisfactory distillation of aqueous hydrobromic acid.Therefore in working up the end fractions of ammonium bromide the main fraction of bromine from the first oxidation was converted directly to hydrobromic a,cid by the use of sulphur dioxide and the acid was subjected to a second fractional oxidation with potassium dichromate as already described. Thus it was possible to obtain in each final main fraction of the second series of oxidations about 90% of the bromine present in the original ammonium bromide. This bromine was collected in a 144 ROBINSON AND BRISCOE : excess of pure dilute aqueous ammonia and the resulting ammoniacal solution of ammonium bromide was transferred to a carefully cleaned, stoppered resistance glass bottle which was kept free from dust in a clean desiccator until required for analysis.Method of Anal@. To avoid the uncertainty attendant on drying and weighing ammonium bromide the ratio chosen for measurement was that of silver to silver bromide. A dilute aqueous solution of silver nitrate, made from an accurately known weight of silver was precipitated with a slight excess of ammonium bromide and the silver bromide was washed collected dried and weighed. FIG. 1. FIG. 2. FIG. 3. FIG. 4. FIG. 6. Platinum Gooch-Munroe crucibles were not available so another method of collecting the precipitate was scught and as any trans-ference is attended by risk of loss and is a source of doubt and anxiety it seemed desirable if possible to collect and weigh the precipitate in the vessel in which it is formed but at the same time to avoid any weighing of large glass vessels.After several attempts, a satisfactory method was evolved whereby the precipitate was collected in a detachable part of a suitably shaped precipitation flask shown in Figs. 2 and 3. A conical flask A of about 1700 C.C. capacity has two necks B and C fitted with hollow glass stoppers; the neck C has also an external taper both this and the stopper D being ground info the neck of the weighing bottle E. Four such flasks a.nd two spare weighing bottles with stoppers for use as tares were made of " Durosil " glass the joints and stoppers being very carefully ground and polished to an excellent fit * the various parts of each set * Our thanks are due to Mr. G. Ellison of this Department for his care arid skill in executing this difficult task A REDETERMINATION OF THE ATOMIC WEIGHT OF BIJOMIEU'E.145 mere etched with the same number. Before use the flasks and bottles were cleaned with chromic and nitric acids washed allowed t'o stand about three weeks containing a solution of arnmoniuni bromide and nitric acid allowed to soak for a further period in distilled water and well washed. In conducting a precipitation several buttons of pure silver, weighing about 4-5 g. were weighed and dissolved in pure nitric acid in a solution flask of the form previously described (Briscce, J. 1915 107 78) and the solution was boiled to expel nitrous fumes cooled and diluted with pure water to about 400 C.C. Mean-wli ile a measured volume of ammonium bromide solution COE-taining bromine abcut 5% in excessof that required by this silver, was acidified with pure nitric acid diluted to about 700 c.c.and filtered into the precipitation flask supported by a padded ring and resting on a pad of filter paper F in the position shown in Fig. 2. All succeeding operations up to and including the final weigliings were conducted in orange light in a darkened laboratory set aside for this work. A rapid rotary movement was given to the bromide solution the silver solution was poured into i t with all the usual pre-cautions to avoid loss and 6-43 rinsings of the solution flask followed, bringing the total bulk in the precipitation flask to about 1400 C.C. Then the flask was stoppered and vigorously shaken a t first every 30 mins.and later about twice a day. After 7 days the precipitate having become sufficiently dense and coherent for transference, the stopper C was removed and rinsed into the flask and the super-nat'ant liquor was syphoned off by means of the arrangement deseribcd later. By careful manipulation the liquor left ahove the precipitate was reduced to 2-3 C.C. Next the silver bromide was washed twice by decantation using in each case ahout 1000 c.c. of wash-water allowing the precipitate to settle 2-3 days and syphoning off as in the first case. Com-monly the precipitate tended to form a colloidal solution in the seccncl wash and a solution of about 0.5 g. of ammonium nitrate, prepared from pure ammonia and nitric acid was added to avoid this difficulty. Transference of the precipitate to the weighing bottle was e€fected by means of the second washing.The bottle having been carefully heated in dry air cooled and weighed against the tare was fitted t o the aask at C and by reversing the whole apparatus into the position shown in Fig. 3 and alternately giving a rotary agitation ajnd allowing the apparatus to stand the silver bromide '~~'tls washed down into E. Then the stoppcr B was removed the wash-water syphoned off the syphon tube and the wails of the flask were rinsed down with a fine jet of water and the wash was syphoned off 146 ROBINSON AND BRISCOE : Finally the syphon was partly withdrawn i t and the flask were again rinsed the bottle was detached and the neck C rinsed into it. The bottle containing the silver bromide with but 15-20 C.C.of water was then heated in an electrically heated sheet nickel air-bath, h t at 85-90" until all free water had evaporated and then,at about 250-300" for 12-14 hours. During the whole of this drying operation a current of air supplied by a water-blast and dried by passing through a glass train over sulphuric acid concentrated aqueous potassium hydroxide and solid potassium hydroxide successively was led into the bottle by a glass tube inserted through the lid of the oven. The tare was of course heated alongside the bottle and after cooling usually for 3 4 hours in the current of dry air both bottle and tare were stoppered transferred to the balance case and weighed. The heating and weighing were repeated once or twice to ensure that a constant weight had been attained.I n two of the preliminary experiments the silver bromide was afterwards fused in the bottle heated in a small vertical electric furnace of silica provided with a window to allow observation of the fusion. As this treatment had no appreciable effect upon the apparent weight it was omitted in the final analyses. To minimise the risk of appreciable solvent action on the bottles, care was taken that they were never in contact with washings for more than 12 hours. There remains the risk of mechanical loss of glass from the ground joint; although Richards has shown that with a well made and carefullyused joint this risk is small. For-tunately satisfactory evidence that both these effects were negligible in the present work is afforded by comparing the weights of three of the bottles (weighed against the same tare) before and after the first series of precipitations :-Bottle I.Bottle 11. Bottle 111. Apparent wt. before ......... 2.02985 2-22330 3.22 103 ) , after ......... 2.02987 2.22330 3.22104 Before the method above described was finally adopted attempts were made to find a substitute for the Gooch-Munroe crucible which may be recorded briefly here. An alundum crucible was digested with 1 2 nitric acid for 6 horns and with repeated changes of water for 24 hours washed thoroughly with water under suction dried at 130" for 10 hours and ignited to about 600" in a closed porcelain crucible. After cooling in a desiccator and standing on the balance pan for 30 minutes the crucible had a weight of 12.47830 g.Then a litre of a clear filtered solution of 20 Q. of ammonium bromide in 10% nitric acid was passed through the crucible and it was washed and dried as before when its weight was 12.47799 g. (loss 0.30 mg.). A repetition of the treatment reduced the weight t A REDETEEMINATIOS O F TI-IE BTOA'IIC WEIGHT OF BROMINE. 147 12.47'782 g. (loss 0-17 mg.) and a second repetition using 5% nitric acid caused a further change t o 12.47746 g. (loss 0.36 mg.). Thus, evidently there was a continuous and variable loss too great to permit tlie successful use of alundum crucibles. A Jena filter crucible having a mat of sintered glass similarly treated but dried for 14 hours a t 350" lost in weight 0.80 mg. and among several such crucibles i t was observed that the degree of fritting was not uniform, some mats being so friable that glass could be removed with the finger nail.Hence such crucibles too were dismissed its unsuitable. The device used in syphoning the liquors and washings may here be described. Prelimiiiary experiments showed that as the liquid level fell fine particles of precipitate were apt to be dislodged from the sides of the flask and carried over with the washings. It vas impracticable to reduce the syphon to a capillary fine enougli to stop these particles therefore although tlie syphon was never brought in contact with the mass of the precipitate some form of reverse filter was necessary. Disks of thin alundum or wads of spongy platinum fused into the ends of glass tubes proved much too slow but a porous glass filter of the form shown in Fig.4 proved satisfactory. It was made by taking powdered Dixosil glass passing a sieve of 100 meshes to the linear inch and retained on zt 200 mesh sieve cleaning the powder by boiling ixith hydrochloric acid and washing with water packing i t wet to form a 3 mm. layer in the end of a 12 mm. bore Durosil tube and then drjing at 100" and heating carefully in a luminous flarre until the glass sintered to a strong coherent yet porous mass adhering firmly to the tube. After experience had been gained it was possiblc thus to make filters which n-ould pass 1000-1500 C.C. of n-atcr per hour nith a pressure difference of 3 0 4 0 cm. of mercury and yet' retain the iincst partic-lcs of suspended matter. Each filter was fused to a long tube and then carefully cleaned ant1 soaked.I n use it was connected by a length of clean pure rubber pressure-tubing to a clean bottle in nhich the liquors were received in the manner shown in Fig. 5. In each analysis the fist mother-liquor was tested to ensure that an excess of bromide had been used as nephelometric tests gave in them no indication of silver they were rejected. Some small particles of silver bromide adhered to the inner surface of the precipitation flask or were retained by the glass filter therefore one filter was kept for each analysis and after the bottle and precipi-tate had been removed the flask was stoppered at B and re-inverted, and a small quantity of pure ammonia was passed in the reverse direction through the filter shaken round the walls of the flask and, with the rinsings of filter and flask made up to a definite bulk 148 ROBINSON AND BRISCOE : The silver content of this solution and of the main washings was then determined by nephelometric comparison of aliquot portions with standard silver solutions and the weight of silver 'lost thus ascertained was deducted from the weight of silver originally taken.Statement and Discussion of Results. Several preliminary analyses made on the middle fraction of ammonium bromide No. 57 whilst useful in establishing the methods are not comparable in value with those of the final series : hence the results are omitted here. The final series consisted of eight determinations four on the ammonium bromide from the head fraction No.71 and four on t,hat from the tail fraction No. 43. The essenthl data are given in Table I. TABLE I. Scries I . 1 71 A 3.69325 2 , , 5.06115 3 , , 3-93515 4 ? , 3.67332 Serie.9 I I . 5 43 A 5-14730 6 ,? 3.08140 7 , B 3.34631 S , , 3.43817 0.00058 3-69267 6.42874 0-00297 5.05818 8.80494 0.00374 3.93141 6.84337 0.00097 3.67235 6.39249 Mean of Series I. 0.00146 5-14584 8.95708 0.00111 3.08029 5-36261 0-00072 3.34559 5.82369 0.00251 3-43566 5.98102 Mean of Series 11. General mean 0,574400 79-933 0.574471 79.910 0.574484 79.906 0.574479 79.908 0.574459 79.914 0.574499 79.901 0.574401 79-933 0.574479 79.907 0.574427 79.916 0.574451 79.914 0.574455 79.914 +0.019 - 0.004 -0.00s -0.006 & 0.009 -0.013 + 0.01 7 - 0.009 + 0-002 fO.011 &0.010 In the first group of analyses the extreme variation in the ratio Ag AgBr is 0.000084 or 1 part in 6840 that in the atomic weight of bromine is 0.027 or 1 part in 2990.In the second group t.he cor-responding variations are 0-000096 or 1 part in 5984 and 0.032 or 1 part in 2493. The magnitude and sign of these variations indicate that the mean value of the atomic weight deduced from each series has an error probably less than 0.01 or in round numbers, about 1 part in 8000. The mean atomic weights from the two series differ by but 1 part in 40,000 as a change of lye in the isotope ratio would change the atomic weight by 0.02 and should have been appreciable in these determinations it appears that a fractionation of ammonium bromide involving 2700 crystallisations does not produce such a change.This result affording as it does more precise confirmation of th A REDETERMINATION OF THE ATOMIC WEIGHT OF BROMINE. 149 conclusion drawn by Richards and Hall is of some theoretical interest. It is in particular instructive to institute a comparison between t'he present results and those recorded for salts of kindred rare-earths where the solubility differences are of the same order. The solubilities of the hexahydrated nitrates of lanthanum and neodymium La(NB,),,6H20 and Nd(N0,),,6H20 are respect-ively 151.1 and 152.9 parts of anhydrous nitrate in 100 parts of water (James and Whittemore J . Amer. Chem. Xoc. 1912 34, 1168; James and Robinson ibid. 1913,35 754).As the molecular weights are 324.8 (La = 138-8) and 330-2 (Nd = 144.2) the mole-cular solubilities are 0,46520 and 0.46515. The coincidence of these numbers within one part in 9000 is obviously accidental but the molecular solubilities evidently differ by no more than the error of the solubility determinations say 2 or 3 parts in 1000 parts. The effect of fractional crystallisation in this case is shown in t'he investigations inter alios of Demargay (Cmpt. rend. 1896 122, 728; 1900 130 1021) and of Baxter and Chapin ( J . Amer. Chem. Soc. 1911 33 1). In the latter case for example about 1600 crystallisations as double ammonium nitrates and aboutl 1300 as simple nitrates produced a number of fractions of neodymium free from appreciable traces of other earths.The fact that 2000 crystallisations or fewer completely separate these earths whilst more than 2500 crystallisations do not appreci-ably change the proportions of the two kinds of molecule in ammon-ium bromide may be explained by and therefore affords chemical evidence supporting the theories of Bohr and of Bury (J. Amer. Chem. Xoc. 1921 43 1602) whereby the additional electrons in the atom of the heavier of a pair of rare-earth metals are supposed to be less intimately associated with the corresponding protons than are the additional electrons in the heavier of a pair of isotopes. Regarding the data as one series of determinations of the atomic weight of bromine it is to be noted that the extreme variation in the ratio Ag AgBr is from 0-574400 to 0.574498 or 1 part in 5745, whilst that in the atomic weight is from 79.901 to 79-933 or 1 part in 2500.The general mean values are given in Table I. A discussion of all the available data for the ratio of silver to silver bromide both direct and indirect has been given by Clarke (" A Recalculation of the Atomic Weights," 4th Edition Mem. Nnt. Acud. Sci. 1920 16 71) and need not be attempted here. The best direct determinations are those of Baxter (J. Amer. Chem. Soc., 1906 28 1322) whose general mean of 18 determinations of the ratio Ag AgBr is 0-57445 a figure substantially identical with that calculated by Clarke as the general mean of all determinations. Possible sources of error in the present determinations are 150 BRISCOE ROBINSON AND STEPHENSON : (1) errors in weighing ; (2) loss of silver in transference ; (3) impurity in the silver; (4) loss of silver bromide mechanically or in solution; (5) the presence of chlorine or iodine in the ammonium bromide.The error in weighing was undoubtedly too small to have any signifi-cant effect and the mode of transference of silver solution to the precipitation flask would appear to eliminate any risk of mechanical loss. The methods used for the preparation of pure silver have been shown to yield a metal containing less than 1 part of impurity in 300,000 parts of silver (Briscoe and Little J. 1914 105 1320). There can be little doubt that the chief error in the determination of weight lay in the nephelometric estimation of the silver lost (4) in washings and retained by the flask and filter a careful review of the analytical details leads to the conclusion that this error was not greater than 0.0001 g.but it was probably the one really significant error in the determinatioiis. With regard to the purity of the bromine it is certain that in such a prolonged fractionation the whole of any chlorine and iodine originally present would have become concentrated in opposite end fractions therefore the identity of the results obtained with these fractions shows that the chemical purification subsequent to fractionation had so far reduced the proportion of these halogens that their effect on the atomic weight of bromine was inappreciable. The final mean value of the ratio Ag AgBr now found differs from Baxter’s value by less than 1 part in 100,000 and the rounded mean value of the atomic weight Br = 79.92 with a probable error & 0.0031 confirms the accepted atomic weight.UNIVERSITY OF DURHAM ARMSTRONG COLLEGE, NEWCASTLE UPON TYNE. [Received November 3rd 1924. 138 ROBINSON AND BRISCOE: XXPI1.-A Redetermination of the Atomic Weight of The Inseparability of the Isotopes by Bromine. Fractional Crystallisation. By PERCY LUCOCK ROBINSON and HENRY VINCEPU'T AIRD ERISCOE. THE only precise experimental evidence in support of the generally accepted view that isotopes are inseparable by fractional crystallis-ation is the attempt by Richards and Hall ( J . Amer. Chem. Xoc., 1917 39 531) to separate thus the isotopic forms present in lead derived from Australian carnotite. Both they and Soddy (J., 1911 99 72; J .Amer. Chem. SOC. 1917 39 1614) refer to the earlier data which need not be quoted here. Richards and Hall obtained no evidence of separation by 904 effective crystallisations but their lead presented a relatively unfavourable case since it contained only about 20y0 of the heavier isotope and the nitrates of the isotopes differed in solubility by but o*7470 (Richards and Schumb J . Anzer. Chem. SOC. 1918, 40,1403). Since Aston's work has disclosed the existence of isotopes of many of the lighter elements it has become clear that cases may be found permitting a more precise test (or proof) of inseparability by fractional crystallisation. The isotopes of boron differ by 10% in atomic weight but the isotope ratio is unfavourable (approxim-ately 20% BlO and 80% Bl1) and an accurate determination of the atomic weight is both difficult and laborious.A prolonged frac-tionation of boric acid was effected but the determinations of atomic weight although they had other unexpected features o€ interest (see following paper) proved valueless for the purpose now under discussion. Bromine in the form of ammonium bromide seems to present the best test-case because (1) bromine has but two isotopes (Br79 and BrSl) present in nearly equal proportions and differing by 2.2y0 in atomic weight (2) hydrogen and nitrogen are " simple " elements and together form less than 20% of the salt (3) the atomic weight of bromine can be determined by direct and trustworthy methods and (4) ammonium bromide crystallises from water in a fashion convenient for a long series of fractionations.Therefore with the double object of making a re-determination of the atomic weight of bromine and of confirming in this more favour-able case the finding of Richards and Hall ammonium bromide was subjected to prolonged fractional crystallisation and the atomic weight of the bromine in the final head and tail fractions was deter-mined by measurement of the ratio Ag AgRr A EEDETERMIXATIOX O F THE ATORlIC WEIGHT O F SROXISE. 130 Pu?<Jicatio.rz of Reagmts. T17cter.-Laboratory distilled water already free from halogen, was redistilled from a little caustic soda and potassium perman-ganate in a 10-gallon copper still through a vertical spray-trap packed with glass beads and condensed in pure tin.The first and last portions of the distillate were rejected anif the main fraction was collected and stored (for but a short time) in 'O-litre stoppered resistance glass bottles which had been n-ell cleaned steamed out and kept for months full of distilled water. Many iwphclometric tests were made but on no occasion did the water give any indication of chloride. Ammo?zin.-Ammonia gas liberated by warming the purest commercial ammonia (d = O.SSU) was dissolved in pure water, in an apparatus constructed entirely of rcsistance glass with cz ground-in leading tube. SuZpJzur Dioxide.-The gas used both for the conversicii of bromine to hydrobromic acid and for the precipitation cf silver by Stas's method was aln-ays obtained from the middle fraction of a syphon of the liquid.n'ilric Acid.-Commercial nitric acid containing o d y small traces of halogen was thrice redistilled in an apparatus constrwted of '' Duro " resistance glass with ground joints large head and tail fractions being rejected. The final main fraction tested in the ncyhelometer was free from halogens. It was kept in a resistance glass bottle having c well-ground glass stopper protected by a glass cap. Formic Acid.-The purest obtainable reagent acid was twice redistilled from a fused silica ffask having a ground-in silica con-denser and adapter. Considerable head and tad fractions were rejected in each distillation and the main fraction n-as preserved i s a stoppered silica flask. il~ag?zesin.-~lagiiesiulrz nitrate was thrice precipitated from saturated aqueous solution by excess of nitric acid filtered on porcelain dissolvcd in water and precipitated with ammonia.The hydroxide was washed by decantation filtered dried a t lOO", ignited in air in a platinum dish and finally heated at about 1000" in a current of moist pure hydrogen. Magnesia boats moulded from the pure oxide nioisteried with dilute nitric acid were ignited and used on a silica plate. Hydrochloric Acid-Coinmercial reagent acid was freed from arsenic by treatment with a copper-tin couple and distillation from copper gauze according to the method of Thorne and Jefiers Zi?ic.-A sample of granulated electrolytic zinc kindly supplied ( d ? ~ d y s t 1906 31 101). F" 140 ROBINSON AND BRISCOE : by Messrs. Brunner Mond & Co. Ltd.proved t'o be free from arsenic and was used without further purification. Hydrogen.-This gas prepared from pure hydrochloric acid, containing a little platinic chloride and pure zinc in a Kipp's apparatus passed to a purifying train the several parts of which were sealed together in which it traversed successively a 12 inch column of concentrated potassium hydroxide solution two 12 inch columns packed with broken sticks of pot'assium hydroxide and two 10 inch columns packed with phosphorus pentoxide distributed on glass wool. XiZwer.-Two samples " A " and " B," were used prepared in the same way but at different times and from different samples of commercial silver nitrate. In each case a filtered aqueous solution of silver nitrate (200 g.) was precipitated in a volume of about 20 Iitres with ammonium bisulphite according to t'he method of Stas (Briscoe J.1915 107 69). The precipitated silver was washed six times with dilute ammonia allowed to stand over-night with ammonia washed six times with water and dried at 100". This silver in 100 g. portions was dissolved in pure nitric acid, precipitated hot with ammonium formate in a bulk of 2 litres, well washed with ammonia and water and dried first a t 100" and finally at 250" in an electrically heated covered beaker. Before weighing the silver was melted on a boat of pure magnesia in an atmosphere of hydrogen in an electrically heated silica tube furnace. The hydrogen issuing from the furnace during melting contained no impurities detectable by Marsh's test or by smell.At the end of each fusion the silver was collected into large buttons by shaking the furnace and these when cool were etched with 1 1 nitric acid well washed with water heated at 250" for 12 hours, and cooled in a desiccator over solid potassium hydroxide. The Determinatioia of Weight. All precise weighings were made on an Oertling balance con-structed specially for this work resembling in many respects the standard type known as " No. 7 S.W.," but with a beam of Firth's 36% nickel-steel having a low coefficient of expansion pan-supports of special design and a separate enclosure for the beam after the principle used by Manley (Phil. Trans. 1910 210 A 387). No proper situation giving constant temperature and freedom from vibration was available for the balance it was used on an ordinary stout wooden table in a room subject to vibration and to consider-able and rapid fluctuations of temperature.Even under these adverse conditions it gave results sufficiently precise and consistent for this work a remarkable performance which is undoubtedl A REDETERMINATION OF THE ATOMIC WEIGKT OF BRONINE. 141 attributable to the special features of construction indicated above. The sensitiveness of the balance increased very slightly with the load and during all the mork here described was very nearly 100 scale divisions per milligram. In weighing by the method of oscil-lations the zero could easily be determined to the nearest half-division and the apparent weight thus ascertained with an error not exceeding 0.00001 g.A set of gold-plated brass weights with platinum fractions by Oertling and a gold 5-mg. rider were used and were calibrated to ascertain the relative weights in air on three separate occasions before and during the weighings. The corrections applied to ascertain relative weights in a vacuum were calculated using the density of air at the temperature and pressure observed during the weighing and the densities 10.49 and 6.47 for silver and silver bromide respectively. As relative weights only were desired and the inequality of the arms of the balance was very small and constant all weighings were made directly. All were made in duplicate and many in triplicate in no case did the values for the vacuum weight thus obtained differ by more than 0.00003 g., thus it seems probable that the mean values arc in error by less than this amount.Silver was weighed directly on the balance pan silver bromide was weighed in a stoppered glass bottle against a tare of thc same glass and of closely similar form volume and weight which had been treated in all respects as the bottle. The balance case contained solid caustic potash and a piece of pitchblende. The Fractional Crystallisalioiz of mtio'i/iuitL Brmtiide. As starting material commercial ammonium bromide puriss., was used. Prolonged exposure to the laboratory atmosphere and contact with glass inevitably introduce impurities compared with which those originally present are insignificant ; hence no attempt was made to ascertain the nature and amount of the latter.About 2500 g. of ammonium bromide were dissolved in hot water in such proportion that about one-half crystallised out u n cooling. Each fraction was again fractionated in a similar manner until a series of 30 fractions had been built up. Thereafter the number of fractions was kept constant and fractionation was continued in the usual way by crystallising the whole series taking away the " head '' (most soluble) mother-liquor to form part of a new fraction, transferring each of the other mother-liquors to the crystals of the next higher fraction adding water to the crystals of the " tail " (least soluble) fraction and again crystallising the whole series 142 ROBINSON AND BRISCOE: A detailed scheme of such a fractionation is given by Richards and Hall (loc. cit.).I n all 80 crystallisations of the whole series were thus made * and the total number of crystallisations including those in-volved in the establishment of the series was approximately 2700. Throughout the later part of the fractionation each fraction contained about 80 g . of ammonium bromide of which one-half was transferred a t each crystallisation. The fractions were contained in 200 C.C. conical flasks closed against dust by loose hollow glass stoppers distilled water of good quality was used for all crystal-lisations. At the end of the fractionation the extreme end fract’ions, Nos. 42 and 72 were rejected and the ammonium bromide of Nos. 43,57 and 71 the ‘‘ tail,” middle and “ head ” fractions respectively, was taken for the atomic weight determinations.PuriJication of Bromine for Analysis. The volatility of bromine and its liberation from a bromide by oxidation afford an unexceptionable means of separating it sharply from all elements other than chlorine and iodine. It is therefore with these elements which would tend t o concentrate in the tail and head fractions respectively that the scheme of purification is concerned. At the same time as it was important that the determinations on head and tail fractions should be strictly com-parable both had to receive identical treatment. Bromine is usually purified from the other halogens by applying the facts that it liberates iodine from an iodide and is itself liberated from a bromide by chlorine. Whilst in ordinary analytical work the assumption that these reactions are complete and irreversible holds well enough they are probably not so in fact (see e.g.Schuyten, Chem. Ztg. 1908 32 619). The methods usually adopted for the rigorous purification of bromine for atomic weight work (see e.g., Scott J. 1900 97 614; Baxter J . Amer. Chem. Xoc. 1906 28, 1322) reject so great a proportion of the material in head and tail fractions (using “head ” and tail^' here in a chemical sense) as to ensure elimination of the other halogens but were for that reason inapplicable t o the small quantities (50-60 g. of bromine in each fraction) available for purification in this case. Therefore each fraction of ammonium bromide was evaporated t o dryness dried at 160° and weighed. A quantity of pure sodium carbonate about 5% in excess of the calculated amount dissolved in a small quantity of water was added to the bromide and the * The establishment of the series and the first 30 crystallisations thereof were carried out by Mr.T. Ranby whose valuable assistance in this tedious work w e desire t o acknowledge A REDETERMIXATION OF THE ATOMIO WEIGHT OF BROMINE. 143 whole was again evaporated to dryness and fused a t about 800" in platinum in an oxidising atmosphere. Thus any organic impurities were destroyed. A solution of about 1 g. of potassium dichromate and 30 C.C. of concentrated sulphuric acid in 170 C.C. cf water was boiled vigorously for 10 minutes to expel any possible trace of halogen cooled and used to dissolve the sodium bromide from the platinum dish. This solution was transferred to the flask A of the distillation apparatus shown in Fig.1 heated and kept boiling for about 10 minutes whilst the column B jacketed with cold water acted as a reflux condenser so that the free bromine might react with any trace of iodide present. Then the cooling was discontinued and the solution boiled until the bromine had distilled over into a flask containing pure water cooled externally by ice. Finally this flask was removed so that steam passed uncondensed right through the apparatus and carried away any residual traces of free halogen. The quantityof potassium dichromate used was calculated to displace about 2% of the total bromine and the procedure described evidently favoured the elimination therewith of any trace of iodine. After cooling the flask was detached from the apparatus and into it was introduced a further quantity of potassium dichromate ( 3 5 4 5 g.) calculated to displace about 95% of the total bromine originally present.Then A was refitted to the condenser heated very slowly a t fist using B as a reflux condenser and later distilling slowly over into a flask as already described. Thus a main fraction of bromine and bromine water was obtained under conditions favourable to the reaction of any trace of chlorine with the residual bromide in solution. As a check this solution was in each case treated with an excess of potassium dichromate and distilled a third time the liberation of 1-2 g. of bromine afforded satisfactory evidence that excess of bromide had been present during the distillation of the main fraction.Tests made with the largest (middle) fraction showed that digestion with sodium oxalate was unsatisfactory as a means of conversion to sodium bromide and that the quantities available were too small to permit a satisfactory distillation of aqueous hydrobromic acid. Therefore in working up the end fractions of ammonium bromide the main fraction of bromine from the first oxidation was converted directly to hydrobromic a,cid by the use of sulphur dioxide and the acid was subjected to a second fractional oxidation with potassium dichromate as already described. Thus it was possible to obtain in each final main fraction of the second series of oxidations about 90% of the bromine present in the original ammonium bromide. This bromine was collected in a 144 ROBINSON AND BRISCOE : excess of pure dilute aqueous ammonia and the resulting ammoniacal solution of ammonium bromide was transferred to a carefully cleaned, stoppered resistance glass bottle which was kept free from dust in a clean desiccator until required for analysis.Method of Anal@. To avoid the uncertainty attendant on drying and weighing ammonium bromide the ratio chosen for measurement was that of silver to silver bromide. A dilute aqueous solution of silver nitrate, made from an accurately known weight of silver was precipitated with a slight excess of ammonium bromide and the silver bromide was washed collected dried and weighed. FIG. 1. FIG. 2. FIG. 3. FIG. 4. FIG. 6. Platinum Gooch-Munroe crucibles were not available so another method of collecting the precipitate was scught and as any trans-ference is attended by risk of loss and is a source of doubt and anxiety it seemed desirable if possible to collect and weigh the precipitate in the vessel in which it is formed but at the same time to avoid any weighing of large glass vessels.After several attempts, a satisfactory method was evolved whereby the precipitate was collected in a detachable part of a suitably shaped precipitation flask shown in Figs. 2 and 3. A conical flask A of about 1700 C.C. capacity has two necks B and C fitted with hollow glass stoppers; the neck C has also an external taper both this and the stopper D being ground info the neck of the weighing bottle E. Four such flasks a.nd two spare weighing bottles with stoppers for use as tares were made of " Durosil " glass the joints and stoppers being very carefully ground and polished to an excellent fit * the various parts of each set * Our thanks are due to Mr.G. Ellison of this Department for his care arid skill in executing this difficult task A REDETERMINATION OF THE ATOMIC WEIGHT OF BIJOMIEU'E. 145 mere etched with the same number. Before use the flasks and bottles were cleaned with chromic and nitric acids washed allowed t'o stand about three weeks containing a solution of arnmoniuni bromide and nitric acid allowed to soak for a further period in distilled water and well washed. In conducting a precipitation several buttons of pure silver, weighing about 4-5 g. were weighed and dissolved in pure nitric acid in a solution flask of the form previously described (Briscce, J.1915 107 78) and the solution was boiled to expel nitrous fumes cooled and diluted with pure water to about 400 C.C. Mean-wli ile a measured volume of ammonium bromide solution COE-taining bromine abcut 5% in excessof that required by this silver, was acidified with pure nitric acid diluted to about 700 c.c. and filtered into the precipitation flask supported by a padded ring and resting on a pad of filter paper F in the position shown in Fig. 2. All succeeding operations up to and including the final weigliings were conducted in orange light in a darkened laboratory set aside for this work. A rapid rotary movement was given to the bromide solution the silver solution was poured into i t with all the usual pre-cautions to avoid loss and 6-43 rinsings of the solution flask followed, bringing the total bulk in the precipitation flask to about 1400 C.C.Then the flask was stoppered and vigorously shaken a t first every 30 mins. and later about twice a day. After 7 days the precipitate having become sufficiently dense and coherent for transference, the stopper C was removed and rinsed into the flask and the super-nat'ant liquor was syphoned off by means of the arrangement deseribcd later. By careful manipulation the liquor left ahove the precipitate was reduced to 2-3 C.C. Next the silver bromide was washed twice by decantation using in each case ahout 1000 c.c. of wash-water allowing the precipitate to settle 2-3 days and syphoning off as in the first case.Com-monly the precipitate tended to form a colloidal solution in the seccncl wash and a solution of about 0.5 g. of ammonium nitrate, prepared from pure ammonia and nitric acid was added to avoid this difficulty. Transference of the precipitate to the weighing bottle was e€fected by means of the second washing. The bottle having been carefully heated in dry air cooled and weighed against the tare was fitted t o the aask at C and by reversing the whole apparatus into the position shown in Fig. 3 and alternately giving a rotary agitation ajnd allowing the apparatus to stand the silver bromide '~~'tls washed down into E. Then the stoppcr B was removed the wash-water syphoned off the syphon tube and the wails of the flask were rinsed down with a fine jet of water and the wash was syphoned off 146 ROBINSON AND BRISCOE : Finally the syphon was partly withdrawn i t and the flask were again rinsed the bottle was detached and the neck C rinsed into it.The bottle containing the silver bromide with but 15-20 C.C. of water was then heated in an electrically heated sheet nickel air-bath, h t at 85-90" until all free water had evaporated and then,at about 250-300" for 12-14 hours. During the whole of this drying operation a current of air supplied by a water-blast and dried by passing through a glass train over sulphuric acid concentrated aqueous potassium hydroxide and solid potassium hydroxide successively was led into the bottle by a glass tube inserted through the lid of the oven. The tare was of course heated alongside the bottle and after cooling usually for 3 4 hours in the current of dry air both bottle and tare were stoppered transferred to the balance case and weighed.The heating and weighing were repeated once or twice to ensure that a constant weight had been attained. I n two of the preliminary experiments the silver bromide was afterwards fused in the bottle heated in a small vertical electric furnace of silica provided with a window to allow observation of the fusion. As this treatment had no appreciable effect upon the apparent weight it was omitted in the final analyses. To minimise the risk of appreciable solvent action on the bottles, care was taken that they were never in contact with washings for more than 12 hours. There remains the risk of mechanical loss of glass from the ground joint; although Richards has shown that with a well made and carefullyused joint this risk is small.For-tunately satisfactory evidence that both these effects were negligible in the present work is afforded by comparing the weights of three of the bottles (weighed against the same tare) before and after the first series of precipitations :-Bottle I. Bottle 11. Bottle 111. Apparent wt. before ......... 2.02985 2-22330 3.22 103 ) , after ......... 2.02987 2.22330 3.22104 Before the method above described was finally adopted attempts were made to find a substitute for the Gooch-Munroe crucible which may be recorded briefly here. An alundum crucible was digested with 1 2 nitric acid for 6 horns and with repeated changes of water for 24 hours washed thoroughly with water under suction dried at 130" for 10 hours and ignited to about 600" in a closed porcelain crucible.After cooling in a desiccator and standing on the balance pan for 30 minutes the crucible had a weight of 12.47830 g. Then a litre of a clear filtered solution of 20 Q. of ammonium bromide in 10% nitric acid was passed through the crucible and it was washed and dried as before when its weight was 12.47799 g. (loss 0.30 mg.). A repetition of the treatment reduced the weight t A REDETEEMINATIOS O F TI-IE BTOA'IIC WEIGHT OF BROMINE. 147 12.47'782 g. (loss 0-17 mg.) and a second repetition using 5% nitric acid caused a further change t o 12.47746 g. (loss 0.36 mg.). Thus, evidently there was a continuous and variable loss too great to permit tlie successful use of alundum crucibles.A Jena filter crucible having a mat of sintered glass similarly treated but dried for 14 hours a t 350" lost in weight 0.80 mg. and among several such crucibles i t was observed that the degree of fritting was not uniform, some mats being so friable that glass could be removed with the finger nail. Hence such crucibles too were dismissed its unsuitable. The device used in syphoning the liquors and washings may here be described. Prelimiiiary experiments showed that as the liquid level fell fine particles of precipitate were apt to be dislodged from the sides of the flask and carried over with the washings. It vas impracticable to reduce the syphon to a capillary fine enougli to stop these particles therefore although tlie syphon was never brought in contact with the mass of the precipitate some form of reverse filter was necessary.Disks of thin alundum or wads of spongy platinum fused into the ends of glass tubes proved much too slow but a porous glass filter of the form shown in Fig. 4 proved satisfactory. It was made by taking powdered Dixosil glass passing a sieve of 100 meshes to the linear inch and retained on zt 200 mesh sieve cleaning the powder by boiling ixith hydrochloric acid and washing with water packing i t wet to form a 3 mm. layer in the end of a 12 mm. bore Durosil tube and then drjing at 100" and heating carefully in a luminous flarre until the glass sintered to a strong coherent yet porous mass adhering firmly to the tube.After experience had been gained it was possiblc thus to make filters which n-ould pass 1000-1500 C.C. of n-atcr per hour nith a pressure difference of 3 0 4 0 cm. of mercury and yet' retain the iincst partic-lcs of suspended matter. Each filter was fused to a long tube and then carefully cleaned ant1 soaked. I n use it was connected by a length of clean pure rubber pressure-tubing to a clean bottle in nhich the liquors were received in the manner shown in Fig. 5. In each analysis the fist mother-liquor was tested to ensure that an excess of bromide had been used as nephelometric tests gave in them no indication of silver they were rejected. Some small particles of silver bromide adhered to the inner surface of the precipitation flask or were retained by the glass filter therefore one filter was kept for each analysis and after the bottle and precipi-tate had been removed the flask was stoppered at B and re-inverted, and a small quantity of pure ammonia was passed in the reverse direction through the filter shaken round the walls of the flask and, with the rinsings of filter and flask made up to a definite bulk 148 ROBINSON AND BRISCOE : The silver content of this solution and of the main washings was then determined by nephelometric comparison of aliquot portions with standard silver solutions and the weight of silver 'lost thus ascertained was deducted from the weight of silver originally taken.Statement and Discussion of Results. Several preliminary analyses made on the middle fraction of ammonium bromide No.57 whilst useful in establishing the methods are not comparable in value with those of the final series : hence the results are omitted here. The final series consisted of eight determinations four on the ammonium bromide from the head fraction No. 71 and four on t,hat from the tail fraction No. 43. The essenthl data are given in Table I. TABLE I. Scries I . 1 71 A 3.69325 2 , , 5.06115 3 , , 3-93515 4 ? , 3.67332 Serie.9 I I . 5 43 A 5-14730 6 ,? 3.08140 7 , B 3.34631 S , , 3.43817 0.00058 3-69267 6.42874 0-00297 5.05818 8.80494 0.00374 3.93141 6.84337 0.00097 3.67235 6.39249 Mean of Series I. 0.00146 5-14584 8.95708 0.00111 3.08029 5-36261 0-00072 3.34559 5.82369 0.00251 3-43566 5.98102 Mean of Series 11. General mean 0,574400 79-933 0.574471 79.910 0.574484 79.906 0.574479 79.908 0.574459 79.914 0.574499 79.901 0.574401 79-933 0.574479 79.907 0.574427 79.916 0.574451 79.914 0.574455 79.914 +0.019 - 0.004 -0.00s -0.006 & 0.009 -0.013 + 0.01 7 - 0.009 + 0-002 fO.011 &0.010 In the first group of analyses the extreme variation in the ratio Ag AgBr is 0.000084 or 1 part in 6840 that in the atomic weight of bromine is 0.027 or 1 part in 2990.In the second group t.he cor-responding variations are 0-000096 or 1 part in 5984 and 0.032 or 1 part in 2493. The magnitude and sign of these variations indicate that the mean value of the atomic weight deduced from each series has an error probably less than 0.01 or in round numbers, about 1 part in 8000.The mean atomic weights from the two series differ by but 1 part in 40,000 as a change of lye in the isotope ratio would change the atomic weight by 0.02 and should have been appreciable in these determinations it appears that a fractionation of ammonium bromide involving 2700 crystallisations does not produce such a change. This result affording as it does more precise confirmation of th A REDETERMINATION OF THE ATOMIC WEIGHT OF BROMINE. 149 conclusion drawn by Richards and Hall is of some theoretical interest. It is in particular instructive to institute a comparison between t'he present results and those recorded for salts of kindred rare-earths where the solubility differences are of the same order. The solubilities of the hexahydrated nitrates of lanthanum and neodymium La(NB,),,6H20 and Nd(N0,),,6H20 are respect-ively 151.1 and 152.9 parts of anhydrous nitrate in 100 parts of water (James and Whittemore J .Amer. Chem. Xoc. 1912 34, 1168; James and Robinson ibid. 1913,35 754). As the molecular weights are 324.8 (La = 138-8) and 330-2 (Nd = 144.2) the mole-cular solubilities are 0,46520 and 0.46515. The coincidence of these numbers within one part in 9000 is obviously accidental but the molecular solubilities evidently differ by no more than the error of the solubility determinations say 2 or 3 parts in 1000 parts. The effect of fractional crystallisation in this case is shown in t'he investigations inter alios of Demargay (Cmpt. rend. 1896 122, 728; 1900 130 1021) and of Baxter and Chapin ( J .Amer. Chem. Soc. 1911 33 1). In the latter case for example about 1600 crystallisations as double ammonium nitrates and aboutl 1300 as simple nitrates produced a number of fractions of neodymium free from appreciable traces of other earths. The fact that 2000 crystallisations or fewer completely separate these earths whilst more than 2500 crystallisations do not appreci-ably change the proportions of the two kinds of molecule in ammon-ium bromide may be explained by and therefore affords chemical evidence supporting the theories of Bohr and of Bury (J. Amer. Chem. Xoc. 1921 43 1602) whereby the additional electrons in the atom of the heavier of a pair of rare-earth metals are supposed to be less intimately associated with the corresponding protons than are the additional electrons in the heavier of a pair of isotopes.Regarding the data as one series of determinations of the atomic weight of bromine it is to be noted that the extreme variation in the ratio Ag AgBr is from 0-574400 to 0.574498 or 1 part in 5745, whilst that in the atomic weight is from 79.901 to 79-933 or 1 part in 2500. The general mean values are given in Table I. A discussion of all the available data for the ratio of silver to silver bromide both direct and indirect has been given by Clarke (" A Recalculation of the Atomic Weights," 4th Edition Mem. Nnt. Acud. Sci. 1920 16 71) and need not be attempted here. The best direct determinations are those of Baxter (J. Amer. Chem. Soc., 1906 28 1322) whose general mean of 18 determinations of the ratio Ag AgBr is 0-57445 a figure substantially identical with that calculated by Clarke as the general mean of all determinations.Possible sources of error in the present determinations are 150 BRISCOE ROBINSON AND STEPHENSON : (1) errors in weighing ; (2) loss of silver in transference ; (3) impurity in the silver; (4) loss of silver bromide mechanically or in solution; (5) the presence of chlorine or iodine in the ammonium bromide. The error in weighing was undoubtedly too small to have any signifi-cant effect and the mode of transference of silver solution to the precipitation flask would appear to eliminate any risk of mechanical loss. The methods used for the preparation of pure silver have been shown to yield a metal containing less than 1 part of impurity in 300,000 parts of silver (Briscoe and Little J. 1914 105 1320). There can be little doubt that the chief error in the determination of weight lay in the nephelometric estimation of the silver lost (4) in washings and retained by the flask and filter a careful review of the analytical details leads to the conclusion that this error was not greater than 0.0001 g. but it was probably the one really significant error in the determinatioiis. With regard to the purity of the bromine it is certain that in such a prolonged fractionation the whole of any chlorine and iodine originally present would have become concentrated in opposite end fractions therefore the identity of the results obtained with these fractions shows that the chemical purification subsequent to fractionation had so far reduced the proportion of these halogens that their effect on the atomic weight of bromine was inappreciable. The final mean value of the ratio Ag AgBr now found differs from Baxter’s value by less than 1 part in 100,000 and the rounded mean value of the atomic weight Br = 79.92 with a probable error & 0.0031 confirms the accepted atomic weight. UNIVERSITY OF DURHAM ARMSTRONG COLLEGE, NEWCASTLE UPON TYNE. [Received November 3rd 1924.

ISSN:0368-1645    

DOI:10.1039/CT9252700138

出版商:RSC    

年代:1925

数据来源: RSC

摘要:

150 BRISCOE ROBINSON AND STEPHENSON : XX1V.-The Use of Fused Borax i n the Determination of the Atomic Weight of Boron. By HENRY VINCENT AIRD BRISCOE PERCY LUCOCK ROBINSON, and GEORGE EDWARD STEPITENSON. THOUUH a few determinations of the atomic weight of boron have been made by ascertaining the ratio of boron halides to silver, the majority have depended in one way or another upon weighing anhydrous borax in the form of borax-glass. A detailed discussion of the results may be found in Clarke’s “ A Recalculation of the Atomic Weights ” (Hem. Nat. Acad. Sci. 1920 16 205) and it is sufficient here to give a list of the determinations. Table I records all the previous data classified according to the nature of the method employed the wide divergence among the results render THE USE OF FUSED BORAX W THE DETERMINATION ETC.161 the “probable errors” obviously valueless as a measure of the weight to be given to each determination and they are therefore, omitted. TABLE I. Previous Determiirzations of the Atomic Weight of Boron. A. Determinations dependent upon weighing fused borax : Estimation of water in borax. 11.023 10-859 1869. DobrovoEsky. Estinmtion of water in bomx. 1st series. 2nd serk. 11.529 1892. Hoskyns- Abrahall. Decahydrate to borax glass. 10.703 1893. Ramsay and Aston. Decahydrate to borax glass. 10.946 10.955 11.059 1898. Armitage. Decahydrate to borax glass. 10,986 uric acid. 10.933 1918. Smith and van Haagen. Borax glass to sodium sulphate. 10.904 10.903 10.905 10.899 10-901 :z :::27} Borax glass to sodium chloride.Borax glass to silver chloride. Borax glass titrated with sulph-Borax glass to sodium fluoride. Borax glass to sodium carbonate. Borax glass to sodium nitrate. Borax glass to sodium chloride. Mean of all determinations. 10.964 Mean excluding the first four results.. 10.939 B. Determinations of the ratio of a boron halide to silver or silver halide : 1899. Gautier. BBr 3AgBr. 11.016 BC‘I 3AgCl. 10.947 1922. Hiinigschmid and BCl 3AgCI. 10.840 Birkenbach. 10.818 10,825 1892. Hoskyns-Abrahall. BBr 3Ag. 10-880 Mean excluding Gautier’s results. 10.827 ~ C. Determinations of ratios which do not involve fused borax or a boron 1893. Rimbach. Na2B40,10H20 hydrochloric acid solution. 11.006 1899. Gautier. B2S 3BaS0,.11.024 B,C 6C0,. 10.997 1923. Stock and Kuss. B,Hs 6H,. 10.806 halide : References Berzeliw Pogg. Ann. 1826 8 1 ; Laurent J . pr. Chem., 1849 47 415; Dobrovolsky Doctoral Disaertatwn Kiev 1869; Hoskyns-Abrahall J. 1892 61 650; Ramsay and Aston J. 1893 68 211; Armitage, P. 1898 14 22; Smith and van Haagen Carnegie Inst. Washington Pub-lication No. 267 1918; Gautier Ann. Chim. Phy8. 1899 [vii] 18 352; Hdnigschmid and Birkenbach Ber. 1923 56 [B] 1467; Rimbach Bcr., 1893 26 164; Stock and Kuss Ber. 1923 56 [B] 314; 8. anorg. Chem., 1923,128 49. Certain of these determinations (printed in italics) are unsatis-factory. In Group A those of Bemelius and Laurent have no pretensions to great accuracy Dobrovolsky’s two series are s 152 BRISCOE ROBINSON AND STEPHENSON : gravely discordant as to be valueless; and Abrahall’s results are definitely those of preliminary analyses thus these may be excluded making the mean result for the Group B = 10.939.I n Group B Gautier’s results show discordance so grave and so unaccountable in a halide ratio as to necessitate their immediate exclusion the remaining results give the mean value B = 10.827. I n Group C Gautier’s determinations involve eccentric ratios apparently unsuitable for atomic weight determination. The two remaining values may be retained but are not pertinent to the point now to be discussed. Reviewing all the results in Groups A and B not excluded for the reasons given it is immediately obvious that those dependent upon fused borax have a general tendency to be higher by about 0.1 than those deduced from halide ratios.As experience has shown that the halide ratios mually afford a very trustworthy means of determining atomic weights and as moreover determinations in this laboratory which will form the subject of another com-munication confirmed the general result thereby attained we were led to suspect that in the use of borax there lay some hitherto unsuspected source of systematic error. The present determinations were therefore undertaken with a two-fold object first to obtain independent confirmation of the values for the atomic weight of boron obtained by earlier workers by the analysis of borax; and secondly to attempt to ascertain whether the fractional crystallisation of boric acid from aqueous solution produces any change in the isotope ratio of boron.As, for reasons which mill appear in due course the results give no information on the second point and as the general nature of such an enquiry has been discussed elsewhere (Robinson and Briscoe, preceding paper) this secondary object need but be mentioned here in explanation of the nature of the boric acid used as starting material . Outline of the Method. Of the possible means of analysing borax its titration with aqueous hydrochloric acid was chosen because the experimental procedure is relatively simple and therefore little liable to error, and because borax can thus be referred directly to silver chloride, for which the antecedent atomic weights are well known. Rimbach (Zoc. cit.) in his work upon the titration of borax decahydrate has shown that the reaction proceeds qua’ntitatively according to the equation : Na,B,O + 2HC1+ 5H,O + 2NaC1+ 4H3B03.Preliminary tests described later showed that the end-point coul THE USE OF FUSED BORAX IN THE DETERMINATIOK ETC. 153 be observed with an accuracy sufficient for our purpose and the work of Smith and van Haagen afforded the strongest evidence that fused borax was a definite compound well suited to precise work. Borax prepared from boric acid and pure sodium carbonate, was purified by fractional crystallisation with centrifugal drainage of the crystals and the borax decahydra,te obtained was fused in platinum vessels in an electrically heated muffle furnace in a current of dry air free from carbon dioxide.The resultant borax glass was weighed dissolved in water and titrated with NI5-hydro-chloric acid solution delivered from a weight burette ; the titration being completed by the addition of A7/100-acid solution from an accurately calibrated burette using methyl-red as indicator. The acid was standardised by taking a weighed quantity and pre-cipitating the whole of the chlorine as silver chloride which was collected dried and weighed. Hence the ratio actually determined wits Na,B,O 2AgC1. Therefore the following method was adopted : The Determination of Weight. All weighings of borax and silver chloride were made on the special Oertling balance sensitive to 0-01 mg. or less already described (Robinson and Briscoe Zoc. cit.) with weights carefully calibrated for relative weight in air and all usual precautions.Fused borax was weighed directly on the balance pan silver chloride was weighed in the tared bottle used to collect the precipitate. The standard acid solution was weighed in a stoppered burette, using another similar burette as tare on a standard No. 7 S.W. Oert-ling balance ca,rrying a load of 300 g. in each pan and sensitive to 0.1 mg. A second set of calibrated weights was used in this case. As the standard solution only served as a means of referring borax to silver chloride the relation of the second set of weights to the first is immaterial. The relative vacuum weights of borax and silver are given to the nearest 0.01 mg. those of standard acid to the nearest 0-5 mg. The vacuum corrections applied were calculated using the densities : silver chloride D = 5.50 ; borax D = 2.357 (Smith and van Haagen, Preparation of Reagents.The water and nitric acid were prepared by the methods described in a recent communication (Robinson and Briscoe Zoc. cit.) and the silver used was a part of the stock prepared for the work there described. Hydrochloric Acid.-About 3 litres of pure reagent acid main-zoc. cit.) 154 BRISCOE ROBINSON AND STEPHENSON : tained at boiling point in a glass flask were treated for 30 minutes with a rapid current of chlorine gas from a cylinder of liquid chlorine and the excess of chlorine was then boiled off. Thus any traces of bromine and iodine were removed. The acid then stood over-night with copper foil previously cleaned with nitric acid and distilled water to remove arsenic.FIG. 1. FIG. 2. Next day the acid was transferred to a resistance glass still fitted with a ground-in condenser heated for 15 minutes to cause a vigorous evolution of hydrogen chloride gas and thus to eliminate any remaining volatile impurity and finally diluted to a density of 1-10 and twice distilled considerable head and tail fractions being rejected in each distillation. The main fraction from the second distillation was used forthwith for the preparation of the standard acid. The approximate strength of the acid having been determined by diluting a weighed portion and titrating it agains THE USE O F FUSED BORAX IN THE DETERMINATION ETC. 155 fused borax the requisite volume of the acid was transferred to the storage bot,tle and diluted to 4000 C.C.with pure water. In order to ensure as far as possible that the concentration of the standard acid should remain constant during the series of titrations the storage bottle was fitted with a well-ground glass stopper of the form shown in Pig. 1 where A is a stopcock and capillary tube for delivery of acid and B is a second tube passing to the bottom of the bottle and also fitted with a stopcock to admit air when the hottle being inverted acid was withdrawn. Before each withdrawal of acid the contents of the bottle mere mixed by vigorous shaking and in order to minimise the volume of acid withheld from this agitation the tube B was made of capillary bore. This stopper was wired in place and was not removed during the whole series of standardisations and analyses.Before use, the bottle had been wdl cleaned and rinsed allowed’ to stand for some weelis full of approximately S /5-hydrochloric acid and then again well washed with water. A quantity of approximately N/IBO-acid was prepared by diluting in a calibrated flask a weighed quantity of the standard AT/5-acid : thus it was possible by use of an appropriate factor to convert the volume of K/lOO-acid used in each titration to the corresponding weight of N/5-acid which was added to the weight determined in the weight burette. I n the standardisation of the AV/5-acid a weighed quantity was delivered into a slight excess of aqueous silver nitrate prepared from pure silver and nitric acid. and the precipitated silver chloride mas collected washed and weighed by the method already de-scribed (Robinson and Briscoe Zoc.cit.). In this case of course, the chloride found nephelometrically in the washings and ammoniacal rinsings was calculated to silver chloride and added to the observed weight. The essential data of the standardisations are given in Table 11. TABLE 11. I. 11. Vacuum %-eight of acid taken ............... 154.4826 g. 160.9230 g. Vacuum weight of silver chloride ............ 4.52544 g. 4.71377 g. Ratio silver chloride hydrochloric acid ... 0.0029294 0.0020292 Mean value of ratio .............................. 0.0029293 All flasks and burettes used here and in the titrations were carefully calibrated by weighing out with water in the usual way. E’ractional Crystallisat ion of Eoric Acid.About 14 kilos of commercial boric acid supplied by Messrs. Borax Consolidated Ltd but oE unknown origin were fractionall 156 BRISCOE ROBINSON AND STEPHENSON : crystallised (about 70 crystallisations) until two series A and B, each of 19 fractions were obtained. Each fraction contained about 350 g. of boric acid dissolved in 1500 C.C. of water. The fractions were contained in 2-litre round Jena flasks fitted with loose glass stoppers to exclude dust crystallisation was effected by slowly heating the whole set of flasks to boiling on a large hot plate and allowing them to cool over-night. The liquor was removed from each flask by pouring off through a filter of copper gauze which retained all h e crystals then the filter was reversed and liquor from the flask next in the series was poured in through the filter thus rinsing the fine crystals back into the flask from which %hey had come.In this way beginning with the head (most soluble) fraction all the liquors were moved up one place at each crystallisation and distilled water was added to the tail fraction. After several (usually three or four) crystallisafions the fail fraction disappeared and the head liquors were evaporated to form a new head fraction. Eoth series were systematically recrys-tallised after this fashion and by careful mana,gement the fractions were kept reasonably constant in size and number. After the 60th crystallisation of both series about 1150 crystal-lisations in all. having been made in each the extreme head and tail fractions were rejected and the heads A30 and B30 the tails A14 and B15 and the middle fractions A23 and E24 were taken for conversion into borax.Preparation and Purification of Borax. In order to obtain strictly comparable samples of borax the operations here described were carried out simultaneously on all six samples of boric acid. About 120 g. of boric acid were added gradually to a slight excess (about 0.5%) over the calculated equivalent of pure sodium carbonate dissolved in about 200 C.C. of hot water. The sodium carbonate originally very pure had been twice recrystallised from water and was spectroscopically free from potassium. The solution was boiled to remove carbon dioxide filtered whilst hot and allowed to cool slowly without movement until about one-tenth of the borax had crystallised out.Then the clear liquor was poured off quickly into another vessel and further cooled with agitation, yielding a main crop of fine crystals of borax decahydrate which were filtered with suction and immediately transferred to ghss tubes for centrifugal drainage. The drainage tubes had in the bottom a thick pad of dry cotton wool covered with a wad of small filter papers and a porcelain disk they were filled with the damp salt closed by corks covered with filter paper and centrifuged fo THE USE OB FUSED BOUX IN THE DETERMINATION ETC. 157 10 minutes a t a speed of 2500 revolutions per minute. Thus the mother-liquor was very effectively removed. The salt contained in a platinum dish was first dehydrated in an electrically-heated silica muffle kept a t 200-300' until intumes-cence ceased and then fused by raising the temperature to about 700-800".It thus formed a perfectly clear glass having only a faint blue tinge due to copper derived from the wire gauze filter mentioned above. Some difficulty was experienced at first in dis-solving the borax glass in water later it was found that if the dish containing the fused glass were floated on cold water the mass developed numerous cracks which allowed water to penetrate the glass and greatly hastened solution. To dissolve the glass, the dish containing it was wholly immersed in water in a covered Durosil beaker heated over a Rose burner solution was usually complete in about 2 hours. After fusion the borax was recrystallised four times from water in the manner already described with centrifugal drainage of the main crop a t each stage.Thus each sample was recrystallised five times in all about one-tenth of the material in the head frac-tion and the same amount in the tail fraction being rejected each time. The crystallisations were done in covered Erlenmeyer flasks of Durosil both these and the beakers having been thoroughly cleaned and boiled out with water for several days before use. Tests for the chief impurities carried out on the mother-liquors (head fraction) from each crystallisation in which the impurities present tended to concentrate gave a valuable indication of the purity of the main fraction without sacrifice of material therefrom. Copper was estimated colorimetrically in an ammoniacal solution containing 1 g.of borax decahydrate; the standard solution of copper sulphate contained 1 part of copper in 100,000 parts and in each case a " blank " test was made on the reagents alone. The head fractions from the earlier crystallisations contained traces of copper but those from the final crystallisafion of all six samples were absolutely free from copper. Phosphctte.-Mofher-liquor equivalent to 1 g. of borax deca-hydrate was treated hot with nitric acid ammonium nitrate and ammonium molybdate. No trace of yellow ammonium phospho-molybdate was observed at any stage of the purification. SuZphte.-The solution of borax was acidified with hydrochloric acid treated with barium chloride solution boiled and kept, covered over-night.The mother-liquor from the third recrystal-lisations showed traces of sulphate but tests 011 the crystals gave negative results. Two further recrystallisations were made on eac 158 BRISCOE ROBINSON AND STEPHENSON : sample and the mother-liquors from these gave negative results on the sulphate tests. Chloride.-Nitric acid and silver nitrate were added to a solution containing 1 g. of crystallised borax. The third recrystallisation showed a slight opalescence; later tests mere negative, The final main fractions of borax were partly dehydrated by standing for 3 weeks over solid potassium hydroxide in desiccators and were then stored in stoppered bottles capped to exclude dust. Fusion of the pure borax was carried out in a platinum dish in the electrically heated muffle in a current of air free from carbon dioxide and dried over solid caustic potash.The weight of borax taken was such as to yield from 3-10 g. of resultant " glass," as required and the dehydration and fusion were conducted in the manner described above. When a clear glass was obtained usually after about 1-14 hours' fusion a further period in no case less than 2 hours was allowed for complete dehydration. A shallow dish was used for fusion and thus a large surface of borax was exposed. Samples of the molten glass were taken in two ways : (i) by pouring small beads on to a clean cold platinum surface; (ii) by dipping the bottom of a clean platinum crucible into the melt. In the latter case the glass adhered whilst hot but on cooling cracked off in pieces weighing about 0.3 g.The samples were immediately transferred to and kept in it desiccator con-taining solid caustic potash. As tests showed that when a bead of the glass weighing about 2 g. mas kept on the balance pan for 3 days its weight did not change appreciably this method of storage was evidently satis-factory. In every case the glass was weighed within 2 days after its fusion. Method of Analysis. Preliminary tests with a number of indicators showed that under the conditions of the titration methyl-red gave much the sharpest colour change especially when the end-point chosen was slightly on the acid side. Under these conditions in N/lO-borax solution 2-3 drops of A7/100-acid or alkali gave a considerable and sharp colour change.During further tests which showed that the end-point in the borax titration was unaffected by moderate additions of boric acid and sodium chloride it was observed that in a solution made from boric acid and salt in the concentration which would be produced in the titration the end-point was quite indefinite. This curious fact had no direct significance in the analyses now reported but its further investigation at a future time is proposed. The titrations were made by two dist'inct methods described below THE USE OF FUSED BORSX I N THE DETERMINATION ETC. 159 (a) Using the weight burette. Weighed beads of borax glass were dissolved to a 2% solution in water by boiling in a covered flask. After cooling a quantity of NlSacid calculated to be 990/ of that required for complete neutralisation was added from the weight burette a fixed volume of a stock solution of methyl-red was pipetted in and the titratioii was completed by adding N/lOO-acid from a burette.The quantity of the latter required to give a match with a standard of definite pink shade could be ascertained with certainty within 0.1 C.C. Afterwards a measured excess of N/100-acid was added then a measured excess of an equivalent solution of borax sufficient to make the solution distinctly yellow and the end-point was again determined with X/lOO-acid. (b) B y direct zueighingr of the acid soluliorb. As several of the earlier determinations showed unaccountable discrepancies which might have been due to loss of borax (by spurting during solution) or of acid (by splashing when pouring in from the weight burette), a method of titration was devised to eliminate the possibility of such errors.The apparatus shown in Fig. 2 consisted of a 200 C.C. conical flask A and a reflux condenser 13 with a spray-trap C, connected to A by a carefully ground joint. TABLE 111. Data of Titratiom of Borax Glass. Sample number. A14 1 2 3 3a 4 5 6 A24 1 2 3 4 5 6 A30 1 2 3 4 5 6 7 8 9 10 Vacuum wt. borax glass. 1.99413 1.97982 1.93077 0.81470 1.01079 1-04G41 1-03879 1.00759 1.01246 2.14923 1.84391 1.90780 1.95540 1.21340 1.46470 1.41400 1.31097 0.67774 0.90300 1.01566 1 -122 62 1.22427 1.46529 (g.) of Vacuum mt. N / 5 -acid. 96.G881 05.9G36 93.5412 39-4923 48.9751 50.6956 50.3263 48.82 5 8 49.1306 104.1576 89.3821 92.4578 94.73 15 58.8361 70.981 2 68.5272 63.5162 32.8309 43.6951 49-1406 54.2960 59.2639 70.92U1 k.) of Calculated vacuum mt.silver chloride. 2.83229 2.81 107 2.7401 1 1.1 5655 1.43463 1.48303 1.47431 1.43026 1.43919 3.05110 2.G1828 3.70838 2.77498 1.72349 2.07926 2.00737 1.86059 0.96172 1.28005 1.43948 1.59060 1.73603 2.07747 (g.1 of Ratio : borax glass silver chloride' 0.704068 0.704294 0-704632 0-704239 0.704564 0- 70463 8 0-704640 0.704481 0.703494 0.704412 0.704245 0.704407 0-704686 0.70403 G 0.704434 0.704403 0.704600 0.704717 0.705439 0.706574 0-705829 0.705215 0.705324 Atomic weight .10.961 10.977 11.001 10.973 10.996 11.002 11.002 10.990 10.920 10-985 10.974 10.985 11-005 10.958 10.987 10.985 10.999 11-007 11.059 11.069 11-087 11.043 11.05 16Q BRISCOE ROBINSON AND STEPHENSON : This apparatus was made in duplicate of Durosil glass and was cleaned with all the precautions already described. In using it, the required amount of N/5-acid was weighed in A against another similar flask as tare the weighed borax was carefully slid down the dry side of the flask into the acid the condenser was fitted a little pure water was introduced into the spray trap and the flask was heated gently over a Rose burner until the borax had completely dissolved (about 1 hour).After cooling the contents of the bulbs and condenser were rinsed into the flask these were removed and the titration was completed with N/lOO-acid as described above. Working in this manner the total volume of the solution titrated was little greater than that of the NIS-acid used. Statement a.nd Disczmion of Reszdts. Table 111 gives the essential data of all the analyses made and the values of the atomic weight of boron calculated therefrom. The results are evidently subject to errors (1) in the weight of borax taken (2) in the volume of N/lOO-acid used (3) in the weight of N/5-acid used in the titration and (4) in the standardisation of the iV/6-acid the probable magnitude and effect of these errors are shown in Table IV. TABLE Iv. Corresponding variation in the atomic weight of boron.-J= 0.005 f 0.001 & 0.001 3 0-004 Total maximum error ........................... f0-011 Making all due allowance for these errors it would appear that the value obtained in each titration for the atomic weight of boron should not be in error by more than one or two units in the second decimal place and there remain among the data considerable differ-ences which must be otherwise explained. After much worry had been caused by unaccountable and erratic variations in the atomic weight it became apparent as data accumulated that the result was in many cases EL function of the duration of fusion of the borax. Fortunately precise records of the fusions were available and their correlation with the results is shown in Table V.It is clear that a high atomic weight iq always associated with a long period of fusion. The additional results on A30 Nos. 7 8 9 and 10 confirm this in a striking way. The most probable inference is clear a higher atomic weight corresponds with a lesser amount of acid used to neutralise a given weight of borax hence to a lesser content of soda (Na,O) in that Probable maximum value of error. (1) 0.1 C.C. of N/lOO-acid on 1 g. of borax-glass ...... (2) 0.02 Mg. on 1 g. of borax .............................. (3) 0-5 Mg. on 50 g. of N/5-acid ........................ (4) Difference between standardisations 1 in 15,000 THE USE OF FUSED BORAX IN THE DETERMXNATIOS ETC. 161 Sample N O . A14 1 2 3 3-4 4 5 6 A24 1 r) r* 3 4 5 6 A30 1 2 3 4 5 6 7 8 9 10 TABLE V.Notes on Treatment oJ- Samples. Atomic weight. 10.961 10.977 11401 1 10.973) 10.996 11.002 11.002 10.990 1 10.920) ;;::::} 10.9851 10.974 I PO-958 10.987 10.985 10.999 11.0073\ Condition of fuaion of Method of analysis. borax g l m . Molten 4-5 hours. Extra 5 g. of crystals added to residue (1). Fused 34 hours. Both samples taken Extra crystals added to reei-due (2) ; fused 3 hours. Further amount of crystals minations by weight SimuItaneous deter-burette method. 9 ) dehydrated. Fused 62 hours. Simultaneous deter- 30 G. of crystals dehydrated minations by weight to fusion; kept molten burette method. 1 2 hours. Residue further fused 2 hours.Residue from 3 and 4 further 9 9 39 } fused 24 hours. 20 G. of crystals dehydrated s a m p 1 in g . and fused 6 hours before Weight burette used. =Yusik par- Residue from (1-5) fused for { 4houm. j 2 0 G. of crystals dehydrated Residue from 7 and 8 fused for i a further 7 hours. 9 9 and fused 10 hours. 11.043 \ Done by weight 11.051 J burette method. borax therefore on fusion borax loses soda and the extent of this loss increases with the duration of fusion. Molten borax glass is known t o volatilise but previous workers have differed as to whether any decomposition takes place. Walde-bott ( J . Amer. Chem. SOC. 1894,16 410) as a result of experiments on the fusion of borax was of the opinion that sodium tetraborate volatilised unchanged; he analysed the fused residue by treatment with ammonium fluoride and found no change in composition.The application of this method to an atomic weight determination w&s rejected however by Smith and van Haagen (Zoc. cit.). On the other hand Leonard (Chem. News 1598 77 104) in criticism of the determinabions of the atomic weight of boron by Armitage (Zoc. cit.) stated definitely that the residue obtained after fusion of borax required less standard acid for neutralisation than the original sample this corresponds with a loss of soda. Smith and van Haagen assumed that acidic gases from burners had affected Leonard’s borax but no such explanation can be advanced in thk case since an electrically heated furnace was used to fuse the borax. Their own samples of borax glass were fused to constant weight POT2.CSXVII. 162 CHALLENGER JINKS AND HASLAM THE SULPHUR in a long-necked platiiium flask and they concluded that the material condensed in the cooler part of the apparatus was identical in composition with the fused residue and was pure sodium tetra-borate. But their borax had been fused previously in an open crucible one may infer for about the same time in the case of all samples and the sample for analysis was taken from the upper portion of the main mass of glass which by rotation had been spread in a thin layer over the upper sides of the crucible and cooled quickly. Therefore the volatilisation of this sample in the flask without material change is quite consistent with its having already changed in Composition during the open fusion in the way now observed.Whatever the explanation may be it seems c1ea.r that the borax ratios are subject to grave uncertainty and the authors are definitely of opinion that all values for the atomic weight of boron determined by methods involving the weighing of fused borax should be entirely rejected in favour of those deduced from analyses of boron halides. In summarising the present results it seems proper to discard A24 No. 2 for unaccountable discordance and A30 Nos. 6 7 8 9, and 10 because in these cases the fusion was deliberately pro-longed. The mean atomic weight deduced from the remaining determinations B = 10.99 is in general agreement with the results previously obtained with fused borax and is close to the results of Ramsay and Aston for the ratio Na,B40,/2AgCl but differs widely from the results of determinations of the halide ratios.For reasons which have been made clear the authors attach no weight to this result. One of the authors (G. E. S.) desires to acknowledge a grant from the Department of Scientific and Industrial Research enabling him to take part in this investigation. UNIXERSITY OF DURHAM ARMSTRONG COLLEGE, NEWCASTLE-UPON -TPNE. [Received N m e m b e r 20th 1924. 150 BRISCOE ROBINSON AND STEPHENSON : XX1V.-The Use of Fused Borax i n the Determination of the Atomic Weight of Boron. By HENRY VINCENT AIRD BRISCOE PERCY LUCOCK ROBINSON, and GEORGE EDWARD STEPITENSON. THOUUH a few determinations of the atomic weight of boron have been made by ascertaining the ratio of boron halides to silver, the majority have depended in one way or another upon weighing anhydrous borax in the form of borax-glass.A detailed discussion of the results may be found in Clarke’s “ A Recalculation of the Atomic Weights ” (Hem. Nat. Acad. Sci. 1920 16 205) and it is sufficient here to give a list of the determinations. Table I records all the previous data classified according to the nature of the method employed the wide divergence among the results render THE USE OF FUSED BORAX W THE DETERMINATION ETC. 161 the “probable errors” obviously valueless as a measure of the weight to be given to each determination and they are therefore, omitted. TABLE I. Previous Determiirzations of the Atomic Weight of Boron. A. Determinations dependent upon weighing fused borax : Estimation of water in borax.11.023 10-859 1869. DobrovoEsky. Estinmtion of water in bomx. 1st series. 2nd serk. 11.529 1892. Hoskyns- Abrahall. Decahydrate to borax glass. 10.703 1893. Ramsay and Aston. Decahydrate to borax glass. 10.946 10.955 11.059 1898. Armitage. Decahydrate to borax glass. 10,986 uric acid. 10.933 1918. Smith and van Haagen. Borax glass to sodium sulphate. 10.904 10.903 10.905 10.899 10-901 :z :::27} Borax glass to sodium chloride. Borax glass to silver chloride. Borax glass titrated with sulph-Borax glass to sodium fluoride. Borax glass to sodium carbonate. Borax glass to sodium nitrate. Borax glass to sodium chloride. Mean of all determinations. 10.964 Mean excluding the first four results..10.939 B. Determinations of the ratio of a boron halide to silver or silver halide : 1899. Gautier. BBr 3AgBr. 11.016 BC‘I 3AgCl. 10.947 1922. Hiinigschmid and BCl 3AgCI. 10.840 Birkenbach. 10.818 10,825 1892. Hoskyns-Abrahall. BBr 3Ag. 10-880 Mean excluding Gautier’s results. 10.827 ~ C. Determinations of ratios which do not involve fused borax or a boron 1893. Rimbach. Na2B40,10H20 hydrochloric acid solution. 11.006 1899. Gautier. B2S 3BaS0,. 11.024 B,C 6C0,. 10.997 1923. Stock and Kuss. B,Hs 6H,. 10.806 halide : References Berzeliw Pogg. Ann. 1826 8 1 ; Laurent J . pr. Chem., 1849 47 415; Dobrovolsky Doctoral Disaertatwn Kiev 1869; Hoskyns-Abrahall J. 1892 61 650; Ramsay and Aston J. 1893 68 211; Armitage, P. 1898 14 22; Smith and van Haagen Carnegie Inst.Washington Pub-lication No. 267 1918; Gautier Ann. Chim. Phy8. 1899 [vii] 18 352; Hdnigschmid and Birkenbach Ber. 1923 56 [B] 1467; Rimbach Bcr., 1893 26 164; Stock and Kuss Ber. 1923 56 [B] 314; 8. anorg. Chem., 1923,128 49. Certain of these determinations (printed in italics) are unsatis-factory. In Group A those of Bemelius and Laurent have no pretensions to great accuracy Dobrovolsky’s two series are s 152 BRISCOE ROBINSON AND STEPHENSON : gravely discordant as to be valueless; and Abrahall’s results are definitely those of preliminary analyses thus these may be excluded making the mean result for the Group B = 10.939. I n Group B Gautier’s results show discordance so grave and so unaccountable in a halide ratio as to necessitate their immediate exclusion the remaining results give the mean value B = 10.827.I n Group C Gautier’s determinations involve eccentric ratios apparently unsuitable for atomic weight determination. The two remaining values may be retained but are not pertinent to the point now to be discussed. Reviewing all the results in Groups A and B not excluded for the reasons given it is immediately obvious that those dependent upon fused borax have a general tendency to be higher by about 0.1 than those deduced from halide ratios. As experience has shown that the halide ratios mually afford a very trustworthy means of determining atomic weights and as moreover determinations in this laboratory which will form the subject of another com-munication confirmed the general result thereby attained we were led to suspect that in the use of borax there lay some hitherto unsuspected source of systematic error.The present determinations were therefore undertaken with a two-fold object first to obtain independent confirmation of the values for the atomic weight of boron obtained by earlier workers by the analysis of borax; and secondly to attempt to ascertain whether the fractional crystallisation of boric acid from aqueous solution produces any change in the isotope ratio of boron. As, for reasons which mill appear in due course the results give no information on the second point and as the general nature of such an enquiry has been discussed elsewhere (Robinson and Briscoe, preceding paper) this secondary object need but be mentioned here in explanation of the nature of the boric acid used as starting material .Outline of the Method. Of the possible means of analysing borax its titration with aqueous hydrochloric acid was chosen because the experimental procedure is relatively simple and therefore little liable to error, and because borax can thus be referred directly to silver chloride, for which the antecedent atomic weights are well known. Rimbach (Zoc. cit.) in his work upon the titration of borax decahydrate has shown that the reaction proceeds qua’ntitatively according to the equation : Na,B,O + 2HC1+ 5H,O + 2NaC1+ 4H3B03. Preliminary tests described later showed that the end-point coul THE USE OF FUSED BORAX IN THE DETERMINATIOK ETC. 153 be observed with an accuracy sufficient for our purpose and the work of Smith and van Haagen afforded the strongest evidence that fused borax was a definite compound well suited to precise work.Borax prepared from boric acid and pure sodium carbonate, was purified by fractional crystallisation with centrifugal drainage of the crystals and the borax decahydra,te obtained was fused in platinum vessels in an electrically heated muffle furnace in a current of dry air free from carbon dioxide. The resultant borax glass was weighed dissolved in water and titrated with NI5-hydro-chloric acid solution delivered from a weight burette ; the titration being completed by the addition of A7/100-acid solution from an accurately calibrated burette using methyl-red as indicator. The acid was standardised by taking a weighed quantity and pre-cipitating the whole of the chlorine as silver chloride which was collected dried and weighed.Hence the ratio actually determined wits Na,B,O 2AgC1. Therefore the following method was adopted : The Determination of Weight. All weighings of borax and silver chloride were made on the special Oertling balance sensitive to 0-01 mg. or less already described (Robinson and Briscoe Zoc. cit.) with weights carefully calibrated for relative weight in air and all usual precautions. Fused borax was weighed directly on the balance pan silver chloride was weighed in the tared bottle used to collect the precipitate. The standard acid solution was weighed in a stoppered burette, using another similar burette as tare on a standard No.7 S.W. Oert-ling balance ca,rrying a load of 300 g. in each pan and sensitive to 0.1 mg. A second set of calibrated weights was used in this case. As the standard solution only served as a means of referring borax to silver chloride the relation of the second set of weights to the first is immaterial. The relative vacuum weights of borax and silver are given to the nearest 0.01 mg. those of standard acid to the nearest 0-5 mg. The vacuum corrections applied were calculated using the densities : silver chloride D = 5.50 ; borax D = 2.357 (Smith and van Haagen, Preparation of Reagents. The water and nitric acid were prepared by the methods described in a recent communication (Robinson and Briscoe Zoc. cit.) and the silver used was a part of the stock prepared for the work there described.Hydrochloric Acid.-About 3 litres of pure reagent acid main-zoc. cit.) 154 BRISCOE ROBINSON AND STEPHENSON : tained at boiling point in a glass flask were treated for 30 minutes with a rapid current of chlorine gas from a cylinder of liquid chlorine and the excess of chlorine was then boiled off. Thus any traces of bromine and iodine were removed. The acid then stood over-night with copper foil previously cleaned with nitric acid and distilled water to remove arsenic. FIG. 1. FIG. 2. Next day the acid was transferred to a resistance glass still fitted with a ground-in condenser heated for 15 minutes to cause a vigorous evolution of hydrogen chloride gas and thus to eliminate any remaining volatile impurity and finally diluted to a density of 1-10 and twice distilled considerable head and tail fractions being rejected in each distillation.The main fraction from the second distillation was used forthwith for the preparation of the standard acid. The approximate strength of the acid having been determined by diluting a weighed portion and titrating it agains THE USE O F FUSED BORAX IN THE DETERMINATION ETC. 155 fused borax the requisite volume of the acid was transferred to the storage bot,tle and diluted to 4000 C.C. with pure water. In order to ensure as far as possible that the concentration of the standard acid should remain constant during the series of titrations the storage bottle was fitted with a well-ground glass stopper of the form shown in Pig.1 where A is a stopcock and capillary tube for delivery of acid and B is a second tube passing to the bottom of the bottle and also fitted with a stopcock to admit air when the hottle being inverted acid was withdrawn. Before each withdrawal of acid the contents of the bottle mere mixed by vigorous shaking and in order to minimise the volume of acid withheld from this agitation the tube B was made of capillary bore. This stopper was wired in place and was not removed during the whole series of standardisations and analyses. Before use, the bottle had been wdl cleaned and rinsed allowed’ to stand for some weelis full of approximately S /5-hydrochloric acid and then again well washed with water. A quantity of approximately N/IBO-acid was prepared by diluting in a calibrated flask a weighed quantity of the standard AT/5-acid : thus it was possible by use of an appropriate factor to convert the volume of K/lOO-acid used in each titration to the corresponding weight of N/5-acid which was added to the weight determined in the weight burette.I n the standardisation of the AV/5-acid a weighed quantity was delivered into a slight excess of aqueous silver nitrate prepared from pure silver and nitric acid. and the precipitated silver chloride mas collected washed and weighed by the method already de-scribed (Robinson and Briscoe Zoc. cit.). In this case of course, the chloride found nephelometrically in the washings and ammoniacal rinsings was calculated to silver chloride and added to the observed weight. The essential data of the standardisations are given in Table 11.TABLE 11. I. 11. Vacuum %-eight of acid taken ............... 154.4826 g. 160.9230 g. Vacuum weight of silver chloride ............ 4.52544 g. 4.71377 g. Ratio silver chloride hydrochloric acid ... 0.0029294 0.0020292 Mean value of ratio .............................. 0.0029293 All flasks and burettes used here and in the titrations were carefully calibrated by weighing out with water in the usual way. E’ractional Crystallisat ion of Eoric Acid. About 14 kilos of commercial boric acid supplied by Messrs. Borax Consolidated Ltd but oE unknown origin were fractionall 156 BRISCOE ROBINSON AND STEPHENSON : crystallised (about 70 crystallisations) until two series A and B, each of 19 fractions were obtained.Each fraction contained about 350 g. of boric acid dissolved in 1500 C.C. of water. The fractions were contained in 2-litre round Jena flasks fitted with loose glass stoppers to exclude dust crystallisation was effected by slowly heating the whole set of flasks to boiling on a large hot plate and allowing them to cool over-night. The liquor was removed from each flask by pouring off through a filter of copper gauze which retained all h e crystals then the filter was reversed and liquor from the flask next in the series was poured in through the filter thus rinsing the fine crystals back into the flask from which %hey had come. In this way beginning with the head (most soluble) fraction all the liquors were moved up one place at each crystallisation and distilled water was added to the tail fraction.After several (usually three or four) crystallisafions the fail fraction disappeared and the head liquors were evaporated to form a new head fraction. Eoth series were systematically recrys-tallised after this fashion and by careful mana,gement the fractions were kept reasonably constant in size and number. After the 60th crystallisation of both series about 1150 crystal-lisations in all. having been made in each the extreme head and tail fractions were rejected and the heads A30 and B30 the tails A14 and B15 and the middle fractions A23 and E24 were taken for conversion into borax. Preparation and Purification of Borax. In order to obtain strictly comparable samples of borax the operations here described were carried out simultaneously on all six samples of boric acid.About 120 g. of boric acid were added gradually to a slight excess (about 0.5%) over the calculated equivalent of pure sodium carbonate dissolved in about 200 C.C. of hot water. The sodium carbonate originally very pure had been twice recrystallised from water and was spectroscopically free from potassium. The solution was boiled to remove carbon dioxide filtered whilst hot and allowed to cool slowly without movement until about one-tenth of the borax had crystallised out. Then the clear liquor was poured off quickly into another vessel and further cooled with agitation, yielding a main crop of fine crystals of borax decahydrate which were filtered with suction and immediately transferred to ghss tubes for centrifugal drainage.The drainage tubes had in the bottom a thick pad of dry cotton wool covered with a wad of small filter papers and a porcelain disk they were filled with the damp salt closed by corks covered with filter paper and centrifuged fo THE USE OB FUSED BOUX IN THE DETERMINATION ETC. 157 10 minutes a t a speed of 2500 revolutions per minute. Thus the mother-liquor was very effectively removed. The salt contained in a platinum dish was first dehydrated in an electrically-heated silica muffle kept a t 200-300' until intumes-cence ceased and then fused by raising the temperature to about 700-800". It thus formed a perfectly clear glass having only a faint blue tinge due to copper derived from the wire gauze filter mentioned above. Some difficulty was experienced at first in dis-solving the borax glass in water later it was found that if the dish containing the fused glass were floated on cold water the mass developed numerous cracks which allowed water to penetrate the glass and greatly hastened solution.To dissolve the glass, the dish containing it was wholly immersed in water in a covered Durosil beaker heated over a Rose burner solution was usually complete in about 2 hours. After fusion the borax was recrystallised four times from water in the manner already described with centrifugal drainage of the main crop a t each stage. Thus each sample was recrystallised five times in all about one-tenth of the material in the head frac-tion and the same amount in the tail fraction being rejected each time.The crystallisations were done in covered Erlenmeyer flasks of Durosil both these and the beakers having been thoroughly cleaned and boiled out with water for several days before use. Tests for the chief impurities carried out on the mother-liquors (head fraction) from each crystallisation in which the impurities present tended to concentrate gave a valuable indication of the purity of the main fraction without sacrifice of material therefrom. Copper was estimated colorimetrically in an ammoniacal solution containing 1 g. of borax decahydrate; the standard solution of copper sulphate contained 1 part of copper in 100,000 parts and in each case a " blank " test was made on the reagents alone. The head fractions from the earlier crystallisations contained traces of copper but those from the final crystallisafion of all six samples were absolutely free from copper.Phosphctte.-Mofher-liquor equivalent to 1 g. of borax deca-hydrate was treated hot with nitric acid ammonium nitrate and ammonium molybdate. No trace of yellow ammonium phospho-molybdate was observed at any stage of the purification. SuZphte.-The solution of borax was acidified with hydrochloric acid treated with barium chloride solution boiled and kept, covered over-night. The mother-liquor from the third recrystal-lisations showed traces of sulphate but tests 011 the crystals gave negative results. Two further recrystallisations were made on eac 158 BRISCOE ROBINSON AND STEPHENSON : sample and the mother-liquors from these gave negative results on the sulphate tests.Chloride.-Nitric acid and silver nitrate were added to a solution containing 1 g. of crystallised borax. The third recrystallisation showed a slight opalescence; later tests mere negative, The final main fractions of borax were partly dehydrated by standing for 3 weeks over solid potassium hydroxide in desiccators and were then stored in stoppered bottles capped to exclude dust. Fusion of the pure borax was carried out in a platinum dish in the electrically heated muffle in a current of air free from carbon dioxide and dried over solid caustic potash. The weight of borax taken was such as to yield from 3-10 g. of resultant " glass," as required and the dehydration and fusion were conducted in the manner described above. When a clear glass was obtained usually after about 1-14 hours' fusion a further period in no case less than 2 hours was allowed for complete dehydration.A shallow dish was used for fusion and thus a large surface of borax was exposed. Samples of the molten glass were taken in two ways : (i) by pouring small beads on to a clean cold platinum surface; (ii) by dipping the bottom of a clean platinum crucible into the melt. In the latter case the glass adhered whilst hot but on cooling cracked off in pieces weighing about 0.3 g. The samples were immediately transferred to and kept in it desiccator con-taining solid caustic potash. As tests showed that when a bead of the glass weighing about 2 g. mas kept on the balance pan for 3 days its weight did not change appreciably this method of storage was evidently satis-factory.In every case the glass was weighed within 2 days after its fusion. Method of Analysis. Preliminary tests with a number of indicators showed that under the conditions of the titration methyl-red gave much the sharpest colour change especially when the end-point chosen was slightly on the acid side. Under these conditions in N/lO-borax solution 2-3 drops of A7/100-acid or alkali gave a considerable and sharp colour change. During further tests which showed that the end-point in the borax titration was unaffected by moderate additions of boric acid and sodium chloride it was observed that in a solution made from boric acid and salt in the concentration which would be produced in the titration the end-point was quite indefinite.This curious fact had no direct significance in the analyses now reported but its further investigation at a future time is proposed. The titrations were made by two dist'inct methods described below THE USE OF FUSED BORSX I N THE DETERMINATION ETC. 159 (a) Using the weight burette. Weighed beads of borax glass were dissolved to a 2% solution in water by boiling in a covered flask. After cooling a quantity of NlSacid calculated to be 990/ of that required for complete neutralisation was added from the weight burette a fixed volume of a stock solution of methyl-red was pipetted in and the titratioii was completed by adding N/lOO-acid from a burette. The quantity of the latter required to give a match with a standard of definite pink shade could be ascertained with certainty within 0.1 C.C.Afterwards a measured excess of N/100-acid was added then a measured excess of an equivalent solution of borax sufficient to make the solution distinctly yellow and the end-point was again determined with X/lOO-acid. (b) B y direct zueighingr of the acid soluliorb. As several of the earlier determinations showed unaccountable discrepancies which might have been due to loss of borax (by spurting during solution) or of acid (by splashing when pouring in from the weight burette), a method of titration was devised to eliminate the possibility of such errors. The apparatus shown in Fig. 2 consisted of a 200 C.C. conical flask A and a reflux condenser 13 with a spray-trap C, connected to A by a carefully ground joint.TABLE 111. Data of Titratiom of Borax Glass. Sample number. A14 1 2 3 3a 4 5 6 A24 1 2 3 4 5 6 A30 1 2 3 4 5 6 7 8 9 10 Vacuum wt. borax glass. 1.99413 1.97982 1.93077 0.81470 1.01079 1-04G41 1-03879 1.00759 1.01246 2.14923 1.84391 1.90780 1.95540 1.21340 1.46470 1.41400 1.31097 0.67774 0.90300 1.01566 1 -122 62 1.22427 1.46529 (g.) of Vacuum mt. N / 5 -acid. 96.G881 05.9G36 93.5412 39-4923 48.9751 50.6956 50.3263 48.82 5 8 49.1306 104.1576 89.3821 92.4578 94.73 15 58.8361 70.981 2 68.5272 63.5162 32.8309 43.6951 49-1406 54.2960 59.2639 70.92U1 k.) of Calculated vacuum mt. silver chloride. 2.83229 2.81 107 2.7401 1 1.1 5655 1.43463 1.48303 1.47431 1.43026 1.43919 3.05110 2.G1828 3.70838 2.77498 1.72349 2.07926 2.00737 1.86059 0.96172 1.28005 1.43948 1.59060 1.73603 2.07747 (g.1 of Ratio : borax glass silver chloride' 0.704068 0.704294 0-704632 0-704239 0.704564 0- 70463 8 0-704640 0.704481 0.703494 0.704412 0.704245 0.704407 0-704686 0.70403 G 0.704434 0.704403 0.704600 0.704717 0.705439 0.706574 0-705829 0.705215 0.705324 Atomic weight .10.961 10.977 11.001 10.973 10.996 11.002 11.002 10.990 10.920 10-985 10.974 10.985 11-005 10.958 10.987 10.985 10.999 11-007 11.059 11.069 11-087 11.043 11.05 16Q BRISCOE ROBINSON AND STEPHENSON : This apparatus was made in duplicate of Durosil glass and was cleaned with all the precautions already described.In using it, the required amount of N/5-acid was weighed in A against another similar flask as tare the weighed borax was carefully slid down the dry side of the flask into the acid the condenser was fitted a little pure water was introduced into the spray trap and the flask was heated gently over a Rose burner until the borax had completely dissolved (about 1 hour). After cooling the contents of the bulbs and condenser were rinsed into the flask these were removed and the titration was completed with N/lOO-acid as described above. Working in this manner the total volume of the solution titrated was little greater than that of the NIS-acid used. Statement a.nd Disczmion of Reszdts.Table 111 gives the essential data of all the analyses made and the values of the atomic weight of boron calculated therefrom. The results are evidently subject to errors (1) in the weight of borax taken (2) in the volume of N/lOO-acid used (3) in the weight of N/5-acid used in the titration and (4) in the standardisation of the iV/6-acid the probable magnitude and effect of these errors are shown in Table IV. TABLE Iv. Corresponding variation in the atomic weight of boron. -J= 0.005 f 0.001 & 0.001 3 0-004 Total maximum error ........................... f0-011 Making all due allowance for these errors it would appear that the value obtained in each titration for the atomic weight of boron should not be in error by more than one or two units in the second decimal place and there remain among the data considerable differ-ences which must be otherwise explained.After much worry had been caused by unaccountable and erratic variations in the atomic weight it became apparent as data accumulated that the result was in many cases EL function of the duration of fusion of the borax. Fortunately precise records of the fusions were available and their correlation with the results is shown in Table V. It is clear that a high atomic weight iq always associated with a long period of fusion. The additional results on A30 Nos. 7 8 9 and 10 confirm this in a striking way. The most probable inference is clear a higher atomic weight corresponds with a lesser amount of acid used to neutralise a given weight of borax hence to a lesser content of soda (Na,O) in that Probable maximum value of error.(1) 0.1 C.C. of N/lOO-acid on 1 g. of borax-glass ...... (2) 0.02 Mg. on 1 g. of borax .............................. (3) 0-5 Mg. on 50 g. of N/5-acid ........................ (4) Difference between standardisations 1 in 15,000 THE USE OF FUSED BORAX IN THE DETERMXNATIOS ETC. 161 Sample N O . A14 1 2 3 3-4 4 5 6 A24 1 r) r* 3 4 5 6 A30 1 2 3 4 5 6 7 8 9 10 TABLE V. Notes on Treatment oJ- Samples. Atomic weight. 10.961 10.977 11401 1 10.973) 10.996 11.002 11.002 10.990 1 10.920) ;;::::} 10.9851 10.974 I PO-958 10.987 10.985 10.999 11.0073\ Condition of fuaion of Method of analysis.borax g l m . Molten 4-5 hours. Extra 5 g. of crystals added to residue (1). Fused 34 hours. Both samples taken Extra crystals added to reei-due (2) ; fused 3 hours. Further amount of crystals minations by weight SimuItaneous deter-burette method. 9 ) dehydrated. Fused 62 hours. Simultaneous deter- 30 G. of crystals dehydrated minations by weight to fusion; kept molten burette method. 1 2 hours. Residue further fused 2 hours. Residue from 3 and 4 further 9 9 39 } fused 24 hours. 20 G. of crystals dehydrated s a m p 1 in g . and fused 6 hours before Weight burette used. =Yusik par- Residue from (1-5) fused for { 4houm. j 2 0 G. of crystals dehydrated Residue from 7 and 8 fused for i a further 7 hours.9 9 and fused 10 hours. 11.043 \ Done by weight 11.051 J burette method. borax therefore on fusion borax loses soda and the extent of this loss increases with the duration of fusion. Molten borax glass is known t o volatilise but previous workers have differed as to whether any decomposition takes place. Walde-bott ( J . Amer. Chem. SOC. 1894,16 410) as a result of experiments on the fusion of borax was of the opinion that sodium tetraborate volatilised unchanged; he analysed the fused residue by treatment with ammonium fluoride and found no change in composition. The application of this method to an atomic weight determination w&s rejected however by Smith and van Haagen (Zoc. cit.). On the other hand Leonard (Chem. News 1598 77 104) in criticism of the determinabions of the atomic weight of boron by Armitage (Zoc.cit.) stated definitely that the residue obtained after fusion of borax required less standard acid for neutralisation than the original sample this corresponds with a loss of soda. Smith and van Haagen assumed that acidic gases from burners had affected Leonard’s borax but no such explanation can be advanced in thk case since an electrically heated furnace was used to fuse the borax. Their own samples of borax glass were fused to constant weight POT2. CSXVII. 162 CHALLENGER JINKS AND HASLAM THE SULPHUR in a long-necked platiiium flask and they concluded that the material condensed in the cooler part of the apparatus was identical in composition with the fused residue and was pure sodium tetra-borate. But their borax had been fused previously in an open crucible one may infer for about the same time in the case of all samples and the sample for analysis was taken from the upper portion of the main mass of glass which by rotation had been spread in a thin layer over the upper sides of the crucible and cooled quickly. Therefore the volatilisation of this sample in the flask without material change is quite consistent with its having already changed in Composition during the open fusion in the way now observed. Whatever the explanation may be it seems c1ea.r that the borax ratios are subject to grave uncertainty and the authors are definitely of opinion that all values for the atomic weight of boron determined by methods involving the weighing of fused borax should be entirely rejected in favour of those deduced from analyses of boron halides. In summarising the present results it seems proper to discard A24 No. 2 for unaccountable discordance and A30 Nos. 6 7 8 9, and 10 because in these cases the fusion was deliberately pro-longed. The mean atomic weight deduced from the remaining determinations B = 10.99 is in general agreement with the results previously obtained with fused borax and is close to the results of Ramsay and Aston for the ratio Na,B40,/2AgCl but differs widely from the results of determinations of the halide ratios. For reasons which have been made clear the authors attach no weight to this result. One of the authors (G. E. S.) desires to acknowledge a grant from the Department of Scientific and Industrial Research enabling him to take part in this investigation. UNIXERSITY OF DURHAM ARMSTRONG COLLEGE, NEWCASTLE-UPON -TPNE. [Received N m e m b e r 20th 1924.

ISSN:0368-1645    

DOI:10.1039/CT9252700150

出版商:RSC    

年代:1925

数据来源: RSC

摘要:

162 CHALLENGER JINKS AND HASLAM THE SULPHUR XXV.-The S'ulphur Compounds of Kimrneridge Shale Oil. Part I. By FREDERICK CHALLENGER JAMES RICHARD ASHWORTH JINKS , and JOHN HASLAM. THE oil obtained on distillation of the Kimrneridge shale of Dorset is characterised by a very high percentage of sulphur which is stated to be 5-8% of the crude oil.* This has prevent,ed its use * References to other shale oils rich in sulphur are given by Demesse and Reaubourg Bull. SOC. chim. 1914. [iv]. 15 625 COMPOUKDS OF KIMMERIDGE SHALE OIL. PART I. 163 as a fuel and although many attempts have been made to remove the sulphur compounds these have been unsuccessful excepting perhaps the recent hypochlorite process of Dunstan. The mode of combination of the sulphur has remained unknown (Perkin J .Inst. Pet. Tech. 1917 3 227; Manfield Zoc. cit. 1916 2 164; Craig and others Zoc. cit. 1915 4 149). Through the kindness of Mr. W. Hardy Manfield who supplied us with several gallons of the crude oil we have commenced an investigation with the object of identifying some of the sulphur compounds. The question of removing them on a commercial scale has not been considered. The only communication which contains any real information as to the ingredients of this shale oil was made by Williams (J. 1855 7 97) who only examined the bases which are sulphur-free. The peculiar odour of the oil seems to be due tlo these pyridine bases and to unsaturated hydrocarbons. I n a typical experiment 3 litres of the crude oil were distilled with steam until practically no more came over.The pale yellow oil (900 c.c.) was separated," shaken with 200 C.C. of dilute hydro-chloric acid (1 to 3) again separated and the process repeated with 100 C.C. of the acid. The mixture was shaken for an hour and left over-night. The separated oil was shaken for an hour with 150 C.C. of 10% sodium hydroxide dried over sodium sulphate, and fractionated three or four times a t 15 mm. The table shows the fractions obtained and some anaiytical results : Sulphur After KaHSO,. B. p. a t befor,- ~. - -/L--Fraction. 15 mm. A'aHSO,. S. C. H. Total. 1 35-50" 10.67 10.83 2 50-70 10.18 10.04 78-84 11.2.3 100.13 19-14 10.04 79.03 ll*OS 100.13 10.04 7s.77 11.09 99.90 3 i0-90 i.12 7-23 4 90-1 10 6-38 6-46 G * 3 9 5 110-130 5.90 6 130-145 7-04 The first two fractions (95 C.C.; 140 c.c.) formed pale yellow oils of pleasant odour which on analysis showed the presence of traces of oxygen. They were therefore separately shaken with saturated sodium bisulphite solution separated mashed and analysed. The bisulphite extracts with sodium carbonate yielded 1 C.C. of ketones, b. p. 130-136" which readily combined with semicarbazide. removed as before and the residue was added t o the main bulk. * The water (9 litres) was extracted with ether bases and phenols were. G 164 OWENGER JMKS AND HASLAM THE SULPHUR After four rectifications of fraction 1 a t the ordinary pressure (no hydrogen sulphide was evolved) fractions were obtained of which the first (b. p. 60-110") contained 14.07 and the last (b.p. above 150°) 7.82:/ of sulphur. On standing for some weeks resin was deposited doubtless arising from olefines or diolefines. On redistillation water was formed and a sharp odour observed prob-ably due to unsaturated aldehydes arising from decomposition of some oxidation product. Removal of Sulphur from Fraction b. p. 60-11Oo.-Five C.C. were slowly added to 25 C.C. of sulphuric acid a t - 15". A dark-red colour developed as with all fractions of the oil. The mixture was well shaken and after 18 hours the oil was separated washed with water and found to be free from sulphur. It gave no indo-phenin reaction nor any colour with sulphuric acid was stable to cold aqueous permanganate and had a strong odour of toluene. After nitration with sulphuric and nitric acids a t loo" the product slowly solidified to white needles containing nitrogen (m.p. and mixed m. p. with 2 4-dinitrotoluene 71"). Oxidation of the Fraction b. p . 50-70"/15 mm.-(a) With potassium pemcanganate. The oil was sealed in a bulb which was added to 200 C.C. of 2% aqueous potassium permanganate and broken by shaking. After 10 hours' shaking and addition of more permanganate till decoloration ceased the solution was filtered, acidified with hydrochloric acid and precipitated with barium chloride excess of permanganate being removed with alcohol : (1) 0.4462 gave 0.2450 BaSO,; S = 7.54. (2) 0.5106 gave 0.2830 BaSO,; S = 7.61. (3) 0.7808 gave 0.4264 BaSO,; S = 7.50. I n (3) the solution was evaporated with nitric acid to remove any oxalates.About 0.5 g. was shaken for 4 hours with 12 C.C. of water and 5 C.C. of fuming nitric acid and evaporated with hydrochloric acid and salt 0.5080 gave 0.2695 'BaSO,; S = 7.28 0.5110 gave 0.2766 BaSO,; S = 7.43. About 75% of the total sulphur is obtained as sizlphuric acid. This would indicate that alkyl sulphides and mercaptans are not a t any rate the chief sulphur compounds present whilst the cyclic polymethylene sulphides also form stable sulphones on oxidation (Trochimovski, J . Russ. Yhys. Chem. SOC. 1916 48 1 880). Identification of 2-n/lethylthiophen in a Fraction b. p . 80-1 loo.-The fraction (11 g.) mercuric acetate (80 g.) and 230 C.C. of water were shaken for 15 hours. The precipitate (36 g.) which contained much mercurous acetate due to the presence of olefines was extracted three times with hot alcohol.The insoluble residue decomposed about 225". 16 G. were distilled with 60 C.C. of hydro-(b) With nitric mid COMPOUNDS O F KIAlMERIDGE SHALE OIL. PART I. 165 chloric acid (I 2) giving about 3 C.C. of a colourless oil. This had a pure aromatic odour and gave a strong indophenin reaction. With excess of bromine water long needles m. p. 86-87" were obtained. Tribromo-2-methylthiophen melts a t 87' but when mixed with the Corresponding 3-methyl derivative non-separable mixed crystals m. p. 74" are obtained (Meyer Ber. 1885 18, 544). 3-Methylthiophen would therefore seem to be absent. 2-nl~lh~Ethiophe~imerczirlchZoride @B,*C,H,S*HgCl.-One C.C. of the regenerated oil was shaken with 10 C.C. of alcohol 100 C.C.of saturated mercuric chloride solution and 30 C.C. of 33% sodium acetate solution. The precipitate (2.6 g.) was free from mercurous chloride.* Rccrystallised from hot alcohol and then from acetone, it had m. p. 194-195" with slight previous sinfering; but when placed in the bath at 190' its m. p. was 202'. Repeated experi-ments gave no depression of the m. p. on admixture with authentic 2-methylthiophenmercurichloride. The compound was converted to niercury 2 2'-dimethyldithienyl (CH,*C41P,S),Hg hy the method of Steinkopf (Annalen 1921 424 49); m. p. and mixed m. p. 160". This was converted by mercuric bromide into 2-methylthiophen-mercuribromide (Steinkopf Zoc. cit.); m. p. and mixed m. p. 178". All these mercury derivatives of thiophen homologues were shown by Steinkopf to sinter slightly before melting.The non-depression of m. p. was however very definite. The m. p. of 2-methyl-thiophenmercurichloride was strongly depressed on admixture with the corresponding thiophen compound. IdentiJication of Thiophen.-Another specimen of the oil purified as before gave fractions b. p. 77-83" and 83-93'. With mercuric chloride and sodium acetate these gave mercurous chloride (due to olefines) and traces of a solid -which on repeated crystallisation from alcohol and acetone gave a strong indophenin reaction and was identified as thiophenmercurichloride by its m. p. and mixed m. p. (180-181"). It strongly depressed the m. p. of 2-methyl-thiophenmercurichloride. The presence of thiophen derivatives in the oil explains its behaviour on oxidation.In some cases Meyer (" Die Thiophen Gruppe," pp. 55 204) obtained very bad yields of carboxylic acids on Oxidation of the alkylthiophens owing to almost complete decomposition. We find that cold 2y0 aqueous potassium per-inanganate completely oxidises thiophen to sulphuric acid although Angeli and Alessandri (Atti R. Accad. Liizcei 1911 [vl 20 i 314) state that it is stable to alcoliolic permanganate. Our results are in general agreement with those of other workers. Scheibler (Ber. 1915 48 1815; 1916 49 2595; 1919 52 1903) * Due to previous removal of olefines with mercuric acetate 166 PRATT AND ROBINSON A SYNTHESIS OF examined shale oils rich in sulphur. His method of purification was very complicated but from a fraction of b.p. 170-180"/360 mm. he obtained with acetyl chloride and aluminium chloride a ketone possibly propylacetothienone C,H,PrS*COMe, and analysed the semicarbazone. Pfaff and Kreutzer (2. angew. Chem. 1923 36 437) identified 2-rnethylthiophen in a fraction of lignite tar by conversion into 2-methylacetothienone. THE UNIVERSITY MANCHESTER. [Received November 20th 1924. 162 CHALLENGER JINKS AND HASLAM THE SULPHUR XXV.-The S'ulphur Compounds of Kimrneridge Shale Oil. Part I. By FREDERICK CHALLENGER JAMES RICHARD ASHWORTH JINKS , and JOHN HASLAM. THE oil obtained on distillation of the Kimrneridge shale of Dorset is characterised by a very high percentage of sulphur which is stated to be 5-8% of the crude oil.* This has prevent,ed its use * References to other shale oils rich in sulphur are given by Demesse and Reaubourg Bull.SOC. chim. 1914. [iv]. 15 625 COMPOUKDS OF KIMMERIDGE SHALE OIL. PART I. 163 as a fuel and although many attempts have been made to remove the sulphur compounds these have been unsuccessful excepting perhaps the recent hypochlorite process of Dunstan. The mode of combination of the sulphur has remained unknown (Perkin J . Inst. Pet. Tech. 1917 3 227; Manfield Zoc. cit. 1916 2 164; Craig and others Zoc. cit. 1915 4 149). Through the kindness of Mr. W. Hardy Manfield who supplied us with several gallons of the crude oil we have commenced an investigation with the object of identifying some of the sulphur compounds. The question of removing them on a commercial scale has not been considered.The only communication which contains any real information as to the ingredients of this shale oil was made by Williams (J. 1855 7 97) who only examined the bases which are sulphur-free. The peculiar odour of the oil seems to be due tlo these pyridine bases and to unsaturated hydrocarbons. I n a typical experiment 3 litres of the crude oil were distilled with steam until practically no more came over. The pale yellow oil (900 c.c.) was separated," shaken with 200 C.C. of dilute hydro-chloric acid (1 to 3) again separated and the process repeated with 100 C.C. of the acid. The mixture was shaken for an hour and left over-night. The separated oil was shaken for an hour with 150 C.C. of 10% sodium hydroxide dried over sodium sulphate, and fractionated three or four times a t 15 mm.The table shows the fractions obtained and some anaiytical results : Sulphur After KaHSO,. B. p. a t befor,- ~. - -/L--Fraction. 15 mm. A'aHSO,. S. C. H. Total. 1 35-50" 10.67 10.83 2 50-70 10.18 10.04 78-84 11.2.3 100.13 19-14 10.04 79.03 ll*OS 100.13 10.04 7s.77 11.09 99.90 3 i0-90 i.12 7-23 4 90-1 10 6-38 6-46 G * 3 9 5 110-130 5.90 6 130-145 7-04 The first two fractions (95 C.C. ; 140 c.c.) formed pale yellow oils of pleasant odour which on analysis showed the presence of traces of oxygen. They were therefore separately shaken with saturated sodium bisulphite solution separated mashed and analysed. The bisulphite extracts with sodium carbonate yielded 1 C.C. of ketones, b. p. 130-136" which readily combined with semicarbazide.removed as before and the residue was added t o the main bulk. * The water (9 litres) was extracted with ether bases and phenols were. G 164 OWENGER JMKS AND HASLAM THE SULPHUR After four rectifications of fraction 1 a t the ordinary pressure (no hydrogen sulphide was evolved) fractions were obtained of which the first (b. p. 60-110") contained 14.07 and the last (b. p. above 150°) 7.82:/ of sulphur. On standing for some weeks resin was deposited doubtless arising from olefines or diolefines. On redistillation water was formed and a sharp odour observed prob-ably due to unsaturated aldehydes arising from decomposition of some oxidation product. Removal of Sulphur from Fraction b. p. 60-11Oo.-Five C.C. were slowly added to 25 C.C. of sulphuric acid a t - 15".A dark-red colour developed as with all fractions of the oil. The mixture was well shaken and after 18 hours the oil was separated washed with water and found to be free from sulphur. It gave no indo-phenin reaction nor any colour with sulphuric acid was stable to cold aqueous permanganate and had a strong odour of toluene. After nitration with sulphuric and nitric acids a t loo" the product slowly solidified to white needles containing nitrogen (m. p. and mixed m. p. with 2 4-dinitrotoluene 71"). Oxidation of the Fraction b. p . 50-70"/15 mm.-(a) With potassium pemcanganate. The oil was sealed in a bulb which was added to 200 C.C. of 2% aqueous potassium permanganate and broken by shaking. After 10 hours' shaking and addition of more permanganate till decoloration ceased the solution was filtered, acidified with hydrochloric acid and precipitated with barium chloride excess of permanganate being removed with alcohol : (1) 0.4462 gave 0.2450 BaSO,; S = 7.54.(2) 0.5106 gave 0.2830 BaSO,; S = 7.61. (3) 0.7808 gave 0.4264 BaSO,; S = 7.50. I n (3) the solution was evaporated with nitric acid to remove any oxalates. About 0.5 g. was shaken for 4 hours with 12 C.C. of water and 5 C.C. of fuming nitric acid and evaporated with hydrochloric acid and salt 0.5080 gave 0.2695 'BaSO,; S = 7.28 0.5110 gave 0.2766 BaSO,; S = 7.43. About 75% of the total sulphur is obtained as sizlphuric acid. This would indicate that alkyl sulphides and mercaptans are not a t any rate the chief sulphur compounds present whilst the cyclic polymethylene sulphides also form stable sulphones on oxidation (Trochimovski, J .Russ. Yhys. Chem. SOC. 1916 48 1 880). Identification of 2-n/lethylthiophen in a Fraction b. p . 80-1 loo.-The fraction (11 g.) mercuric acetate (80 g.) and 230 C.C. of water were shaken for 15 hours. The precipitate (36 g.) which contained much mercurous acetate due to the presence of olefines was extracted three times with hot alcohol. The insoluble residue decomposed about 225". 16 G. were distilled with 60 C.C. of hydro-(b) With nitric mid COMPOUNDS O F KIAlMERIDGE SHALE OIL. PART I. 165 chloric acid (I 2) giving about 3 C.C. of a colourless oil. This had a pure aromatic odour and gave a strong indophenin reaction. With excess of bromine water long needles m.p. 86-87" were obtained. Tribromo-2-methylthiophen melts a t 87' but when mixed with the Corresponding 3-methyl derivative non-separable mixed crystals m. p. 74" are obtained (Meyer Ber. 1885 18, 544). 3-Methylthiophen would therefore seem to be absent. 2-nl~lh~Ethiophe~imerczirlchZoride @B,*C,H,S*HgCl.-One C.C. of the regenerated oil was shaken with 10 C.C. of alcohol 100 C.C. of saturated mercuric chloride solution and 30 C.C. of 33% sodium acetate solution. The precipitate (2.6 g.) was free from mercurous chloride.* Rccrystallised from hot alcohol and then from acetone, it had m. p. 194-195" with slight previous sinfering; but when placed in the bath at 190' its m. p. was 202'. Repeated experi-ments gave no depression of the m. p. on admixture with authentic 2-methylthiophenmercurichloride.The compound was converted to niercury 2 2'-dimethyldithienyl (CH,*C41P,S),Hg hy the method of Steinkopf (Annalen 1921 424 49); m. p. and mixed m. p. 160". This was converted by mercuric bromide into 2-methylthiophen-mercuribromide (Steinkopf Zoc. cit.); m. p. and mixed m. p. 178". All these mercury derivatives of thiophen homologues were shown by Steinkopf to sinter slightly before melting. The non-depression of m. p. was however very definite. The m. p. of 2-methyl-thiophenmercurichloride was strongly depressed on admixture with the corresponding thiophen compound. IdentiJication of Thiophen.-Another specimen of the oil purified as before gave fractions b. p. 77-83" and 83-93'. With mercuric chloride and sodium acetate these gave mercurous chloride (due to olefines) and traces of a solid -which on repeated crystallisation from alcohol and acetone gave a strong indophenin reaction and was identified as thiophenmercurichloride by its m.p. and mixed m. p. (180-181"). It strongly depressed the m. p. of 2-methyl-thiophenmercurichloride. The presence of thiophen derivatives in the oil explains its behaviour on oxidation. In some cases Meyer (" Die Thiophen Gruppe," pp. 55 204) obtained very bad yields of carboxylic acids on Oxidation of the alkylthiophens owing to almost complete decomposition. We find that cold 2y0 aqueous potassium per-inanganate completely oxidises thiophen to sulphuric acid although Angeli and Alessandri (Atti R. Accad. Liizcei 1911 [vl 20 i 314) state that it is stable to alcoliolic permanganate. Our results are in general agreement with those of other workers. Scheibler (Ber. 1915 48 1815; 1916 49 2595; 1919 52 1903) * Due to previous removal of olefines with mercuric acetate 166 PRATT AND ROBINSON A SYNTHESIS OF examined shale oils rich in sulphur. His method of purification was very complicated but from a fraction of b. p. 170-180"/360 mm. he obtained with acetyl chloride and aluminium chloride a ketone possibly propylacetothienone C,H,PrS*COMe, and analysed the semicarbazone. Pfaff and Kreutzer (2. angew. Chem. 1923 36 437) identified 2-rnethylthiophen in a fraction of lignite tar by conversion into 2-methylacetothienone. THE UNIVERSITY MANCHESTER. [Received November 20th 1924.

ISSN:0368-1645    

DOI:10.1039/CT9252700162

出版商:RSC    

年代:1925

数据来源: RSC

摘要:

166 PRATT AND ROBINSON A SYNTHESIS OF XXV1.-A Synthesis of Pyrylium Salts of Anthocyanidin Type. Part V. The Xynthesis of Cyanidin Chloride and of Delphinidin Chloride. By DAVID Do~a PRATT and ROBERT ROBINSON. IN Part I1 (J. 1923 123 750) it was shown that w-methoxy-acetoveratrone (I) can be obtained by the methylation of w-hydroxy-acetoveratrone by means of silver oxide and methyl iodide. The oily product yielded isomeric semicarbazones C1,H,,04N3 (a) m. p. 205" and ( b ) m. p. 168" whilst condensation with p-resorcylaldehyde in presence of hydrogen chloride gave rise to a pyrylium salt characterised as the ferrichloride C18H1,0,CI,Fe m. p. 156". The unsatisfactory character of the process is emphasised in the memoir quoted and as a preliminary to an attempt to synthesise cyanidin chloride it was clearly essential to work out an entirely novel method of prepara1;ion of o-methoxyacetoveratrone.We desired to proceed from veratric acid in order that the process might subsequently be applied to the trimethyl ether of gallic acid and so lead t o a synthesis of delphinidin salts. After unsuccessful trials in other directions e.g. in attempting the decomposition of diazoacetophenones by methyl alcohol the solution of the problem was found in an application of the synthesis of acetophenone from benzoyl chloride by way of ethyl benzoylacetate. The action of sodium on ethyl methoxyacetate leads to the sodio-derivative of ethyl ay-dimethoxyacetoacetate MeO*CH,-CO*CH(OMe)*CO,Et, which readily yields C-aroyl derivatives. Ethyl q-dimethoxy- a-benzoylacetoacetate was decomposed by boiling dilute sulphuric acid with formation of phenylglyoxal in poor yield but when it was subjected to the prolonged action of cold dilute potassium hydroxide and the mixture was subsequently boiled w-methoxy-acetophenone (Part 11 p.748) was obtained in accordance with the scheme : PYRYLIUN SALTS OF ANTHOCYASIDIN TYPE. PART v. 167 FO*CH,*OMe - + Ph*CO*CH,*OMe + MeO*CH,*CO,K Ph*CO*C( OMe)*CO,Et +3K0H + K,CO + EtOH. I n a similar manner w 4-dimethoxyacetophenone (Part 11, p. 750) was derived from anisic acid and the product of the inter-action of ethyl sodio-q-dimethoxyacetoacetate and veratroyl chloride in dry ethereal solution yielded w-methoxyacetoveratrone on careful hydrolysis with alkali. The analogous preparation of w 3 4 5-tetramethoxyacetophenone (11) offered no difficulty.Pure w-methoxyacetoveratrone is a crystalline substance which gives a single semicarba,zone m. p. 178" and this is identical with the previously described verstrylmethoxyacetaldehydesemicarb-azone-b the melting point of which was slowly raised to 178" by repeated crystallisation. Veratrylrnethoxyacetddehydesemicarb-azone-a m. p. 205" was the more sparingly solnble of the isomerides and its melting point is not raised on recrystallisation. This sub-stance is plainly the semicarbazone of a 3 4-trirnethoxyphenyl-acetaldehyde (111) and the formation of the latter in the methyl-ation of veratroylcarbinol is noteworthy. MeO/\CO*CH,*OMe MeO/\CO*CH,*OMe MeO/'\CH( OMe)*CI-f (3 MeO!, I MeO!,,! MeOl\) Me0 (1.) (11.) (III.) w-Methoxyacetoveratrone and w 3 4 5tetramethoxyaceto-phenone are much more soluble in cold than in hot water a pro-perty which doubtless indicates the formation and decomposition of hydrates.The former ketone on condensation with P-resorcyl-aldehyde in presence of hydrogen chloride yields trimethylfisetinidin chloride (IV) and the derived ferrichloride m. p. 156" is identical with the substance obtained as mentioned above. 2-Hydroxy-4 6-dimethoxybenzaldehyde and W-methoxyacetoveratrone con-dense under the agency of hydrogen chloride in ethereal solution with formation of cyanidin chloride pentamethyl ether (V) and this salt is demethylated by means of boiling hydriodic acid in presence of phenol with formation of cyanidin iodide.Cyanidin chloride (VI) was prepared from the iodide in the usual manner and the product exhibited in every detail the properties of cyanidin chloride of natuml origin as described by Willstatter and Everest (Annulen 1913 401 189) and Willstiitter and Nolan (ibid. 1915, 408 13). A direct comparison of the synthetical material with an authentic specimen disclosed no dif€erences existing between them. The production of cyanidin chloride by the reduction of quercetin in acid solution (Willstatter and Mallison Sitxungsber. Preu-ss 16s PR-4TT AND ROBINSON A SYNTHESIS OF Akad. Wiss. 1914 769) constitutes in one sense a synthesis of the substance and furthermore Willstatter and Kindler in 1919 made 8 communication to the Munchner Chemische Gesellschaft con-cerning experiments which they had conducted on the application of the Willstatter-Zechmeister pelargonidin synthesis to the case of cyanidin (‘‘ Wissenschaftliche E’orschungsberichte 111 Organische Chemie,” R.Pummerer 2nd Edition 1923 150). The details of the results obtained are not yet available.” c1 n 0 OMe c1 0 F-(VII.) The synthesis of delphinidin chloride (VII) followed the lines of that of cyanidin chloride delphinidin chloride hexamethyl ether being obtained from hydroxydimethoxybenzaldehyde and o 3 4 5-tetramethoxyacetophenone (11). As shown in the ex-perimental portion on page 174 there can be no doubt as to the identity of the synthetical product obtained on demethylation, with that of natural origin. E Y P E R I M E N T A L .Ethgl uy-Dimethoxyacetoccetate.-Ethyl chloroacetate (I22 9.) was gradually added with cooling and shaking to a solution of sodium methoxide (from 23 g. of sodium) in anhydrous methyl alcohol (200 c.c.). The mixture was refluxed until neutral most of the alcohol then removed a.nd the residue mixed with brine and ether. The dried ethereal solution on fractionation yielded 85 g. of ethyl methoxyacetste b. p. 1 3 1 O . j - Sodium (8 g.) cut in thin slices, * Willsttitter Zechmeister and Kindler have now published their work (Ber. 1924 57 [B] 1938). 5 This substance can also be obtained by the hydrolysis of methoxy-acetonitrile by Pinner’s method. Ethyl ethoxyacetate (Henry? Ber. 1871, 4 706) ; ethyl ay-diethoxyacetoacetate (Conrad Ber. 1878 11 58 ; Erlen-bach Annalen 1892 269 28).In order t o avoid the possibility of replace PYRYLIUM SALTS OF ANTHOCYAXIDIN TYPE. PART V. 169 was added in one portion to ethyl methoxyacetate (100 g.) ; the reaction which soon commenced was controlled by cooling in melting ice when necessary. The thick syrup which resulted was treated with 50% acetic acid (45 c.c.) and saturated brine and extracted with ether. The ethereal layer was separated washed with aqueous sodium cerbonate dried with anhydrous sodium sulphate and distilled; 40 g. of a colourless oil b. p. 130"/15 mm., were obtained (Found C = 50.4; H = 7.4. C,H,,O requires C = 50.5; €1 = 7.4%). This ester is moderately readily soluble in water and its alcoholic solution gives a violet coloration with ferric chloride the shade being bluer than that developed by ethyl acetoacetate under similar conditions.w 4-DimetAox~aceto~henone.-In the first place experiments on the hydrolysis of the condensation product from ethyl sodio-ay-dimethoxyacetoacetate and benzoyl chloride were made. After boiling with dilute sulphuric acid and distillation in a current of steam a yellow distillate was obtained and this by suitable treat-ment yielded phenylglyoxaldiphenylhydrazone m. p. 152". When, however the product was boiled with dilute aqueous sodium hydroxide o-methoxyacetophenone was obtained in small yield and identified as the semicarbazona m. p. 85". w 4-Dimethoxy-acetophenone may be obtained in the following manner Sodium (2.7 g.) was granulated under toluene washed with ether suspended in anhydrous ether (150 c.c.) and ethyl ay-dimethoxyacetoacetate (22.3 g.) gradually added.A sodio-derivative separated from the solution and when the sodium had disappeared anisoyl chloride (20 g.) was added in one portion. A gentle reaction occurred and after 1 hour the process was completed by heating on the steam-bath under reflux during 4 hours. Next day water was added the ethereal layer dried over sodium sulphate and after removal of the solvent 35 g. of a pale yellow oil remained. The whole wag agitated for 12 hours with 2.5% aqueous potassium hydroxide (500 c.c.) and the liquid then boiled for 3 hours cooled nearly saturated with potassium carbonate and extracted with ether ; 7.5 g. of the ketone m. p. 40° were obtained. On condensation with 6-aminopiperonal in alcoholic solution by means of potassium hydroxide o 4-dimethoxyacetophenone yields ment of the ethyl group of the esters by methyl and the production of mixtures Mr.N. L. Matthews has employed methyl chloroacetate and condensed this with sodium methoxide in dry methyl-alcoholic solution in the cold. Methyl chloroacetate (108 g.) yielded methyl methoxyacetate (70 g.) b. p. 129'1754 mm. Methyl methoxyacetate (100 g.) reacted with sodium (9 g.) to give a product from which methyl ay-dimethoxyxetoacetata b. p. 129'/17 mm. could be isolated (Found C = 47.5; H = 7.1. C,H,,O requires C = 47.7; R = 6.8%). The yield was 40-50% of that required by theory. G 170 PRATT AND ROBINSON A SYNTHESIS OF 3-methoxy-6 7-methylenedioxy-2-(4-methoxyphenyl)quinoline which crystallises from methyl alcohol in colourless laminze m.p. 152". o-Metlho~yucetoveratrone (I).-Ethyl ay-dimethoxyacetoacetate (36.2 g.) was gradually added to finely granulated sodium (4.4 g.) suspended in anhydrous ether (225 c.c.). Formation of the sodio-derivative appeared to be complete after an hour and a solution of distilled veratroyl chloride (38 g.) in ether (150 c.c.) was intro-duced causing a mild reaction. The mixture was gently heated on the steam-bath for 2 hours allowed t o remain over-night and heated during a further 2 hours. After washing with water drying, and evaporating the ether there remained 63 g. of a pale orange, viscous liquid which could not be crystallised. The whole product was hydrolysed by vigorous agitation €or 9 hours with cold 2.5% aqueous potassium hydroxide (800 c.c.) and finally by boiling the clear solution for 5 hours.The ketone was isolated by extraction with ether after the addition of much potassium carbona$e and purified by distillation; 22 g. of an oil b. p. 190"/15 mm. were obtained which solidified. The substance crystallises from light petroleum containing a little benzene in colourless prisms m. p. 62" (Found C = 63.1 ; H = 6.8. C,,H,,O requires C = 62-9; H = 607%). When a little of this substance is melted under water and the mixture cooled a clear solution is obtained from which the ketone may be precipitated as an oil either by heating or by the addition of an alkali carbonate or hydroxide. The substance is very readily soluble in organic solvents with the exception of light petroleum.On condensation with 6-aminopiperonal it yields 3 - methoxy - 6 7 - msthylenedioxy-2 -(3 4-dimethoxypheiayl)quinoline, which crystallises from ethyl alcohol in slender needles m. p. 155", and exhibits a violet fluorescence in alcoholic solution. Fisetinidin Chloride Trimethyl Ether (IV) . A slow stream of hydrogen chloride was passed through an ice-cold solution of p-resorcylaldehyde (2 g . ) and o-methoxyaceto-veratrone (3 g . ) in dry ether (40 c.c.) when the liquid became yellow and then red and crystalbation commenced after 20 minutes. The passage of the gas was discontinued after 30 minutes and after several hours the pyrylium salt which exhibited an intense green lustre was collected washed with ether and dried (3-4 g.).The ethereal mother-liquors were washed with dilute hydrochloric acid and a ferrichloride (0.2 g . ) was precipitated. This derivative crystallises from acetic acid in reddish-brown needles m. p. 156", and its properties are identical with those of the ferrichloride previously prepared from the product of methylation of veratroyl-carbinol (loc. cit. ). Fisetinidin chloride trimethyl ether dissolves i PYRYLIUM S,4LTS O F SNTHOCYANIDIX TYPE. PART V. 17 1 hot 70/6 hydrochloric acid to an orange-red solut'ion and separate.3 completely on cooling in reddish- brown prismatic needles exhibiting a green reflex (Found in material dried in a vacuum C = 56.1 : H = 3.3. This salt darkens a t 135" and decomposes a t 188-189". It is reddish-violet by transmitted light and makes a violet smcar on paper.1 ts alcoholic solutions are intensely reddish-violet and the orange solution in concentrated sulphuric acid exhibits a green fluorescence. Sparingly soluble in cold water it dissolves on warming to an orange-red solution which on dilution is rapidly decolorised with formation of the $-base. The violet colour-base is precipitated when sodium acetate is added to a moderately concentrated aqueous solution of the salt hut if a dilute solution is treated with sodium acetate the appearance of the violet colour is transient and the +-base is obtained. isoAmyl alcohol extracts the salt completely from an acid aqueous solution and the addition of sodium acetate to the red alcoholic extract gives a violet solution the colour of which fades.The oxonium salt is regenerated from solutions of the colour-base and $-base by the addition of hydrochloric acid. Cl,K1,O,Cl,BH,O requires C = 56-2 ; H = 5.5%). Cyaizidiii Chloride Pentamethyl Ether (V). I n order t o obtain good results in this preparation it is very necessary that the materials employed should be pure. Hydrogen chloride was passed for 1 hour through a solution of 2-hydroxy-4 5-dimethouybenzaldehyde (4-5 g.) and w-methosyacetoveratrone (5-2 g.) in ether (50 c.c.). The solution quickly became crimson and crystallisation of the product was induced by scratching after 30 minutes from the commencement. The tube containing the mixture and a dish containing solid potassium hydroxide were together covered by a bell-jar and after several hours the salt was collected washed with ether and dried (5.5 g.).The salt crystal-lises from alcohol containing a little hydrogen chloride in small, red necdles m. p. 152" which in mass exhibit an old-gold sheen, but give a chocolate-brown smear on paper (Found in material dried in a vacuum over phosphoric oxide and potassium hydroxide : C = 51.7 ; H = 5.9 ; C1 = 14.9. C,,,H,,B,Cl,HCl,2H20 requires C = 51.6; H = 5.6; C1 = 15.2%). The same dtchloride crystal-lised from a mixture of alcohol and concentrated aqueous hydro-chloric acid in slender needles m. p. 152" (Found C = 51.5; H = 5.5; C1 = 15.4%). From 776 aqueous hydrochloric acid the salt separates in long orange-brown needles which form a crystalline crust exhibiting a green reflex (Found in material dried in a vacuum C = 53-2 ; H = 6.0.C,,H,,O,C1,3H,O requires C = 53-7 ; H = 6.00/,). The substance is readily soluble in the simple c," 172 PRATT AND ROBINSON A SYNTHESIS OF alcohols to reddish-violet solutions the colour of which fades on dilution with water and can then be restored by the addition of a mineral acid. The ferrichloride crystallises from acetic acid in which it is very sparingly soluble in reddish-brown prismatic needles m. p. 196200' (decomp.) exhibiting a bronze lustre. The chloride is insoluble in chloroform but this derivative is moderately readily soluble and when the hot saturated solution is rapidly concentrated to one-quarter of its bulk the ferrichloride separates in microscopic needles exhibiting an intense green lustre.Cyanidin Chloride (VI). The foregoing pentamethyl ether (3.2 g.) and phenol (15 g.) were added to hydriodic acid (180 c.c.; d 1.7) and the mixture was boiled for 30 minutes in an atmosphere of carbon dioxide. Water (2 vols.) and much ether were added to the cooled solution and on standing glistening needles with a bright green reflex separated. The substance (1.8 g.) had properties identical with those of cyanidin iodide prepared by the demethylation of paeonidin chloride of natural origin (Willstatter and Nolan AnnaZen 1915 408 136). The iodide (3 g.) was thoroughly ground with aqueous sodium acetate the bluish-violet colour-base separated thoroughly washed, and heated to boiling with 3% aqueous hydrochloric acid (100 c.c.) in presence of a trace of silver and filtered 50 C.C.more 3% hydrochloric acid being used for washing. Concentrated hydro-chloric acid (50 c.c.) was added and on standing the dark red solution deposited the salt completely in masses of short reddish-brown prisms that had a green lustre (Found C = 52.5 ; H = 4.1. C1,HllO,C1,H,O requires C = 52.8; H = 343%). This product showed all the characteristic reactions of cyanidin chloride and a direct comparison with a specimen of the substance of natural origin disclosed no difference in properties of any kind. The behaviour on heating appearance of the crystals under the micro scope formation of colour-base and +-base solubilities in aqueous and alcoholic acid solutions colour of acid solutions absorption spectrum of the solution in ethyl alcohol and the reactions with ferric chloride sodium carbonate sodium acetate potassium acetate in alcoholic solution lead acetate and Fehling's solution were all examined.Willstatter and Everest (Zoc. cit.) state that cyanidin on oxidation with hydrogen peroxide yields a yellow crystalline product closely resembling a flavonol colouring matter. There is, however no clear evidence that quercetin can be obtained by the oxidation of cyanidin and furthermore it is remarkable that no chromone or chromonol derivative has yet been prepared by oxidising a benzopyrylium salt. We have made numerous experi PYRYLIUM SALTS OY ANTHOCYANIDIN TYPE. PART v. 173 ments with the object of achieving this transformation but any definite products isolated have been either carboxylic acids or cournarin derivatives.This investigation proceeds. w 3 4 5-Tetramethxyacetophenone (II).-Sodium (2.5 g.), granulated under toluene and washed with ether was suspended in ether (120 c.c.) and ethyl ccy-dimethoxyacetoacetate (20 8.) slowly added. When the formation of the sodio-derivative appeared to be complete an ethereal solution of trimethylgalloyl chloride (24.5 g.) was added in one portion and the mixture heated gently on the steam-bath for 8 hours. The product was isolated (34 9.) and shaken for 12 hours with 2.5% aqueous potassium hydroxide. The solution was boiled for 4 hours and the ketone isolated as in the case of w-methoxyacetoveratrone. The yield was 9 g. of a colourless oil b. p. 212"/15 mm. which solidified in contact with light petroleum.The substance crystallises from benzene-light petroleum in colourless needles m. p. 54" and closely resembles w-methoxyacetoveratrone (Found C = 60.0; H = 6.3. C,,H,,O, requires C = 60-0; H = 6.6%). The semicarbaxone crystalliser from aqueous alcohol in long colourless needles m. p. 158". 3-Metltoxy-6 ?-methylenedioxy-2-(3 4 5-trimethoxyphenyl)quinoE-ine crystallises from ethyl alcohol in colourless needles m. p. 159", and exhibits a violet fluorescence in alcoholic solution. Its salts, e.g. the sparingly soluble hydrochloride are yellow. The metho-svlphute is orange-yellow and it is evident from a comparison of this substance with the intensely coloured delphinidin chloride hexamethyl ether that the quinolinium and benzopyryhm nuclei function quite differently as chromophores.It may well be that the methoxyl groups are able to decentralise the cationic valency of the pyrylium nucleus and so produce changes of orbits of electrons owing to recurrent redistribution of the charge whilst on the other hand the powerfully basic quinolinium nucleus is able to ignore the claims of the weak auxochromes. We are thus led to anticipate that the aminophenylquinolinium salts will resemble tinctorially the related hydroxyphenylbenzopyrylium salts and it is hoped that an experimental test of this point will be made. Delphinidin Chloride Hexamethgl Ether (corresponding with VII). Hydrogen chloride was passed through an ice-cold solution of w 3 4 5-tetramethoxyacetophenone (4 g.) and 2-hydroxy-4 6-dimethoxybenzaldehyde (3 g.) in dry ether (50 c.c.) crystallisation of the product in crimson needles and prisms having a dark green reflex occurring after about 1 hour.Next day the salt (4 g . ) was collected and a further quantity (0.7 g.) was obtained from the ethereal mother-liquor. The substance crystallises from alcoho 174 A SYNTHESIS OF PYRYLIUM SALTS OF ANTHOCYANIDIN TYPE. containing a trace of hydrogen chloride in long red needles m. p. 163-164" (Found in material dried in a vacuum C = 58.5 ; H = 5.8. C21H,30,CI,0-5H20 requires C = 58.4; H = 5.6%). The substance exhibits a green lustre and is reddish-violet by transmitted light. It is readily soluble in the simple alcohols and moderately soluble in chloroform to a reddish-violet solution. The dark red colour of the solution in water rapidly fades and an almost colourless $-base is precipitated.Faintly acid solutions are also decolorised on great dilution but addition of acid restores the colour of the pyrylium salt. The ferrichloride crystalhes from glacial acetic acid in brownish-red needles which have a dark green appearance in mass. This derivative m. p. 169-170" is readily soluble in acetone chloroform or the simple alcohols. The sulphate crystallises from dilute sulphuric acid in slender red needles with green reflex m. p. 225" (decomp.). Delphinidin Chloride (VII). Delphinidin chloride hexamethyl ether (3-0 g.) was demethylated by means of a boiling mixture of hydriodic acid (180 c.c.; d 1.7) and phenol (15 g.) during 30 minutes a slow current of carbon dioxide being passed through the containing vessel.The cooled liquid deposited clusters of long pointed brown needles together with some squat prisms and these were collected washed with ether and dried (2.0 g.). The iodide was converted into chloride by treatment a t 60" with silver chloride in alcoholic solution in a silver-mirrored vessel. The filtered solution was mixed with an equal volume of concentrated hydrochloric acid and the amorphous precipitate so obtained allowed to remain when it slowly became resolved into a mass of microscopic needles. The substance was isolated and crystallised by solution in 5% hydrochloric acid and addition of 30% acid to the filtered solution so as to make the concentration of hydrochloric acid about 25%. The brown, crystalline mass was dried in a vacuum (Found C = 49.4; H = 4-0.C1,Hl10,Cl,1~5H20 requires C = 49.4; H = 3-8 ; H20 = 7.4y0). According to Willstatter and Weil (Annalen 1916 412, 178) delphinidin chloride crystallises from hydrochloric acid of 20% or greater concentrations with 1.5H20 which is completely lost in a vacuum. Our product did not behave in this way but the circumstance was an accident since when the material was powdered and again exposed to a vacuum it lost 7.6%. The anhydrous salt does not melt below 350". The hydrates containing 1H20 2H20 and 4H20 have been prepared by the methods devised by Willstatter and Weil in order to observe the crystalline forms, which were found to agree with the descriptions of these authors SYNTHESIS OF CERTAIN HIGHER ALIPHATIC COMPOUNDS.PART I. 175 The absorption spectrum of an alcoholic solution of the chloride, the formation of the +base the behaviour of aqueous and acid solutions on shaking with ether ethyl acetate and isoamyl alcohol, the reactions with ferric chloride in aqueous and alcoholic solutions and with sodium carbonate sodium bisulphite lead acetate and Fehling’s solution were all examined with results identical with those described in the case of delphinidin chloride of natural origin by Willstatter and Mieg (AnnaZen 1915 408 61) and Willstatter and Weil (Zoc. cit.). We were not able to make a direct comparison, but the properties of delphinidin chloride are so characteristic and have been recorded in such detail that we can entertain no doubt as to the identity of the synthetical product with that obtained by the hydrolysis of the pigments of the wild purple larkspur and the blue-black pansy.One of us (D. D. P.) desires to thank the Carnegie Trust for t3he Universities of Scotland for a Fellowship which has enabled him to take part in this investigation. THE UNIVERSITY MANCHESTER. [Received November 3 ~ d 1924. 166 PRATT AND ROBINSON A SYNTHESIS OF XXV1.-A Synthesis of Pyrylium Salts of Anthocyanidin Type. Part V. The Xynthesis of Cyanidin Chloride and of Delphinidin Chloride. By DAVID Do~a PRATT and ROBERT ROBINSON. IN Part I1 (J. 1923 123 750) it was shown that w-methoxy-acetoveratrone (I) can be obtained by the methylation of w-hydroxy-acetoveratrone by means of silver oxide and methyl iodide. The oily product yielded isomeric semicarbazones C1,H,,04N3 (a) m.p. 205" and ( b ) m. p. 168" whilst condensation with p-resorcylaldehyde in presence of hydrogen chloride gave rise to a pyrylium salt characterised as the ferrichloride C18H1,0,CI,Fe m. p. 156". The unsatisfactory character of the process is emphasised in the memoir quoted and as a preliminary to an attempt to synthesise cyanidin chloride it was clearly essential to work out an entirely novel method of prepara1;ion of o-methoxyacetoveratrone. We desired to proceed from veratric acid in order that the process might subsequently be applied to the trimethyl ether of gallic acid and so lead t o a synthesis of delphinidin salts. After unsuccessful trials in other directions e.g. in attempting the decomposition of diazoacetophenones by methyl alcohol the solution of the problem was found in an application of the synthesis of acetophenone from benzoyl chloride by way of ethyl benzoylacetate.The action of sodium on ethyl methoxyacetate leads to the sodio-derivative of ethyl ay-dimethoxyacetoacetate MeO*CH,-CO*CH(OMe)*CO,Et, which readily yields C-aroyl derivatives. Ethyl q-dimethoxy- a-benzoylacetoacetate was decomposed by boiling dilute sulphuric acid with formation of phenylglyoxal in poor yield but when it was subjected to the prolonged action of cold dilute potassium hydroxide and the mixture was subsequently boiled w-methoxy-acetophenone (Part 11 p. 748) was obtained in accordance with the scheme : PYRYLIUN SALTS OF ANTHOCYASIDIN TYPE. PART v. 167 FO*CH,*OMe - + Ph*CO*CH,*OMe + MeO*CH,*CO,K Ph*CO*C( OMe)*CO,Et +3K0H + K,CO + EtOH.I n a similar manner w 4-dimethoxyacetophenone (Part 11, p. 750) was derived from anisic acid and the product of the inter-action of ethyl sodio-q-dimethoxyacetoacetate and veratroyl chloride in dry ethereal solution yielded w-methoxyacetoveratrone on careful hydrolysis with alkali. The analogous preparation of w 3 4 5-tetramethoxyacetophenone (11) offered no difficulty. Pure w-methoxyacetoveratrone is a crystalline substance which gives a single semicarba,zone m. p. 178" and this is identical with the previously described verstrylmethoxyacetaldehydesemicarb-azone-b the melting point of which was slowly raised to 178" by repeated crystallisation. Veratrylrnethoxyacetddehydesemicarb-azone-a m.p. 205" was the more sparingly solnble of the isomerides and its melting point is not raised on recrystallisation. This sub-stance is plainly the semicarbazone of a 3 4-trirnethoxyphenyl-acetaldehyde (111) and the formation of the latter in the methyl-ation of veratroylcarbinol is noteworthy. MeO/\CO*CH,*OMe MeO/\CO*CH,*OMe MeO/'\CH( OMe)*CI-f (3 MeO!, I MeO!,,! MeOl\) Me0 (1.) (11.) (III.) w-Methoxyacetoveratrone and w 3 4 5tetramethoxyaceto-phenone are much more soluble in cold than in hot water a pro-perty which doubtless indicates the formation and decomposition of hydrates. The former ketone on condensation with P-resorcyl-aldehyde in presence of hydrogen chloride yields trimethylfisetinidin chloride (IV) and the derived ferrichloride m.p. 156" is identical with the substance obtained as mentioned above. 2-Hydroxy-4 6-dimethoxybenzaldehyde and W-methoxyacetoveratrone con-dense under the agency of hydrogen chloride in ethereal solution with formation of cyanidin chloride pentamethyl ether (V) and this salt is demethylated by means of boiling hydriodic acid in presence of phenol with formation of cyanidin iodide. Cyanidin chloride (VI) was prepared from the iodide in the usual manner and the product exhibited in every detail the properties of cyanidin chloride of natuml origin as described by Willstatter and Everest (Annulen 1913 401 189) and Willstiitter and Nolan (ibid. 1915, 408 13). A direct comparison of the synthetical material with an authentic specimen disclosed no dif€erences existing between them.The production of cyanidin chloride by the reduction of quercetin in acid solution (Willstatter and Mallison Sitxungsber. Preu-ss 16s PR-4TT AND ROBINSON A SYNTHESIS OF Akad. Wiss. 1914 769) constitutes in one sense a synthesis of the substance and furthermore Willstatter and Kindler in 1919 made 8 communication to the Munchner Chemische Gesellschaft con-cerning experiments which they had conducted on the application of the Willstatter-Zechmeister pelargonidin synthesis to the case of cyanidin (‘‘ Wissenschaftliche E’orschungsberichte 111 Organische Chemie,” R. Pummerer 2nd Edition 1923 150). The details of the results obtained are not yet available.” c1 n 0 OMe c1 0 F-(VII.) The synthesis of delphinidin chloride (VII) followed the lines of that of cyanidin chloride delphinidin chloride hexamethyl ether being obtained from hydroxydimethoxybenzaldehyde and o 3 4 5-tetramethoxyacetophenone (11).As shown in the ex-perimental portion on page 174 there can be no doubt as to the identity of the synthetical product obtained on demethylation, with that of natural origin. E Y P E R I M E N T A L . Ethgl uy-Dimethoxyacetoccetate.-Ethyl chloroacetate (I22 9.) was gradually added with cooling and shaking to a solution of sodium methoxide (from 23 g. of sodium) in anhydrous methyl alcohol (200 c.c.). The mixture was refluxed until neutral most of the alcohol then removed a.nd the residue mixed with brine and ether. The dried ethereal solution on fractionation yielded 85 g. of ethyl methoxyacetste b.p. 1 3 1 O . j - Sodium (8 g.) cut in thin slices, * Willsttitter Zechmeister and Kindler have now published their work (Ber. 1924 57 [B] 1938). 5 This substance can also be obtained by the hydrolysis of methoxy-acetonitrile by Pinner’s method. Ethyl ethoxyacetate (Henry? Ber. 1871, 4 706) ; ethyl ay-diethoxyacetoacetate (Conrad Ber. 1878 11 58 ; Erlen-bach Annalen 1892 269 28). In order t o avoid the possibility of replace PYRYLIUM SALTS OF ANTHOCYAXIDIN TYPE. PART V. 169 was added in one portion to ethyl methoxyacetate (100 g.) ; the reaction which soon commenced was controlled by cooling in melting ice when necessary. The thick syrup which resulted was treated with 50% acetic acid (45 c.c.) and saturated brine and extracted with ether.The ethereal layer was separated washed with aqueous sodium cerbonate dried with anhydrous sodium sulphate and distilled; 40 g. of a colourless oil b. p. 130"/15 mm., were obtained (Found C = 50.4; H = 7.4. C,H,,O requires C = 50.5; €1 = 7.4%). This ester is moderately readily soluble in water and its alcoholic solution gives a violet coloration with ferric chloride the shade being bluer than that developed by ethyl acetoacetate under similar conditions. w 4-DimetAox~aceto~henone.-In the first place experiments on the hydrolysis of the condensation product from ethyl sodio-ay-dimethoxyacetoacetate and benzoyl chloride were made. After boiling with dilute sulphuric acid and distillation in a current of steam a yellow distillate was obtained and this by suitable treat-ment yielded phenylglyoxaldiphenylhydrazone m.p. 152". When, however the product was boiled with dilute aqueous sodium hydroxide o-methoxyacetophenone was obtained in small yield and identified as the semicarbazona m. p. 85". w 4-Dimethoxy-acetophenone may be obtained in the following manner Sodium (2.7 g.) was granulated under toluene washed with ether suspended in anhydrous ether (150 c.c.) and ethyl ay-dimethoxyacetoacetate (22.3 g.) gradually added. A sodio-derivative separated from the solution and when the sodium had disappeared anisoyl chloride (20 g.) was added in one portion. A gentle reaction occurred and after 1 hour the process was completed by heating on the steam-bath under reflux during 4 hours. Next day water was added the ethereal layer dried over sodium sulphate and after removal of the solvent 35 g.of a pale yellow oil remained. The whole wag agitated for 12 hours with 2.5% aqueous potassium hydroxide (500 c.c.) and the liquid then boiled for 3 hours cooled nearly saturated with potassium carbonate and extracted with ether ; 7.5 g. of the ketone m. p. 40° were obtained. On condensation with 6-aminopiperonal in alcoholic solution by means of potassium hydroxide o 4-dimethoxyacetophenone yields ment of the ethyl group of the esters by methyl and the production of mixtures Mr. N. L. Matthews has employed methyl chloroacetate and condensed this with sodium methoxide in dry methyl-alcoholic solution in the cold. Methyl chloroacetate (108 g.) yielded methyl methoxyacetate (70 g.) b.p. 129'1754 mm. Methyl methoxyacetate (100 g.) reacted with sodium (9 g.) to give a product from which methyl ay-dimethoxyxetoacetata b. p. 129'/17 mm. could be isolated (Found C = 47.5; H = 7.1. C,H,,O requires C = 47.7; R = 6.8%). The yield was 40-50% of that required by theory. G 170 PRATT AND ROBINSON A SYNTHESIS OF 3-methoxy-6 7-methylenedioxy-2-(4-methoxyphenyl)quinoline which crystallises from methyl alcohol in colourless laminze m. p. 152". o-Metlho~yucetoveratrone (I).-Ethyl ay-dimethoxyacetoacetate (36.2 g.) was gradually added to finely granulated sodium (4.4 g.) suspended in anhydrous ether (225 c.c.). Formation of the sodio-derivative appeared to be complete after an hour and a solution of distilled veratroyl chloride (38 g.) in ether (150 c.c.) was intro-duced causing a mild reaction.The mixture was gently heated on the steam-bath for 2 hours allowed t o remain over-night and heated during a further 2 hours. After washing with water drying, and evaporating the ether there remained 63 g. of a pale orange, viscous liquid which could not be crystallised. The whole product was hydrolysed by vigorous agitation €or 9 hours with cold 2.5% aqueous potassium hydroxide (800 c.c.) and finally by boiling the clear solution for 5 hours. The ketone was isolated by extraction with ether after the addition of much potassium carbona$e and purified by distillation; 22 g. of an oil b. p. 190"/15 mm. were obtained which solidified. The substance crystallises from light petroleum containing a little benzene in colourless prisms m.p. 62" (Found C = 63.1 ; H = 6.8. C,,H,,O requires C = 62-9; H = 607%). When a little of this substance is melted under water and the mixture cooled a clear solution is obtained from which the ketone may be precipitated as an oil either by heating or by the addition of an alkali carbonate or hydroxide. The substance is very readily soluble in organic solvents with the exception of light petroleum. On condensation with 6-aminopiperonal it yields 3 - methoxy - 6 7 - msthylenedioxy-2 -(3 4-dimethoxypheiayl)quinoline, which crystallises from ethyl alcohol in slender needles m. p. 155", and exhibits a violet fluorescence in alcoholic solution. Fisetinidin Chloride Trimethyl Ether (IV) . A slow stream of hydrogen chloride was passed through an ice-cold solution of p-resorcylaldehyde (2 g .) and o-methoxyaceto-veratrone (3 g . ) in dry ether (40 c.c.) when the liquid became yellow and then red and crystalbation commenced after 20 minutes. The passage of the gas was discontinued after 30 minutes and after several hours the pyrylium salt which exhibited an intense green lustre was collected washed with ether and dried (3-4 g.). The ethereal mother-liquors were washed with dilute hydrochloric acid and a ferrichloride (0.2 g . ) was precipitated. This derivative crystallises from acetic acid in reddish-brown needles m. p. 156", and its properties are identical with those of the ferrichloride previously prepared from the product of methylation of veratroyl-carbinol (loc. cit. ). Fisetinidin chloride trimethyl ether dissolves i PYRYLIUM S,4LTS O F SNTHOCYANIDIX TYPE.PART V. 17 1 hot 70/6 hydrochloric acid to an orange-red solut'ion and separate.3 completely on cooling in reddish- brown prismatic needles exhibiting a green reflex (Found in material dried in a vacuum C = 56.1 : H = 3.3. This salt darkens a t 135" and decomposes a t 188-189". It is reddish-violet by transmitted light and makes a violet smcar on paper. 1 ts alcoholic solutions are intensely reddish-violet and the orange solution in concentrated sulphuric acid exhibits a green fluorescence. Sparingly soluble in cold water it dissolves on warming to an orange-red solution which on dilution is rapidly decolorised with formation of the $-base. The violet colour-base is precipitated when sodium acetate is added to a moderately concentrated aqueous solution of the salt hut if a dilute solution is treated with sodium acetate the appearance of the violet colour is transient and the +-base is obtained.isoAmyl alcohol extracts the salt completely from an acid aqueous solution and the addition of sodium acetate to the red alcoholic extract gives a violet solution the colour of which fades. The oxonium salt is regenerated from solutions of the colour-base and $-base by the addition of hydrochloric acid. Cl,K1,O,Cl,BH,O requires C = 56-2 ; H = 5.5%). Cyaizidiii Chloride Pentamethyl Ether (V). I n order t o obtain good results in this preparation it is very necessary that the materials employed should be pure. Hydrogen chloride was passed for 1 hour through a solution of 2-hydroxy-4 5-dimethouybenzaldehyde (4-5 g.) and w-methosyacetoveratrone (5-2 g.) in ether (50 c.c.).The solution quickly became crimson and crystallisation of the product was induced by scratching after 30 minutes from the commencement. The tube containing the mixture and a dish containing solid potassium hydroxide were together covered by a bell-jar and after several hours the salt was collected washed with ether and dried (5.5 g.). The salt crystal-lises from alcohol containing a little hydrogen chloride in small, red necdles m. p. 152" which in mass exhibit an old-gold sheen, but give a chocolate-brown smear on paper (Found in material dried in a vacuum over phosphoric oxide and potassium hydroxide : C = 51.7 ; H = 5.9 ; C1 = 14.9. C,,,H,,B,Cl,HCl,2H20 requires C = 51.6; H = 5.6; C1 = 15.2%).The same dtchloride crystal-lised from a mixture of alcohol and concentrated aqueous hydro-chloric acid in slender needles m. p. 152" (Found C = 51.5; H = 5.5; C1 = 15.4%). From 776 aqueous hydrochloric acid the salt separates in long orange-brown needles which form a crystalline crust exhibiting a green reflex (Found in material dried in a vacuum C = 53-2 ; H = 6.0. C,,H,,O,C1,3H,O requires C = 53-7 ; H = 6.00/,). The substance is readily soluble in the simple c," 172 PRATT AND ROBINSON A SYNTHESIS OF alcohols to reddish-violet solutions the colour of which fades on dilution with water and can then be restored by the addition of a mineral acid. The ferrichloride crystallises from acetic acid in which it is very sparingly soluble in reddish-brown prismatic needles m.p. 196200' (decomp.) exhibiting a bronze lustre. The chloride is insoluble in chloroform but this derivative is moderately readily soluble and when the hot saturated solution is rapidly concentrated to one-quarter of its bulk the ferrichloride separates in microscopic needles exhibiting an intense green lustre. Cyanidin Chloride (VI). The foregoing pentamethyl ether (3.2 g.) and phenol (15 g.) were added to hydriodic acid (180 c.c.; d 1.7) and the mixture was boiled for 30 minutes in an atmosphere of carbon dioxide. Water (2 vols.) and much ether were added to the cooled solution and on standing glistening needles with a bright green reflex separated. The substance (1.8 g.) had properties identical with those of cyanidin iodide prepared by the demethylation of paeonidin chloride of natural origin (Willstatter and Nolan AnnaZen 1915 408 136).The iodide (3 g.) was thoroughly ground with aqueous sodium acetate the bluish-violet colour-base separated thoroughly washed, and heated to boiling with 3% aqueous hydrochloric acid (100 c.c.) in presence of a trace of silver and filtered 50 C.C. more 3% hydrochloric acid being used for washing. Concentrated hydro-chloric acid (50 c.c.) was added and on standing the dark red solution deposited the salt completely in masses of short reddish-brown prisms that had a green lustre (Found C = 52.5 ; H = 4.1. C1,HllO,C1,H,O requires C = 52.8; H = 343%). This product showed all the characteristic reactions of cyanidin chloride and a direct comparison with a specimen of the substance of natural origin disclosed no difference in properties of any kind.The behaviour on heating appearance of the crystals under the micro scope formation of colour-base and +-base solubilities in aqueous and alcoholic acid solutions colour of acid solutions absorption spectrum of the solution in ethyl alcohol and the reactions with ferric chloride sodium carbonate sodium acetate potassium acetate in alcoholic solution lead acetate and Fehling's solution were all examined. Willstatter and Everest (Zoc. cit.) state that cyanidin on oxidation with hydrogen peroxide yields a yellow crystalline product closely resembling a flavonol colouring matter. There is, however no clear evidence that quercetin can be obtained by the oxidation of cyanidin and furthermore it is remarkable that no chromone or chromonol derivative has yet been prepared by oxidising a benzopyrylium salt.We have made numerous experi PYRYLIUM SALTS OY ANTHOCYANIDIN TYPE. PART v. 173 ments with the object of achieving this transformation but any definite products isolated have been either carboxylic acids or cournarin derivatives. This investigation proceeds. w 3 4 5-Tetramethxyacetophenone (II).-Sodium (2.5 g.), granulated under toluene and washed with ether was suspended in ether (120 c.c.) and ethyl ccy-dimethoxyacetoacetate (20 8.) slowly added. When the formation of the sodio-derivative appeared to be complete an ethereal solution of trimethylgalloyl chloride (24.5 g.) was added in one portion and the mixture heated gently on the steam-bath for 8 hours.The product was isolated (34 9.) and shaken for 12 hours with 2.5% aqueous potassium hydroxide. The solution was boiled for 4 hours and the ketone isolated as in the case of w-methoxyacetoveratrone. The yield was 9 g. of a colourless oil b. p. 212"/15 mm. which solidified in contact with light petroleum. The substance crystallises from benzene-light petroleum in colourless needles m. p. 54" and closely resembles w-methoxyacetoveratrone (Found C = 60.0; H = 6.3. C,,H,,O, requires C = 60-0; H = 6.6%). The semicarbaxone crystalliser from aqueous alcohol in long colourless needles m. p. 158". 3-Metltoxy-6 ?-methylenedioxy-2-(3 4 5-trimethoxyphenyl)quinoE-ine crystallises from ethyl alcohol in colourless needles m.p. 159", and exhibits a violet fluorescence in alcoholic solution. Its salts, e.g. the sparingly soluble hydrochloride are yellow. The metho-svlphute is orange-yellow and it is evident from a comparison of this substance with the intensely coloured delphinidin chloride hexamethyl ether that the quinolinium and benzopyryhm nuclei function quite differently as chromophores. It may well be that the methoxyl groups are able to decentralise the cationic valency of the pyrylium nucleus and so produce changes of orbits of electrons owing to recurrent redistribution of the charge whilst on the other hand the powerfully basic quinolinium nucleus is able to ignore the claims of the weak auxochromes. We are thus led to anticipate that the aminophenylquinolinium salts will resemble tinctorially the related hydroxyphenylbenzopyrylium salts and it is hoped that an experimental test of this point will be made.Delphinidin Chloride Hexamethgl Ether (corresponding with VII). Hydrogen chloride was passed through an ice-cold solution of w 3 4 5-tetramethoxyacetophenone (4 g.) and 2-hydroxy-4 6-dimethoxybenzaldehyde (3 g.) in dry ether (50 c.c.) crystallisation of the product in crimson needles and prisms having a dark green reflex occurring after about 1 hour. Next day the salt (4 g . ) was collected and a further quantity (0.7 g.) was obtained from the ethereal mother-liquor. The substance crystallises from alcoho 174 A SYNTHESIS OF PYRYLIUM SALTS OF ANTHOCYANIDIN TYPE. containing a trace of hydrogen chloride in long red needles m.p. 163-164" (Found in material dried in a vacuum C = 58.5 ; H = 5.8. C21H,30,CI,0-5H20 requires C = 58.4; H = 5.6%). The substance exhibits a green lustre and is reddish-violet by transmitted light. It is readily soluble in the simple alcohols and moderately soluble in chloroform to a reddish-violet solution. The dark red colour of the solution in water rapidly fades and an almost colourless $-base is precipitated. Faintly acid solutions are also decolorised on great dilution but addition of acid restores the colour of the pyrylium salt. The ferrichloride crystalhes from glacial acetic acid in brownish-red needles which have a dark green appearance in mass. This derivative m. p. 169-170" is readily soluble in acetone chloroform or the simple alcohols.The sulphate crystallises from dilute sulphuric acid in slender red needles with green reflex m. p. 225" (decomp.). Delphinidin Chloride (VII). Delphinidin chloride hexamethyl ether (3-0 g.) was demethylated by means of a boiling mixture of hydriodic acid (180 c.c.; d 1.7) and phenol (15 g.) during 30 minutes a slow current of carbon dioxide being passed through the containing vessel. The cooled liquid deposited clusters of long pointed brown needles together with some squat prisms and these were collected washed with ether and dried (2.0 g.). The iodide was converted into chloride by treatment a t 60" with silver chloride in alcoholic solution in a silver-mirrored vessel. The filtered solution was mixed with an equal volume of concentrated hydrochloric acid and the amorphous precipitate so obtained allowed to remain when it slowly became resolved into a mass of microscopic needles.The substance was isolated and crystallised by solution in 5% hydrochloric acid and addition of 30% acid to the filtered solution so as to make the concentration of hydrochloric acid about 25%. The brown, crystalline mass was dried in a vacuum (Found C = 49.4; H = 4-0. C1,Hl10,Cl,1~5H20 requires C = 49.4; H = 3-8 ; H20 = 7.4y0). According to Willstatter and Weil (Annalen 1916 412, 178) delphinidin chloride crystallises from hydrochloric acid of 20% or greater concentrations with 1.5H20 which is completely lost in a vacuum. Our product did not behave in this way but the circumstance was an accident since when the material was powdered and again exposed to a vacuum it lost 7.6%.The anhydrous salt does not melt below 350". The hydrates containing 1H20 2H20 and 4H20 have been prepared by the methods devised by Willstatter and Weil in order to observe the crystalline forms, which were found to agree with the descriptions of these authors SYNTHESIS OF CERTAIN HIGHER ALIPHATIC COMPOUNDS. PART I. 175 The absorption spectrum of an alcoholic solution of the chloride, the formation of the +base the behaviour of aqueous and acid solutions on shaking with ether ethyl acetate and isoamyl alcohol, the reactions with ferric chloride in aqueous and alcoholic solutions and with sodium carbonate sodium bisulphite lead acetate and Fehling’s solution were all examined with results identical with those described in the case of delphinidin chloride of natural origin by Willstatter and Mieg (AnnaZen 1915 408 61) and Willstatter and Weil (Zoc. cit.). We were not able to make a direct comparison, but the properties of delphinidin chloride are so characteristic and have been recorded in such detail that we can entertain no doubt as to the identity of the synthetical product with that obtained by the hydrolysis of the pigments of the wild purple larkspur and the blue-black pansy. One of us (D. D. P.) desires to thank the Carnegie Trust for t3he Universities of Scotland for a Fellowship which has enabled him to take part in this investigation. THE UNIVERSITY MANCHESTER. [Received November 3 ~ d 1924.

ISSN:0368-1645    

DOI:10.1039/CT9252700166

出版商:RSC    

年代:1925

数据来源: RSC

摘要:

SYNTHESIS OF CERTAIN HIGHER ALIPHATIC COMPOUNDS. PART I. 175 XXVIL-Synthesis of certain Higher Aliphatic Cmn-pounds. Part I . A S'ynthesis of Lactarinic Acid and of Oleic Acid. By GERTRUDE MAUD ROBINSON and ROBERT ROBIK'SON. THIS investigation originated in a desire to develop methods which could be applied to the synthesis of the naturally occurring unsatur-ated fatty acids and attention was concentrated in the first place on attempts to synthesise oleic acid. An examination of the literature shows that this acid has been obtained from 10-ketostearic acid,* CH,*[CH,],*CO*[CH,],*CO,H by reduction to hydroxystearic acid followed by conversion to iodostearic acid and treatment with alcoholic potassium hydroxide (see p. 179). It therefore became an object to devise a process for the preparation of acids of the form R*[CH,],*CO*[CH,],*CO,H which should be applicable t o a case such that R*[CH,],I cannot be readily converted into an organo-zinc or magnesium derivative.After numerous trials in other directions, it was found that ethyl sodio-n-heptylmalonate and 9-carbethoxy-nonoyl chloride condensed in ethereal solution to a product which * Tho carboxyl group of stearic acid is numbered 1 in this communication This syste:n in order to avoid confusion with the Geneva nomenclature. has been frequently adopted in recent literature 156 ROBINSON AND ROBINSON SYNTHESIS OF gave a very small yield of 10-ketostearic acid on prolonged hydrolysis with boiling 1 yo aqueous oxalic acid. A considerable improvement was effected by starting with ethyl acetoacetate instead of ethyl malonate.Ethyl sodio-2-acetylnonoate and 9-carbethoxynonoyl chloride were brought into reaction in ether and the resulting ester, CH,*[CH,],*CAc( CO,Et)*CO*[ CH,] ,*CO,Et was cautiously hydro-lysed at first by cold dilute alkali then by boiling dilute sulphuric acid and finally by boiling dilute aqueous sodium hydroxide. The aparingly soluble crystalline sodium salt of 10-ketostearic acid separated on cooling the solution. This acid melts at 83" and the product of the action of sulphuric acid and water on stearolic acid, after a wasteful process of purification melts at the same temper-ature alone or mixed with the synthetic specimen. It is probable that the isomeride accompanying 10-ketostearic acid in the crude material derived from stearolic acid is 9-ketostearic acid and we are engaged in the preparation of this substance in order to determine the proportions in which the acetylenic bond is hydrated in the two possible directions.The synthesis of oleic acid by way of 10-keto-stearic acid and 10-iodostearic acid affords a proof that the double bond is in the position A9:10 or AIO'I1 and in order to eliminate the latter alternative we are engaged in an attempt to synthesise stearolic acid. We have found that this acid may be reduced to oleic acid by means of zinc dust and hydrochloric acid in presence of titanous chloride in acetic acid solution. Elaidic and stearic acids are not produced under the conditions described (p. 177) and the reaction indicates that oleic acid has the cis-configuration.The addition of hydrogen iodide to stearolic acid has been previously shown to lead to isomeric iodoelaidic acids which can be transformed into elaidic acid (Arnaud and Posternak C m p t . rend. 1910 150 1130, 1525). In the course of investigations on the constituents of certain fungi, Bougault and Charaux found that several species of Lactarius contained a ketostearic acid termed lactarinic acid in the free state (Compt. rend. 1911 153 572 880). The results obtained by applying the Beckmann transformation to the oxime of lactarinic acid showed that the substance must be 6-ketostlearic acid and we have now confirmed this conclusion by synthesis. Ethyl sodio-2-acetyl-n-tridecoate and 5-carbethoxyvaleryl chloride react in ethereal solution so as to produce the ester CH,*[CH2],,~CAc(C0,Et)~CO*[CH2],*C0,Et, which by graduated hydrolysis yields lactarinic acid, CH,*[CH,]ll-CO*[CH,]4*C02H.We are greatly indebted to &ofessor Bougault for a specimen of the acid of natural origin and a careful comparison proved the identit CERTAIN HIGHER ALIPHATIC COMPOUNDS. PART I. 177 of this with the synthetical product. At the suggestion of Professor H. S. Raper we have also synthesised 4-ketopalmitic acid in order to render possible a direct comparison with a substance prepared by the oxidation of palmitic acid. I n this case ethyl sodio-2-acetyl-n-tridecoate and 3-carbomethoxypropionyl chloride gave the ester CH,-[CH,]1,*CAc(C02Et)CO*[CH,]2*C0,Me and by hydrolysis the desired keto-acid CH,*[CH,],,*CO*[CH,]~*CO,H.E x P E R I M E N T A L . Reduction of Xtearolic Acid to Oleic Acid .-Hydrochloric acid (50 C.C. of 40%) was slowly added to a gently boiling mixture of acetic acid (30 g.) aqueous titanous chloride (10 g. of 15%) stearolic acid (3 g.) and zinc dust (10 g.) contained in a flask closed by a tube bearing a Bunsen valve. After 2 hours zinc dust (5 g.) and acetic acid (20 c.c.) were added and the process was completed by boiling for 2 hours. The product was mixed with ether the separated ethereal solution well washed with water and the acid contained converted into its barium salt (3.5 g.) which was twice crystallised from a mixture of benzene (8 vols.) ethyl alcohol (1 vol.) and a trace of water. The free oleic acid obtained from the barium salt and hot dilute hydrochloric acid was dried in light petroleum (b.p. 4 0 4 5 " ) with anhydrous sodium sulphate and the solvent removed. The residue consisting of the pure acid crystallised on cooling as a glassy mass which froze at 12-5" in one experiment and at 13" in another. These freezing points were taken with the thermometer immersed in the liquid and the specimen freezing a t 13" froze a t the same temperature when mixed with a specimen of pure oleic acid prepared from olive oil for which me are indebted to Professor A. Lapworth. The characteristic dimorphism exhibited by oleie acid has been described by Iiirchner (2. physikaE. Chem., 1913 79 789) and when the acid freezing at 13" was maintained a t about 12" the nuclei of the new modification gradually formed and closely resembled in appearance under the lens the photographs reproduced in the memoir quoted above.The transformed material melted just above 16". When the acid dissolved in 300 times its weight of water and one-third of its weight of potassium hydroxide was oxidised at 0" by the gradual addition of 0.5h7-potassium permanganate dihydroxystearic acid was produced in almost theoretical amount; it was best isolated by filtration after the passage of sulphur dioxide. The substance crystallised from alcohol-benzene melted at 132" alone or mixed with a specimen prepared from oleic acid from olive oil. The melting point 136" given in the literature for this acid is too high. 9-C'arEethoxynona?tilide.-Ethyl hydrogen sebacate (22 g . ) (Grii 178 ROBINSON AND ROBINSON SYNTHESIS OF and Whfh Bey.1922 55 2207) was heated on the steam-bath for 3 hours with thionyl chloride * (66 g.) the thionyl chloride removed completely by distillation under reduced pressure and exposure of the residue to a vacuum and 9-carbethoxynonoyl chloride thus obtained in good yield treated wit'h an excess of aniline. The aizilide crystallised from light pettroleum containing a little benzene in colourless needles m. p. 63" (Found C = 70.9; H = 8.7. C1,H,,03N requires C = 70.8; H = 8.8%). 10-Ketostearic Acid.-The condensation of ethyl sodio-n-heptj-1-malonate with 9-carbethoxynonoyl chloride was carried out like that in the case of the related derivative of acetoacetic acid. The product was an oil which on hydrolysis by alkali gave heptylmalonic and sebacic acids but no ketostearic acid.Dilute sulphuric acid gave a similar result but 1% aqueous oxalic acid caused partial hydrolysis in the desired direction and a very small yield of 10-keto-stearic acid m. p. 77" could be isolated after boiling during a week. The process was obviously unsatisfactory and was abandoned in favour of tlhe following kethod. Sodium (1.2 g.) was granulated under toluene washed with ether, suspended in ether (75 c.c.) and a solution of ethyl 2-acetylnonoate (11-5 g.) (Jourdan Annalen 1879 200 105) in ether (75 c.c.) gradually added. The clear solution of the sodio-derivative obtained by gentle heating was cooled in melting ice and treated with 9-carbethoxynonoyl chloride (12.5 g . ) in ether (20 c.c.). After 1 hour the mixture was boiled for 10 minutes cooled washed with water and the ether evaporated.The residue was shaken with 5% aqueous sodium hydroxide (200 c.c.) for 2 days and then after acidification with acetic acid collected again by means of ether, boiled during 24 hours with 6% sulphuric acid (300 c.c.) and the mixture steam-distilled ; the oil in the distillate was methyl n-octyl ketone (Jourdan Zoc. cit.). The residue in the flask was once more collected by means of ether and boiled during 1.5 hours with 5% aqueous sodium hydroxide (100 c.c.). On cooling the gelatinous precipitate first formed rapidly changed to colourless leaflets, m. p. 212". The acid obtained from this salt crystallised from alcohol and from light petroleum in colourless plates m.p. 83" and a t the same temperature when rnised with 10-ketostearic acid derived from stearolic acid as described below. The two specimens were carefully compared and no differences could be discerned. Stearolic acid was dissolved in concentrated sulphuric acid (6 parts) as recommended by Baruch (Ber. 1884 27 174) but water was not added after 12 hours the solution being filtered by glass wool chloride and 1% of sulphur. * Purified by distillation after boiling under reflux with 1% of aluminiu CERTAIN ICIGIIER ALIPHATIC COMPOUNDS. PART I. 179 and kept in an open vessel. The crust which formed at the surface was removed from time to time drained on porous porcelain, crystallised from alcohol converted into sodium salt which was also crystallised from alcohol finally the recovered acid was crystallised twice from light petroleum and twice from benzene.The product melted at 83" whereas the crude acid melts at about 72" and the highest recorded melting point is 76". 10-Hydroxystearic acid prepared in theoretical yield by the reduction of pure sodium 10-ketostearate in dry alcohol by means of sodium melts at 84.5". This acid yields 10-iodostearic acid by the action of phosphorus fri-iodide and water and Arnaud and Bosternak (Cmpt. rend., 1910,150,1525) have carefully examined the products of the action of alcoholic potassium hydroxide on this iodostearic acid a reaction first investigated by Saytzeff ( J . pr. Chem. 1887 [ii] 35,387). The former authors showed that oleic acid hydroxystearic acid arid isomeric elaidic acids can be isolated.EthyE 2 - Acetyl-n-tridecoate CH,*[CH,] ,,*CHAc*CO,Et .-12*2 Grams of an oil b. p. 185"/17 mm. were obtained according to the usual method employing sodium (1.4 g.) alcohol (17.5 g.) ethyl acetoacetate (11.8 g.) n-undecyl iodide (17 g.) ; the time of reaction was 3-5 hours (Found C = 72.1 ; H = 11.1. C,,H,,O requires 6-Ketostearic Acid (Lactnrinic Acid) .-Ethyl hydrogen adipate, prepared by a method analogous to that employed by Griin and Wirth (Zoc. cit.) in the semi-hydrolysis of diethyl sebacate was converted into the acid chloride by means of pure thionyl chloride. 5-Carbethoxyvaleryl chloride (8.5 9.) dissolved in ether (10 c.c.) was added to a solution of ethyl sodio-2-acetyl-n-tridecoate (136 g.) in ether (75 c.c.) at 0" ; after remaining 4 hour at room temperature, the mixture was boiled under reflux for 15 minutes.The washed and isolated product was shaken for 16 hours with 5% aqueous sodium hydroxide (300 c.c.) collected as in the previous example, and boiled with 5% sulphuric acid (600 c.c.) for 24 hours. Steam distillation separated some methyl n-dodecyl ketone m. p. 33-34" (Krafft Eer. 1882 15 1708) and the residue in the flask was collected and heated for 4-5 hours with boiling 5% aqueous sodium hydroxide (200 c.c.). The sodium salt (4-2 g.) which crystallised on cooling was collected and the acid isolated and crystallised from alcohol. The colourless plates melted at 87" alone or mixed with an authentic specimen of lactarinic acid (Pound C = 72.7; H = 11.3. Calc.for C1BH34:3 C = 72.5; H = 11.4%). The o x i m m. p. 59-61 crystallised from light petroleum in microscopic needles and was transformed by concentrated sulphuric acid at 100" into an amide crystallising from alcohol in colourless C == 71.8; H = 11.3%) 180 SYNTHESIS OF CERTAIN HIGHER ALIPHATIC COMPOUNDS. PART I. needles m. p. 104". These m. pt's. agree with those given by Bougault and Charaux (Zoc. cit.). 3 - Carbomethoxypropionanilide CO,Me*CH,*CH,*CO*NHPh .-Methyl hydrogen succinate being a solid m. p. 58" was used in preference to the corresponding ethyl derivative in the synthesis of 4-ketopalmitic acid. Succinic anhydride conveniently obtained by the action of thionyl chloride on the acid was converted into the semi-ester by the method of Bone Sprankling and Sudborough (J.1904 85 530). 3-Carbomethoxy~ro,/r,ionyl chloride derived from the acid by the action of thionyl chloride is a colourless liquid, b. p. 93"/18 mm. and reacts with aniline with formation of 3-carbo-methoxypropionanilide which crystallises from light petroleum-benzene as also from ether in colourless needles m. p. 97-99' (Found C = 63-8 ; H = 6.4. Calc. for C1lH,,O,N C = 63.7 ; H = 6.3%). The same substance has been prepared by the action of methyl alcohol and hydrogen chloride on succinanil (van der Meulen Rec. trav. chim. 1896 15 341 ; Eioogewerth and van Dorp, ibid. 1898,1'7,200). 4-Ketopalmitic Acid.-A solution of 3-carbomethoxypropionyl chloride (ti g.) in ether (30 c.c.) was added to the sodio-derivative from ethyl 2-acetyl-n-tridecoate (1 1 g.) and granulated sodium (0.9 g.) in ether (320 c.c.).The mixture was cooled in ice-water, kept over-night and boiled under reflux for 8 hour. The washed and isolated product was hydrolysed by shaking for 6 hours with 5% potassium hydroxide (300 c.c.) boiling for 30 hours with 5% sulphuric acid (250 c.c.) and for 3 hours with 5% potassium hydroxide. The potassium salt did not separate on cooling and, on acidification of the solution 5-1 g. of almost pure 4-ketopalmitic acid were obtained. The substance crystallises from light petroleum in colourless clusters of waxy lanceolate plates m. p. 91-92" (Found C = 71.3 ; H = 11.0. C,,H,,O requires C = 71.1 ; H = 11.1 %). The oxime is readily soluble in most organic solvents and crystallises from light petroleum in colourless needles m.p. 54". We desire to express our thanks to the Food Inves-bigation Board for grants which have eiiabled one of us to take part in this investigation. TIIE UNIVERSITY MANCHESTER. [Received November loth 1924. SYNTHESIS OF CERTAIN HIGHER ALIPHATIC COMPOUNDS. PART I. 175 XXVIL-Synthesis of certain Higher Aliphatic Cmn-pounds. Part I . A S'ynthesis of Lactarinic Acid and of Oleic Acid. By GERTRUDE MAUD ROBINSON and ROBERT ROBIK'SON. THIS investigation originated in a desire to develop methods which could be applied to the synthesis of the naturally occurring unsatur-ated fatty acids and attention was concentrated in the first place on attempts to synthesise oleic acid. An examination of the literature shows that this acid has been obtained from 10-ketostearic acid,* CH,*[CH,],*CO*[CH,],*CO,H by reduction to hydroxystearic acid followed by conversion to iodostearic acid and treatment with alcoholic potassium hydroxide (see p.179). It therefore became an object to devise a process for the preparation of acids of the form R*[CH,],*CO*[CH,],*CO,H which should be applicable t o a case such that R*[CH,],I cannot be readily converted into an organo-zinc or magnesium derivative. After numerous trials in other directions, it was found that ethyl sodio-n-heptylmalonate and 9-carbethoxy-nonoyl chloride condensed in ethereal solution to a product which * Tho carboxyl group of stearic acid is numbered 1 in this communication This syste:n in order to avoid confusion with the Geneva nomenclature.has been frequently adopted in recent literature 156 ROBINSON AND ROBINSON SYNTHESIS OF gave a very small yield of 10-ketostearic acid on prolonged hydrolysis with boiling 1 yo aqueous oxalic acid. A considerable improvement was effected by starting with ethyl acetoacetate instead of ethyl malonate. Ethyl sodio-2-acetylnonoate and 9-carbethoxynonoyl chloride were brought into reaction in ether and the resulting ester, CH,*[CH,],*CAc( CO,Et)*CO*[ CH,] ,*CO,Et was cautiously hydro-lysed at first by cold dilute alkali then by boiling dilute sulphuric acid and finally by boiling dilute aqueous sodium hydroxide. The aparingly soluble crystalline sodium salt of 10-ketostearic acid separated on cooling the solution. This acid melts at 83" and the product of the action of sulphuric acid and water on stearolic acid, after a wasteful process of purification melts at the same temper-ature alone or mixed with the synthetic specimen.It is probable that the isomeride accompanying 10-ketostearic acid in the crude material derived from stearolic acid is 9-ketostearic acid and we are engaged in the preparation of this substance in order to determine the proportions in which the acetylenic bond is hydrated in the two possible directions. The synthesis of oleic acid by way of 10-keto-stearic acid and 10-iodostearic acid affords a proof that the double bond is in the position A9:10 or AIO'I1 and in order to eliminate the latter alternative we are engaged in an attempt to synthesise stearolic acid. We have found that this acid may be reduced to oleic acid by means of zinc dust and hydrochloric acid in presence of titanous chloride in acetic acid solution.Elaidic and stearic acids are not produced under the conditions described (p. 177) and the reaction indicates that oleic acid has the cis-configuration. The addition of hydrogen iodide to stearolic acid has been previously shown to lead to isomeric iodoelaidic acids which can be transformed into elaidic acid (Arnaud and Posternak C m p t . rend. 1910 150 1130, 1525). In the course of investigations on the constituents of certain fungi, Bougault and Charaux found that several species of Lactarius contained a ketostearic acid termed lactarinic acid in the free state (Compt. rend. 1911 153 572 880). The results obtained by applying the Beckmann transformation to the oxime of lactarinic acid showed that the substance must be 6-ketostlearic acid and we have now confirmed this conclusion by synthesis.Ethyl sodio-2-acetyl-n-tridecoate and 5-carbethoxyvaleryl chloride react in ethereal solution so as to produce the ester CH,*[CH2],,~CAc(C0,Et)~CO*[CH2],*C0,Et, which by graduated hydrolysis yields lactarinic acid, CH,*[CH,]ll-CO*[CH,]4*C02H. We are greatly indebted to &ofessor Bougault for a specimen of the acid of natural origin and a careful comparison proved the identit CERTAIN HIGHER ALIPHATIC COMPOUNDS. PART I. 177 of this with the synthetical product. At the suggestion of Professor H. S. Raper we have also synthesised 4-ketopalmitic acid in order to render possible a direct comparison with a substance prepared by the oxidation of palmitic acid.I n this case ethyl sodio-2-acetyl-n-tridecoate and 3-carbomethoxypropionyl chloride gave the ester CH,-[CH,]1,*CAc(C02Et)CO*[CH,]2*C0,Me and by hydrolysis the desired keto-acid CH,*[CH,],,*CO*[CH,]~*CO,H. E x P E R I M E N T A L . Reduction of Xtearolic Acid to Oleic Acid .-Hydrochloric acid (50 C.C. of 40%) was slowly added to a gently boiling mixture of acetic acid (30 g.) aqueous titanous chloride (10 g. of 15%) stearolic acid (3 g.) and zinc dust (10 g.) contained in a flask closed by a tube bearing a Bunsen valve. After 2 hours zinc dust (5 g.) and acetic acid (20 c.c.) were added and the process was completed by boiling for 2 hours. The product was mixed with ether the separated ethereal solution well washed with water and the acid contained converted into its barium salt (3.5 g.) which was twice crystallised from a mixture of benzene (8 vols.) ethyl alcohol (1 vol.) and a trace of water.The free oleic acid obtained from the barium salt and hot dilute hydrochloric acid was dried in light petroleum (b. p. 4 0 4 5 " ) with anhydrous sodium sulphate and the solvent removed. The residue consisting of the pure acid crystallised on cooling as a glassy mass which froze at 12-5" in one experiment and at 13" in another. These freezing points were taken with the thermometer immersed in the liquid and the specimen freezing a t 13" froze a t the same temperature when mixed with a specimen of pure oleic acid prepared from olive oil for which me are indebted to Professor A.Lapworth. The characteristic dimorphism exhibited by oleie acid has been described by Iiirchner (2. physikaE. Chem., 1913 79 789) and when the acid freezing at 13" was maintained a t about 12" the nuclei of the new modification gradually formed and closely resembled in appearance under the lens the photographs reproduced in the memoir quoted above. The transformed material melted just above 16". When the acid dissolved in 300 times its weight of water and one-third of its weight of potassium hydroxide was oxidised at 0" by the gradual addition of 0.5h7-potassium permanganate dihydroxystearic acid was produced in almost theoretical amount; it was best isolated by filtration after the passage of sulphur dioxide. The substance crystallised from alcohol-benzene melted at 132" alone or mixed with a specimen prepared from oleic acid from olive oil.The melting point 136" given in the literature for this acid is too high. 9-C'arEethoxynona?tilide.-Ethyl hydrogen sebacate (22 g . ) (Grii 178 ROBINSON AND ROBINSON SYNTHESIS OF and Whfh Bey. 1922 55 2207) was heated on the steam-bath for 3 hours with thionyl chloride * (66 g.) the thionyl chloride removed completely by distillation under reduced pressure and exposure of the residue to a vacuum and 9-carbethoxynonoyl chloride thus obtained in good yield treated wit'h an excess of aniline. The aizilide crystallised from light pettroleum containing a little benzene in colourless needles m. p. 63" (Found C = 70.9; H = 8.7. C1,H,,03N requires C = 70.8; H = 8.8%).10-Ketostearic Acid.-The condensation of ethyl sodio-n-heptj-1-malonate with 9-carbethoxynonoyl chloride was carried out like that in the case of the related derivative of acetoacetic acid. The product was an oil which on hydrolysis by alkali gave heptylmalonic and sebacic acids but no ketostearic acid. Dilute sulphuric acid gave a similar result but 1% aqueous oxalic acid caused partial hydrolysis in the desired direction and a very small yield of 10-keto-stearic acid m. p. 77" could be isolated after boiling during a week. The process was obviously unsatisfactory and was abandoned in favour of tlhe following kethod. Sodium (1.2 g.) was granulated under toluene washed with ether, suspended in ether (75 c.c.) and a solution of ethyl 2-acetylnonoate (11-5 g.) (Jourdan Annalen 1879 200 105) in ether (75 c.c.) gradually added.The clear solution of the sodio-derivative obtained by gentle heating was cooled in melting ice and treated with 9-carbethoxynonoyl chloride (12.5 g . ) in ether (20 c.c.). After 1 hour the mixture was boiled for 10 minutes cooled washed with water and the ether evaporated. The residue was shaken with 5% aqueous sodium hydroxide (200 c.c.) for 2 days and then after acidification with acetic acid collected again by means of ether, boiled during 24 hours with 6% sulphuric acid (300 c.c.) and the mixture steam-distilled ; the oil in the distillate was methyl n-octyl ketone (Jourdan Zoc. cit.). The residue in the flask was once more collected by means of ether and boiled during 1.5 hours with 5% aqueous sodium hydroxide (100 c.c.).On cooling the gelatinous precipitate first formed rapidly changed to colourless leaflets, m. p. 212". The acid obtained from this salt crystallised from alcohol and from light petroleum in colourless plates m. p. 83" and a t the same temperature when rnised with 10-ketostearic acid derived from stearolic acid as described below. The two specimens were carefully compared and no differences could be discerned. Stearolic acid was dissolved in concentrated sulphuric acid (6 parts) as recommended by Baruch (Ber. 1884 27 174) but water was not added after 12 hours the solution being filtered by glass wool chloride and 1% of sulphur. * Purified by distillation after boiling under reflux with 1% of aluminiu CERTAIN ICIGIIER ALIPHATIC COMPOUNDS.PART I. 179 and kept in an open vessel. The crust which formed at the surface was removed from time to time drained on porous porcelain, crystallised from alcohol converted into sodium salt which was also crystallised from alcohol finally the recovered acid was crystallised twice from light petroleum and twice from benzene. The product melted at 83" whereas the crude acid melts at about 72" and the highest recorded melting point is 76". 10-Hydroxystearic acid prepared in theoretical yield by the reduction of pure sodium 10-ketostearate in dry alcohol by means of sodium melts at 84.5". This acid yields 10-iodostearic acid by the action of phosphorus fri-iodide and water and Arnaud and Bosternak (Cmpt. rend., 1910,150,1525) have carefully examined the products of the action of alcoholic potassium hydroxide on this iodostearic acid a reaction first investigated by Saytzeff ( J .pr. Chem. 1887 [ii] 35,387). The former authors showed that oleic acid hydroxystearic acid arid isomeric elaidic acids can be isolated. EthyE 2 - Acetyl-n-tridecoate CH,*[CH,] ,,*CHAc*CO,Et .-12*2 Grams of an oil b. p. 185"/17 mm. were obtained according to the usual method employing sodium (1.4 g.) alcohol (17.5 g.) ethyl acetoacetate (11.8 g.) n-undecyl iodide (17 g.) ; the time of reaction was 3-5 hours (Found C = 72.1 ; H = 11.1. C,,H,,O requires 6-Ketostearic Acid (Lactnrinic Acid) .-Ethyl hydrogen adipate, prepared by a method analogous to that employed by Griin and Wirth (Zoc. cit.) in the semi-hydrolysis of diethyl sebacate was converted into the acid chloride by means of pure thionyl chloride.5-Carbethoxyvaleryl chloride (8.5 9.) dissolved in ether (10 c.c.) was added to a solution of ethyl sodio-2-acetyl-n-tridecoate (136 g.) in ether (75 c.c.) at 0" ; after remaining 4 hour at room temperature, the mixture was boiled under reflux for 15 minutes. The washed and isolated product was shaken for 16 hours with 5% aqueous sodium hydroxide (300 c.c.) collected as in the previous example, and boiled with 5% sulphuric acid (600 c.c.) for 24 hours. Steam distillation separated some methyl n-dodecyl ketone m. p. 33-34" (Krafft Eer. 1882 15 1708) and the residue in the flask was collected and heated for 4-5 hours with boiling 5% aqueous sodium hydroxide (200 c.c.).The sodium salt (4-2 g.) which crystallised on cooling was collected and the acid isolated and crystallised from alcohol. The colourless plates melted at 87" alone or mixed with an authentic specimen of lactarinic acid (Pound C = 72.7; H = 11.3. Calc. for C1BH34:3 C = 72.5; H = 11.4%). The o x i m m. p. 59-61 crystallised from light petroleum in microscopic needles and was transformed by concentrated sulphuric acid at 100" into an amide crystallising from alcohol in colourless C == 71.8; H = 11.3%) 180 SYNTHESIS OF CERTAIN HIGHER ALIPHATIC COMPOUNDS. PART I. needles m. p. 104". These m. pt's. agree with those given by Bougault and Charaux (Zoc. cit.). 3 - Carbomethoxypropionanilide CO,Me*CH,*CH,*CO*NHPh .-Methyl hydrogen succinate being a solid m. p. 58" was used in preference to the corresponding ethyl derivative in the synthesis of 4-ketopalmitic acid.Succinic anhydride conveniently obtained by the action of thionyl chloride on the acid was converted into the semi-ester by the method of Bone Sprankling and Sudborough (J. 1904 85 530). 3-Carbomethoxy~ro,/r,ionyl chloride derived from the acid by the action of thionyl chloride is a colourless liquid, b. p. 93"/18 mm. and reacts with aniline with formation of 3-carbo-methoxypropionanilide which crystallises from light petroleum-benzene as also from ether in colourless needles m. p. 97-99' (Found C = 63-8 ; H = 6.4. Calc. for C1lH,,O,N C = 63.7 ; H = 6.3%). The same substance has been prepared by the action of methyl alcohol and hydrogen chloride on succinanil (van der Meulen Rec.trav. chim. 1896 15 341 ; Eioogewerth and van Dorp, ibid. 1898,1'7,200). 4-Ketopalmitic Acid.-A solution of 3-carbomethoxypropionyl chloride (ti g.) in ether (30 c.c.) was added to the sodio-derivative from ethyl 2-acetyl-n-tridecoate (1 1 g.) and granulated sodium (0.9 g.) in ether (320 c.c.). The mixture was cooled in ice-water, kept over-night and boiled under reflux for 8 hour. The washed and isolated product was hydrolysed by shaking for 6 hours with 5% potassium hydroxide (300 c.c.) boiling for 30 hours with 5% sulphuric acid (250 c.c.) and for 3 hours with 5% potassium hydroxide. The potassium salt did not separate on cooling and, on acidification of the solution 5-1 g. of almost pure 4-ketopalmitic acid were obtained. The substance crystallises from light petroleum in colourless clusters of waxy lanceolate plates m. p. 91-92" (Found C = 71.3 ; H = 11.0. C,,H,,O requires C = 71.1 ; H = 11.1 %). The oxime is readily soluble in most organic solvents and crystallises from light petroleum in colourless needles m. p. 54". We desire to express our thanks to the Food Inves-bigation Board for grants which have eiiabled one of us to take part in this investigation. TIIE UNIVERSITY MANCHESTER. [Received November loth 1924.

ISSN:0368-1645    

DOI:10.1039/CT9252700175

出版商:RSC    

年代:1925

数据来源: RSC

摘要:

KALBF AND ROBINSON A SYNTHESIS OF MYRICETIN ETC. 181 XXVIIL-A Synthesis of Myricetin and of a Galangin Monomethyl Ether Occurring in Galanga Root. By JAN IZALFF and ROBERT ROBINSON. ALLAN and ROBINSON (J. 1924 125 2192) have described an extremely simple method of preparation of 7-hydroxy-3-methoxy-flavone by hydrolysis of the product of the action of benzoic anhydride and sodium benzoate on o-methoxyresacetophenone a t 180-185". On applying the reaction to w-methoxyphloraceto-phenone (Slater and Stephen J. 1920 117 316) we have now obtained an excellent yield of 5 7-dihyciroxy-3-methoxyflavone (I), which is identical with the galangin monomethyl ether isolated from galanga root the rhizome of Alpinia officinarum (Hance) by Testoni (Gazzetla 1900 30 ii 327). The formation of phloro-glucinol and benzoic acid by the aerial oxidation of an alkaline solution of the substance was observed by A.G. Perkin and Allison (J. 1902 81 472) and led to the suggestion that it is galangin 3-monomethyl ether. This conclusion is now confirmed by syn-thesis and the occurrence of the methyl group in this position in the molecule of a naturally occurring flavonol is of interest because there is reason to believe that certain of the anthocyanidins are similarly constituted in respect of this structural detail. The attractive view that the anthocyanin and anthoxanthin pigments are intimately and genetically related derives support from the accumulation of such coincidences. Galangin itself is obtained by demethylation of the methyl ether and this flavonol has been previously synthesised by v.Kostanecki and Tambor (Ber. 1899, 32 2260). 0 0 Myricetin was first isolated by A. G. Perkin and Hummel (J., 1896 69 1287) from the bark of Myrica nagi (Thunb) and as a result of this and subsequent investigations (Perkin J. 1902 81, 204; 1911 99 1721 ; Perkin and Phipps J. 1904 85 62) has been regarded as 3 5 7 3' 4' 5' :-hexahydroxyflavone (I1 with H in place of Me). Myricetin is somewhat widely distributed in nature and it is the flavonol which should yield a delphinidin salt on reduction in acid solution. The synthesis of the colouring matter is a further example of the new and convenient method of prepara-tion of the flavonols. o-Methoxyphloroacetophenone was heate 182 KALFF AND ROBINSON A SYNTIIESIS OF MYRICETIN with trimethylgallic anhydride and sodium trimethylgallate and the product hydrolysed.The 5 7-dihydroxy-3 3' 4' 5'-tetra-methoxyflavone (11) thus obtained yields myricetin on demethyl-ation. Phloroglucinol is converted in this manner into mvyricetin through two isolated intermediate stages only and the synthesis is also available as a preparative method. E x P E R I AT E N T A L. Galangin 3-Monomethyl Ether (I).-A mixture of w-methoxy-phloroacetophenone (5 g . ) sodium benzoate (6 g.) and benzoic anhydride (15 g.) was heated (oil-bath at MOO) during 8 hours, after which alcohol (75 c.c,) was added to the dark red semi-solid mass and potassium hydroxide (8.5 g.) in water (10 c.c.) gradually introduced to the boiling solution. After refluxing for Q hour the greater part of the alcohol was evaporated the residue dissolved in water and the flavonol precipitated as a brown powder by saturating the liquid with carbon dioxide collected washed and dried (6.5 g.).The substance was purified through its diacetyl derivative prepared by the action of boiling acetic anhydride during 2 hours. After two crystallisations from alcohol (charcoal) the substance was obtained in long very pale yellow needles m. p. 175-176" (Found : C = 65.3; H = 4.4. C,,H,,O requires C = 65-2; H = 4.4 yo). Testoni (Gazzeita 1900 30 ii 327) states that the diacetate derived from the galangin monomethyl ether from galanga root melts a t 175-176'. The diacetylgalangin methyl ether was hydrolysed by means of an excess of 10% aqueous potassium hydroxide on the steam-bath.The phenol precipitated by hydrochloric acid may be crystallised from alcohol acetic acid or ethyl acetate in rectan-gular yellow plates m. p. 299" soluble in dilute aqueous potassium hydroxide to an intense yellow solution (sodium salt yellow needles) and in sulphuric acid to a yellow solution exhibiting green fluor-escence (Found C = 67.2; H = 4.4. CI6Hl2O5 requires C = 67.6; 13 = 4.3%). The properties of this substance agree with those ascribed to natural galangin monomethyl ether by Testoni (Zoc. cit.) and the identity was proved by the fact that the melting point of the synthetical material was not lowered by admixture with the natural product for a specimen of which we are greatly indebted to Professor A.G. Perkin. Demethylation by means of boiling hydriodic acid (d 1.'7) mixed with a quarter of its weight of acetic anhydride during 40 minutes resulted in the formation of galangin m. p. 214-215" after crystallisation from alcohol. Myricetin 3 3' 4' 5I-Tetramethyl Ether (II).-Pyridine (52 g.) was gradually added to a solution of trimethylgalloyl chloride (35 g.) (Perkin and Weizmann J. 1906 89 1655) in ether (250 c.c. AND OF A GALANGIN MONOMETHYL ETHER ETC. 183 and after 2 hours ice and then water was gradually introduced, and the trimethyl gallic anhydride which is sparingly soluble in ether collected washed with dilute aqueous sodium carbonate solution and dried (yield 75%). This product melted a t 159" (corr.) and was employed without further purification (Fischer and Freudenberg Ber.1913 46 1129 give 160-161" [corr.] as the m. p. of the pure substance). A mixture of trimethylgallic anhydride (23 g.)? sodium trimethylgallate (10 g.) and o-methoxyphloro-acetophenone (4.5 g.) was heatcd a t 175" for 3 hours. The mixture was a t first completely fluid but as the reaction proceeded it became a dark red paste. As in the previous example the flavonol was isolated by treatment of the crude product with an alcoholic solution of potassium hydroxide (8 g.) and precipitation of the phenolic material by means of carbon dioxide after removal of the alcohol and solution of the residue in water. The crude material (8.2 g.) was acetylated by boiling with an excess of acetic anhydride and the derivative crystallised from alcohol.3 3' 4' 5'-Tetramethylmyricetin diacetate was obtained in long pale yellow needles m. p. 159" (corr.) (Found C = 60.3; H = 4.9. C23H2a0, requires C = 60.2; H = 4.9%). On hydro-lysis by means of boiling concentrated hydrochloric acid this derivative yields myricetin tetramethyl ether which crystallises from alcohol in thin glistening pale yellow plates m. p. 276-277-5" (Found C = 60.6 ; H = 4.8. CI9Hl8O8 requires C = 60.9 ; H = 4.8%). This sparingly soluble substance is almost devoid of mordant dyeing properties. Myricetin.-The tetramethyl ether was demethylated by treat-ment for 2 hours with a boiling mixture of colourless hydriodic acid (d 1.7) (4 parts) and acetic anhydride (1 part). The red crystalline myricetin hydriodide was collected decomposed by hot water, and the yellow precipitate isolated.The substance crystallised from aqueous alcohol in bright yellow needles and showed all the highly characteristic reactions of myricetin as described by Perkin and his collaborators (Eoc. cit.). The remarkable behaviour with alkalis and with mineral acids the reactions with lead acetate and ferric chloride and the dyeing properties were examined. The melting point was about 360° but as stated by Perkin the deter-mination is difficult on account of blackening. For this reason the substance was converted in the usual manner into the hexa-acetate, which crystallised from alcohol in long silky colourless needles, In. p. 214-215" * (corr.) (Found C = 56.8; H = 3.7. Calc. for C2,H2,0,, C = 56.8; H = 3.9%).uncorrected. * The melting point 211-212' given in the literature is presumabl 184 MORGAN AND YABSLEY RESEARCHES ON We are greatly indebted to Professor A. G. Perkin for a specimen of myricetin hexa-acetate. The derivative prepared from natural myricetin when mixed with the synthetical material did not depress its melting point. Direct comparison further confirmed the identity of the specimens. We desire t o thank the Ramsay Memorial Fellowship Trust for a Fellowship (Netherlands) which has enabled one of us to take part in this investigation. THE UNIVERSITY MANCHESTER. [Received November 20th 13241 KALBF AND ROBINSON A SYNTHESIS OF MYRICETIN ETC. 181 XXVIIL-A Synthesis of Myricetin and of a Galangin Monomethyl Ether Occurring in Galanga Root. By JAN IZALFF and ROBERT ROBINSON.ALLAN and ROBINSON (J. 1924 125 2192) have described an extremely simple method of preparation of 7-hydroxy-3-methoxy-flavone by hydrolysis of the product of the action of benzoic anhydride and sodium benzoate on o-methoxyresacetophenone a t 180-185". On applying the reaction to w-methoxyphloraceto-phenone (Slater and Stephen J. 1920 117 316) we have now obtained an excellent yield of 5 7-dihyciroxy-3-methoxyflavone (I), which is identical with the galangin monomethyl ether isolated from galanga root the rhizome of Alpinia officinarum (Hance) by Testoni (Gazzetla 1900 30 ii 327). The formation of phloro-glucinol and benzoic acid by the aerial oxidation of an alkaline solution of the substance was observed by A. G. Perkin and Allison (J.1902 81 472) and led to the suggestion that it is galangin 3-monomethyl ether. This conclusion is now confirmed by syn-thesis and the occurrence of the methyl group in this position in the molecule of a naturally occurring flavonol is of interest because there is reason to believe that certain of the anthocyanidins are similarly constituted in respect of this structural detail. The attractive view that the anthocyanin and anthoxanthin pigments are intimately and genetically related derives support from the accumulation of such coincidences. Galangin itself is obtained by demethylation of the methyl ether and this flavonol has been previously synthesised by v. Kostanecki and Tambor (Ber. 1899, 32 2260). 0 0 Myricetin was first isolated by A. G. Perkin and Hummel (J., 1896 69 1287) from the bark of Myrica nagi (Thunb) and as a result of this and subsequent investigations (Perkin J.1902 81, 204; 1911 99 1721 ; Perkin and Phipps J. 1904 85 62) has been regarded as 3 5 7 3' 4' 5' :-hexahydroxyflavone (I1 with H in place of Me). Myricetin is somewhat widely distributed in nature and it is the flavonol which should yield a delphinidin salt on reduction in acid solution. The synthesis of the colouring matter is a further example of the new and convenient method of prepara-tion of the flavonols. o-Methoxyphloroacetophenone was heate 182 KALFF AND ROBINSON A SYNTIIESIS OF MYRICETIN with trimethylgallic anhydride and sodium trimethylgallate and the product hydrolysed. The 5 7-dihydroxy-3 3' 4' 5'-tetra-methoxyflavone (11) thus obtained yields myricetin on demethyl-ation.Phloroglucinol is converted in this manner into mvyricetin through two isolated intermediate stages only and the synthesis is also available as a preparative method. E x P E R I AT E N T A L. Galangin 3-Monomethyl Ether (I).-A mixture of w-methoxy-phloroacetophenone (5 g . ) sodium benzoate (6 g.) and benzoic anhydride (15 g.) was heated (oil-bath at MOO) during 8 hours, after which alcohol (75 c.c,) was added to the dark red semi-solid mass and potassium hydroxide (8.5 g.) in water (10 c.c.) gradually introduced to the boiling solution. After refluxing for Q hour the greater part of the alcohol was evaporated the residue dissolved in water and the flavonol precipitated as a brown powder by saturating the liquid with carbon dioxide collected washed and dried (6.5 g.).The substance was purified through its diacetyl derivative prepared by the action of boiling acetic anhydride during 2 hours. After two crystallisations from alcohol (charcoal) the substance was obtained in long very pale yellow needles m. p. 175-176" (Found : C = 65.3; H = 4.4. C,,H,,O requires C = 65-2; H = 4.4 yo). Testoni (Gazzeita 1900 30 ii 327) states that the diacetate derived from the galangin monomethyl ether from galanga root melts a t 175-176'. The diacetylgalangin methyl ether was hydrolysed by means of an excess of 10% aqueous potassium hydroxide on the steam-bath. The phenol precipitated by hydrochloric acid may be crystallised from alcohol acetic acid or ethyl acetate in rectan-gular yellow plates m.p. 299" soluble in dilute aqueous potassium hydroxide to an intense yellow solution (sodium salt yellow needles) and in sulphuric acid to a yellow solution exhibiting green fluor-escence (Found C = 67.2; H = 4.4. CI6Hl2O5 requires C = 67.6; 13 = 4.3%). The properties of this substance agree with those ascribed to natural galangin monomethyl ether by Testoni (Zoc. cit.) and the identity was proved by the fact that the melting point of the synthetical material was not lowered by admixture with the natural product for a specimen of which we are greatly indebted to Professor A. G. Perkin. Demethylation by means of boiling hydriodic acid (d 1.'7) mixed with a quarter of its weight of acetic anhydride during 40 minutes resulted in the formation of galangin m.p. 214-215" after crystallisation from alcohol. Myricetin 3 3' 4' 5I-Tetramethyl Ether (II).-Pyridine (52 g.) was gradually added to a solution of trimethylgalloyl chloride (35 g.) (Perkin and Weizmann J. 1906 89 1655) in ether (250 c.c. AND OF A GALANGIN MONOMETHYL ETHER ETC. 183 and after 2 hours ice and then water was gradually introduced, and the trimethyl gallic anhydride which is sparingly soluble in ether collected washed with dilute aqueous sodium carbonate solution and dried (yield 75%). This product melted a t 159" (corr.) and was employed without further purification (Fischer and Freudenberg Ber. 1913 46 1129 give 160-161" [corr.] as the m. p. of the pure substance). A mixture of trimethylgallic anhydride (23 g.)? sodium trimethylgallate (10 g.) and o-methoxyphloro-acetophenone (4.5 g.) was heatcd a t 175" for 3 hours.The mixture was a t first completely fluid but as the reaction proceeded it became a dark red paste. As in the previous example the flavonol was isolated by treatment of the crude product with an alcoholic solution of potassium hydroxide (8 g.) and precipitation of the phenolic material by means of carbon dioxide after removal of the alcohol and solution of the residue in water. The crude material (8.2 g.) was acetylated by boiling with an excess of acetic anhydride and the derivative crystallised from alcohol. 3 3' 4' 5'-Tetramethylmyricetin diacetate was obtained in long pale yellow needles m. p. 159" (corr.) (Found C = 60.3; H = 4.9. C23H2a0, requires C = 60.2; H = 4.9%).On hydro-lysis by means of boiling concentrated hydrochloric acid this derivative yields myricetin tetramethyl ether which crystallises from alcohol in thin glistening pale yellow plates m. p. 276-277-5" (Found C = 60.6 ; H = 4.8. CI9Hl8O8 requires C = 60.9 ; H = 4.8%). This sparingly soluble substance is almost devoid of mordant dyeing properties. Myricetin.-The tetramethyl ether was demethylated by treat-ment for 2 hours with a boiling mixture of colourless hydriodic acid (d 1.7) (4 parts) and acetic anhydride (1 part). The red crystalline myricetin hydriodide was collected decomposed by hot water, and the yellow precipitate isolated. The substance crystallised from aqueous alcohol in bright yellow needles and showed all the highly characteristic reactions of myricetin as described by Perkin and his collaborators (Eoc.cit.). The remarkable behaviour with alkalis and with mineral acids the reactions with lead acetate and ferric chloride and the dyeing properties were examined. The melting point was about 360° but as stated by Perkin the deter-mination is difficult on account of blackening. For this reason the substance was converted in the usual manner into the hexa-acetate, which crystallised from alcohol in long silky colourless needles, In. p. 214-215" * (corr.) (Found C = 56.8; H = 3.7. Calc. for C2,H2,0,, C = 56.8; H = 3.9%). uncorrected. * The melting point 211-212' given in the literature is presumabl 184 MORGAN AND YABSLEY RESEARCHES ON We are greatly indebted to Professor A. G. Perkin for a specimen of myricetin hexa-acetate. The derivative prepared from natural myricetin when mixed with the synthetical material did not depress its melting point. Direct comparison further confirmed the identity of the specimens. We desire t o thank the Ramsay Memorial Fellowship Trust for a Fellowship (Netherlands) which has enabled one of us to take part in this investigation. THE UNIVERSITY MANCHESTER. [Received November 20th 13241

ISSN:0368-1645    

DOI:10.1039/CT9252700181

出版商:RSC    

年代:1925

数据来源: RSC

摘要:

184 MORGAN AND YABSLEY RESEARCHES ON XXIX. -Researches on .Residual Afinity und Co-ordina-tion. Part X X I I I . Interactions of Trimethyl-stibine and Platinic and Palladous Chlorides. By GILBERT T. MORGAN and VICTOR EMMANUEL YARSLEY. THE lower chlorides of platinum and palladium combine additively with ammonia pyridine thioethers selenoethers and the trialkyl-phosphines and -arsines to give rise to co-ordination compounds of the general types PtC12,2X PtCI2,4X PdCI2,2X and PdC12,4X. I n the case of the amine and pyridine derivatives of platinous chloride there is considerable foundation for the belief that the compounds PtC12,2X exist in cis- and trans-modifications the four associating units and the central platinum atom being regarded as being in the same plane.A change of orientation from this coplanar arrangement to a tetrahedral configuration would however result in the disappearance of the above-mentioned cis- and trans-isomerism. This change may occur with an increase in the atomic volume of the associating units and although coplanar arrangement may be the rule with amines it by no means follows that this configuration will persist in the additive compounds with phosphines and arsines. The compounds with trimethyl- and triethyl-phosphines were discovered by Cahours and Gal (Compt. rend. 1870 70 897; 71, 208 1381) who obtained two products of empirical formula PtC12,2PR, in each case one white and the other yellow. Trans-formation of the latter to the former modification was noticed on heating but no evidence was given or has since been forthcoming, that the two substances have the same molecular complexity.These authors also obtained two isomeric arsenical derivatives, PtC12,2As(C2H& both of which were yellow but differed in solubility. Rut here again there is no evidence as to molecular complexity RESIDUAL AFFINITY AND CO-ORDINATION. PART XXIII. 185 In the experiments described below chloroplatinic acid and palladous chloride have been treated in turn with trimethylstibine. With the platinic compound reduction occurs giving rise to tri-methylstibine dichloride and the resulting platinous compound then interacts with more trimethylstibine forming one or two additive compounds according as to whether the reaction occurs in aqueous or alcoholic solution In the former medium an orange product is formed which is insoluble in water and organic solvents.I n alcohol this orange compound is precipitated but a soluble substance is also formed which crystallises from organic media in pale yellow leaflets. Analyses and molecular-weight determinations indicate that the soluble yellow product is bistrilmethylstibinedichloroplatinum (11) . The orange substance is evidently either isomeric or polymeric with this yellow compound for it passes quantitatively into the latter a t 60" or when left for several months at the ordinary temperature. Owing to the insolubility of the orange compound in all neutral solvents its molecular complexity cannot be determined by physical methods but its structure has been ascertained by preparing it in two other ways.H,PtC16 + (CH,),Sb = H2PtC14 + (CN,),SbCl,. PtCl + Sb(CH,),. I -(I.) [Pt,4(CK3),Sb]PtC1,. orange insoluble dimeride. W.)[ Pt ,4 (CH,),S b]PdC14. (IV.) pt ,~(c~H,),s~IP~c~ 6. golden-yellow insoluble. 1. With excess of trimethylstibine the yellow and orange com-pounds are both converted slowly into the soluble tetrakistrirnethyl-stibineplatinous chloride (111) and this salt on treatment with cold aqueous potassium platinochloride gives rise to the orange com-pound which is thereby shown to be tetra~istrimet~ylstibine-platinous platiraochloride ( I ) . With chloroplatinic acid or palladou 186 MORGAN AND YARSLEY RESEARCHES ON ,chloride tetrakistrimethylstibineplatinous chloride gives rise respec-tively to tetrakistrimethylstibineplatinous platinichloride (IV) or tetrakistrirnethylstibineplatin~~s palladochloride (V).2. The former of those two salts when hydrolysed with excess of chloroplatinic acid furnishes bistrimeth ylstibinedichloroplatinum (11) and tetrakistrimethylstibineplatinous platinochloride (I) in the proportions of 17 1. In the palladium series trimethylstibine and palladous chloride interact at low temperatures to form an orange additive product, but this changes spontaneously on slight rise of temperature to a yellow substance bistrimethylstibinedichloro~alladizLm (VI). Excess *of trimethylstibine converts this to the soluble orange tetrakistri-methylstibinepalladous chloride (VII) a soluble salt less stable than (vI.) [2(CH&3b,PdC12]. its platinum analogue which did not give with palladous chloride an insoluble product corresponding with the orange dimeride of the platinous series.Digested with dilute hydrochloric acid the tetrakis compound is converted into a light yellow crystalline substance trimethyl-stibinedichloropall~ium hydrochloride (VIII) [(CH,),Sb,PdC13]H, which unlike the other pallado-derivatives is stable on keeping. E s P E E I ni E N T A L. Trimethylstibine being spontaneously inflammable in air was manipulated in the apparatus shown in the accompanying figure. The base was prepared by the Grignard reaction (Hibbert Ber., 1906 39 160) and converted into trimethylstibine dibromide by running its ethereal solution into bromine diluted with the same solvent. Weighed quantities of the dibromide are introduced into flask A, together with a small quantity of water and the calculated amount of finely granulated zinc (Kahlbaum No.1). The air in the appara-tus having been previously expelled by a stream of carbon dioxide, t'he mixture is distilled and the trimethylstibine collected in the graduated receiver B. The reaction vessel E is turned through an angle of 120" by means of the movable rubber joint J so that the filter disk L is raised above the reacting liquids. A slight excess of aqueous platinic or palladous chloride solution is delivered into E from the tap funnel D and to this is slowly added the cal-culated amount of trimethylstibine from the graduated receiver B. As the tertiary stibine is not miscible with aqueous solutions the chemical combination is facilitated by shaking the vessel E and when the reaction is completed the apparatus is rotated so that th RESIDGAL AFFINITY AND CO-ORDINATION.PART XSIII. 187 attachments of vessel E are now in the vertical position as shown by the diagram. By aspiration a t K the liquid contents of E are drawn through the filter L on which the insoluble product is collected. The precipitate is now washed with ether introduced through the tap funnel C and the ethereal washings are aspirated into the receiver F. Here the aqueous and ethereal filtrates are separated, the former being drawn off into the flask G whilst the latter is collected in distilling flask H which is fitted with a condenser P. On distilling off the solvent a residue is obtained of the ether-soluble product which is shown below to be trimethylstibine dichloride.When alcoholic platinic chloride is employed the re-action is more vigorous because of the miscibility of trimethyl-stibine with this medium. The insoluble product is collected as before on filter L whilst the alcoholic filtrate and wash-ings are drawn into flask H. On removing the solvent the residue contains trimethyl-stibine dichloride and bistri-methylstibinedichloroplatinum (or palladium). The whole apparatus is so designed that these platinous and palladous derivatives of highly inflammable trimethyl-FIQ. 1. stibine can be prepared collected and desiccated in an inert atmosphere and out of contact with air. I. Platinum Series. Tetral%istrimethylstib~neplatinous Plcttinochloride (I) .-The addition of trimethylstibine to aqueous platinic chloride in the air-free apparatus resulted in the formation of an orange precipitate insoluble in water or in organic media which was washed success-ively with water and ether and dried at the ordinary temperature : 0.2200 gave 0.0990 CO, 0.0639 H,O C = 12.24 H = 3-21 ; 0.1807 gave 0.0905 AgC1 C1= 12.39; 0.0819 gave 0.0454 Sb,S, Sb = 39.86; 0-2465 gave 0.0812 Pt Pt = 32.94.C,H,,CI,Sb,Pt requires C = 12.17 H = 3-01 C1 = 11.9 Sb = 40.2 Pt = 32.72% 188 MORGAN AND YARSLEY RESEARCHES ON When left €or several months or rapidly on heating a t 65" this substance undergoes depolymerisation to the pale yellow bistri-methylstibinedichloroplatinum. Both modifications are produced when the interaction of trimethylstibine and platinic chloride is effected in alcoholic solution; the orange dimeric compound is precipitated whereas the monomeric substance remains in solution.Tetralristrimethylstibineplatinous platinochloride was also obtained by the following methods which throw light on its mole-cular complexity. A slight excess of aqueous potassium platinochloride was added to tetrakistrimethylstibineplatinous chloride also dissolved in water, when the orange compound was precipitated quantitatively. This preparation was insoluble in organic solvents and changed a t 60" in% bistrimethylstibinedichloroplatinum. 2. From tetrakistrimethylstibineplatinous platinichloride (p. 189). When treated with a slight excess of aqueous chloroplatinic acid, this platinichloride gave a pale yellow deposit not entirely soluble in organic solvents and leaving in each instance a small amount of orange residue.The ratio of soluble to insoluble product was as 17 1. Moreover when heated at 65" the orange substance changed in the characteristic manner to the yellow soluble form separating from alcohol in pale yellow leaflets 0.1139 gave 0.0553 AgC1, C1 = 12.00; 0.1133 gave 0.0653 Sb,S3 0.0364 Pt Sb = 41.1, Pt = 32.29. C,H,,Cl,Sb,Pt requires C = 12-17 H = 3.01, C1 = 11.9 Sb = 40.2 Pt = 32.72%. Bistrimeth ylstibinedichloro~lati~u~ (11) .-When trimethylstibine and platinic chloride interact in alcoholic solution the preceding orange insoluble compound separates forthwith leaving in solution bistrimethylstibinedichloropla~inum and trimethylstibine dichloride.After distilling off the solvent the latter product is removed by ether leaving the co-ordination compound in a state of purity: 0.1362 gave 0.0661 AgC1 C1 = 12-32. Molecular weight in chloro-form gave M = 605. C,H18C1,Sb,Pt requires c1 = 11.9%; M = 600. This monomeric compound was also prepared by heating its polymeride a t 60" for several hours. The preparation crystallised from alcohol in pale yellow leaflets and did not yield the green salt of Rfagnus when treated with Reiset's chloride [Pt,4N€13]Cl : 0.1009 gave 0.0450 CO, 0.0303 H,O C = 12.12 H = 3.29 ; 0.1054 gave 0.0526 AgCl C1 = 12.38 ; 0.1188 gave 0.0663 Sb2S3 Sb = 40.12; 0.1165 gave 0.0379 Pt Pt = 32-54 M (in chloroform)= 634.7. C,H,,Cl,Sb,Pt requires C = 12.17 H = 3.01 C1 = 11.9, 1.Prom tetrakistrimethylstibine~latinous chloride (111). Sh = 40.2 Pt = 32072%; M = 600 RESIDUAL AFFINITY AND CO-ORDINATION. PART XXIII. 189 The by-product soluble in ether was identified as trimethylstibine dichloride by recrystallisation from this solvent when it separated in colourless six-sided crystals 0.1271 gave 0.1664 AgCl Cl = 30.02. C,H9C1,Sb requires C1 = 30.03%. This dichloride is also formed on passing chlorine into an alcoholic solution of bistrimethyl-s tibinedic hloroplatinum. When treated in alcoholic solution with hydroxylamine hydYo-chloride and sodium acetate bistrimethylstibinedichloroplatinum was completely reduced. With excess of pyridine the bistrimethyl-stibine derivative yields well-defined colourless needles of tetra-pyridineplatinous chloride readily soluble in water or organic solvents.The pyridine was estimated by the method of Harvey and Sparks ( J . Xoc. Chem. Ind. 1918 31 4 1 ~ ) 0.0495 gave Py = 55.0 ; 0.0434 gave 0.0215 AgCl C1 = 12.25. C2&,,N4PtC1, requires Py = 54.3 C1 = 12.16%. Tetrakistrimeth ylstibineplatinous Chloride (III).-An attempt to prepare this compound by adding excess of trimethylstibine to platinous chloride resulted in the formation of the orange poly-meride. This product when treated with more trimethylstibine, dissolved and the solution gave immediately a dark orange-brown precipitate readily soluble in water or organic solvents separating from the latter in orange-brown crystals. These are somewhat plastic and difficult to purify and hence the compound was charac-terised by conversion into its chloroplatinate.For this purpose, the calculated amount of chloroplatinic acid in aqueous solution was mixed with the tetrakis compound when a golden-yellow deposit was obtained 0.0802 gave 0-247 Pt Pt = 30.81. CI,H,6C1GSb,Pt requires Pt = 30.80%. Tetrakistrimetkylstibineplatinous palladochloride (V) prepared by adding aqueous palladous chloride to an alcoholic solution of the tetrakis compound crystallised from alcohol in brown leaflets which were very unstable being decomposed completely on exposure to air for 24 hours 0.0339 gave 0.0210 Sb,S, 0.0056 Pt 0.0032 Pd; Sb = 43.9 Pt = 17.08 Pd = 9.46. C1,H&1,SbPtPd requires Sb = 43.6 Pt = 17.52 Pd = 9.59%. [2(C4H,),Sb.PtC1,]. -Attempts to prepare the higher homologues of trimethylstibine-dichloroplatinum by adding triethylstibine and tri-n-butylstibine to aqueous solutions of platinic chloride led to very unstable ill-defined products from which crystalline bistrialkylstibinedichloro-platinums could not be isolated in a state of purity.Analysis of the higher homologue showed that the product had undergone extensive decomposition. Bistri - n - butylstibinedichloroplatinum 190 RESIDUAL AFFINITY AND CO-ORDINATION. PAXT XXIII. 11. Palladium Series. Bistrimet~ylstibinedichloropalladiu~ (VI).-On adding trimethyl-stibine to an aqueous solution of palladous chloride cooled in a freezing mixture an orange-yellow deposit separated the colour of which persisted at the low temperature. As the temperature rose to normal the product became lemon-yellow and retained this colour on drying.The product was soluble in alcohol or chloro, form but insoluble in water or ether. On prolonged warming, it decomposed without melting liberating metallic palladium : 0.1059 gave 0.0570 CO, 0.0352 H,O C = 14-60 H = 3.69 ; 0.0568 gave 0.0256 PdSb 0.0323 AgCl Pd = 21.09 C1 = 14.01 J M in chloroform= 515. C,H18Cl,Sb,Pd requires C = 14.2 H =I 3-58, Pd = 21.0 C1 = 13.95%; M = 508. Tetrakistrimethylstibinepalladous Chloride (VII).-The more soluble tetrakis compound formed in the preceding preparation separated from the aqueous filtrate in well-defined golden-orange needles contaminated with trimethylstibine dichloride the latter being removed by ether. The tetrakis compound was readily soluble in water but was decomposed by boiling although it was more stable than the bis compound 0.0957 gave 0.0595CO2, 0.0292 H,O C = 17.00 H = 3.42; 0.0616 gave 0-0079 Pd Pd = 12.80.C,,H36C1,Sb,Pd requires C = 17.05 H = 4-28 Pd = 12.6%. This tetrakis compound was also obtained by the action of excess of trimethylstibine on bistrimethylstibinedichloropalladium, although the yield was diminished by reduction of a portion of the palladium present in the latter reagent. The stability of the resulting product was increased materially by keeping it in the dark throughout its preparation and separation. When boiled for some time with dilute hydrochloric acid or a large excess of chloroform, this tetrakis derivative was converted into a lemon-yellow substance (VIII) soluble in water or organic media and distinctly acidic to bromophenol-blue.Unlike the other pallado-derivatives (VI and VII) this product was stable on keeping in the air and gave a light brown precipitate with czsium hydroxide 0.1121 gave 0-0490 Sb,S, and 0.0321 Pd Sb = 31.1 Pd = 28.6. C3H1,C1,SbPd requires Sb = 32-03 Pd = 28.07%. The authors desire to express their thanks to the Advisory Council of the Depalrtment of Scientific and Industrial Research to the Salters' Institute of Industrial Chemistry and to Messrs. Brunner Mond and Company Limited for grants which have helped to defray the expense of this investigation. UNIVERSITY OF BIRMINGHAM, EDGBASTON. [Received November 17th 1924. 184 MORGAN AND YABSLEY RESEARCHES ON XXIX.-Researches on .Residual Afinity und Co-ordina-tion. Part X X I I I . Interactions of Trimethyl-stibine and Platinic and Palladous Chlorides. By GILBERT T. MORGAN and VICTOR EMMANUEL YARSLEY. THE lower chlorides of platinum and palladium combine additively with ammonia pyridine thioethers selenoethers and the trialkyl-phosphines and -arsines to give rise to co-ordination compounds of the general types PtC12,2X PtCI2,4X PdCI2,2X and PdC12,4X. I n the case of the amine and pyridine derivatives of platinous chloride there is considerable foundation for the belief that the compounds PtC12,2X exist in cis- and trans-modifications the four associating units and the central platinum atom being regarded as being in the same plane. A change of orientation from this coplanar arrangement to a tetrahedral configuration would however result in the disappearance of the above-mentioned cis- and trans-isomerism.This change may occur with an increase in the atomic volume of the associating units and although coplanar arrangement may be the rule with amines it by no means follows that this configuration will persist in the additive compounds with phosphines and arsines. The compounds with trimethyl- and triethyl-phosphines were discovered by Cahours and Gal (Compt. rend. 1870 70 897; 71, 208 1381) who obtained two products of empirical formula PtC12,2PR, in each case one white and the other yellow. Trans-formation of the latter to the former modification was noticed on heating but no evidence was given or has since been forthcoming, that the two substances have the same molecular complexity.These authors also obtained two isomeric arsenical derivatives, PtC12,2As(C2H& both of which were yellow but differed in solubility. Rut here again there is no evidence as to molecular complexity RESIDUAL AFFINITY AND CO-ORDINATION. PART XXIII. 185 In the experiments described below chloroplatinic acid and palladous chloride have been treated in turn with trimethylstibine. With the platinic compound reduction occurs giving rise to tri-methylstibine dichloride and the resulting platinous compound then interacts with more trimethylstibine forming one or two additive compounds according as to whether the reaction occurs in aqueous or alcoholic solution In the former medium an orange product is formed which is insoluble in water and organic solvents.I n alcohol this orange compound is precipitated but a soluble substance is also formed which crystallises from organic media in pale yellow leaflets. Analyses and molecular-weight determinations indicate that the soluble yellow product is bistrilmethylstibinedichloroplatinum (11) . The orange substance is evidently either isomeric or polymeric with this yellow compound for it passes quantitatively into the latter a t 60" or when left for several months at the ordinary temperature. Owing to the insolubility of the orange compound in all neutral solvents its molecular complexity cannot be determined by physical methods but its structure has been ascertained by preparing it in two other ways. H,PtC16 + (CH,),Sb = H2PtC14 + (CN,),SbCl,.PtCl + Sb(CH,),. I -(I.) [Pt,4(CK3),Sb]PtC1,. orange insoluble dimeride. W.)[ Pt ,4 (CH,),S b]PdC14. (IV.) pt ,~(c~H,),s~IP~c~ 6. golden-yellow insoluble. 1. With excess of trimethylstibine the yellow and orange com-pounds are both converted slowly into the soluble tetrakistrirnethyl-stibineplatinous chloride (111) and this salt on treatment with cold aqueous potassium platinochloride gives rise to the orange com-pound which is thereby shown to be tetra~istrimet~ylstibine-platinous platiraochloride ( I ) . With chloroplatinic acid or palladou 186 MORGAN AND YARSLEY RESEARCHES ON ,chloride tetrakistrimethylstibineplatinous chloride gives rise respec-tively to tetrakistrimethylstibineplatinous platinichloride (IV) or tetrakistrirnethylstibineplatin~~s palladochloride (V).2. The former of those two salts when hydrolysed with excess of chloroplatinic acid furnishes bistrimeth ylstibinedichloroplatinum (11) and tetrakistrimethylstibineplatinous platinochloride (I) in the proportions of 17 1. In the palladium series trimethylstibine and palladous chloride interact at low temperatures to form an orange additive product, but this changes spontaneously on slight rise of temperature to a yellow substance bistrimethylstibinedichloro~alladizLm (VI). Excess *of trimethylstibine converts this to the soluble orange tetrakistri-methylstibinepalladous chloride (VII) a soluble salt less stable than (vI.) [2(CH&3b,PdC12]. its platinum analogue which did not give with palladous chloride an insoluble product corresponding with the orange dimeride of the platinous series.Digested with dilute hydrochloric acid the tetrakis compound is converted into a light yellow crystalline substance trimethyl-stibinedichloropall~ium hydrochloride (VIII) [(CH,),Sb,PdC13]H, which unlike the other pallado-derivatives is stable on keeping. E s P E E I ni E N T A L. Trimethylstibine being spontaneously inflammable in air was manipulated in the apparatus shown in the accompanying figure. The base was prepared by the Grignard reaction (Hibbert Ber., 1906 39 160) and converted into trimethylstibine dibromide by running its ethereal solution into bromine diluted with the same solvent. Weighed quantities of the dibromide are introduced into flask A, together with a small quantity of water and the calculated amount of finely granulated zinc (Kahlbaum No.1). The air in the appara-tus having been previously expelled by a stream of carbon dioxide, t'he mixture is distilled and the trimethylstibine collected in the graduated receiver B. The reaction vessel E is turned through an angle of 120" by means of the movable rubber joint J so that the filter disk L is raised above the reacting liquids. A slight excess of aqueous platinic or palladous chloride solution is delivered into E from the tap funnel D and to this is slowly added the cal-culated amount of trimethylstibine from the graduated receiver B. As the tertiary stibine is not miscible with aqueous solutions the chemical combination is facilitated by shaking the vessel E and when the reaction is completed the apparatus is rotated so that th RESIDGAL AFFINITY AND CO-ORDINATION.PART XSIII. 187 attachments of vessel E are now in the vertical position as shown by the diagram. By aspiration a t K the liquid contents of E are drawn through the filter L on which the insoluble product is collected. The precipitate is now washed with ether introduced through the tap funnel C and the ethereal washings are aspirated into the receiver F. Here the aqueous and ethereal filtrates are separated, the former being drawn off into the flask G whilst the latter is collected in distilling flask H which is fitted with a condenser P. On distilling off the solvent a residue is obtained of the ether-soluble product which is shown below to be trimethylstibine dichloride.When alcoholic platinic chloride is employed the re-action is more vigorous because of the miscibility of trimethyl-stibine with this medium. The insoluble product is collected as before on filter L whilst the alcoholic filtrate and wash-ings are drawn into flask H. On removing the solvent the residue contains trimethyl-stibine dichloride and bistri-methylstibinedichloroplatinum (or palladium). The whole apparatus is so designed that these platinous and palladous derivatives of highly inflammable trimethyl-FIQ. 1. stibine can be prepared collected and desiccated in an inert atmosphere and out of contact with air. I. Platinum Series. Tetral%istrimethylstib~neplatinous Plcttinochloride (I) .-The addition of trimethylstibine to aqueous platinic chloride in the air-free apparatus resulted in the formation of an orange precipitate insoluble in water or in organic media which was washed success-ively with water and ether and dried at the ordinary temperature : 0.2200 gave 0.0990 CO, 0.0639 H,O C = 12.24 H = 3-21 ; 0.1807 gave 0.0905 AgC1 C1= 12.39; 0.0819 gave 0.0454 Sb,S, Sb = 39.86; 0-2465 gave 0.0812 Pt Pt = 32.94.C,H,,CI,Sb,Pt requires C = 12.17 H = 3-01 C1 = 11.9 Sb = 40.2 Pt = 32.72% 188 MORGAN AND YARSLEY RESEARCHES ON When left €or several months or rapidly on heating a t 65" this substance undergoes depolymerisation to the pale yellow bistri-methylstibinedichloroplatinum. Both modifications are produced when the interaction of trimethylstibine and platinic chloride is effected in alcoholic solution; the orange dimeric compound is precipitated whereas the monomeric substance remains in solution.Tetralristrimethylstibineplatinous platinochloride was also obtained by the following methods which throw light on its mole-cular complexity. A slight excess of aqueous potassium platinochloride was added to tetrakistrimethylstibineplatinous chloride also dissolved in water, when the orange compound was precipitated quantitatively. This preparation was insoluble in organic solvents and changed a t 60" in% bistrimethylstibinedichloroplatinum. 2. From tetrakistrimethylstibineplatinous platinichloride (p. 189). When treated with a slight excess of aqueous chloroplatinic acid, this platinichloride gave a pale yellow deposit not entirely soluble in organic solvents and leaving in each instance a small amount of orange residue.The ratio of soluble to insoluble product was as 17 1. Moreover when heated at 65" the orange substance changed in the characteristic manner to the yellow soluble form separating from alcohol in pale yellow leaflets 0.1139 gave 0.0553 AgC1, C1 = 12.00; 0.1133 gave 0.0653 Sb,S3 0.0364 Pt Sb = 41.1, Pt = 32.29. C,H,,Cl,Sb,Pt requires C = 12-17 H = 3.01, C1 = 11.9 Sb = 40.2 Pt = 32.72%. Bistrimeth ylstibinedichloro~lati~u~ (11) .-When trimethylstibine and platinic chloride interact in alcoholic solution the preceding orange insoluble compound separates forthwith leaving in solution bistrimethylstibinedichloropla~inum and trimethylstibine dichloride.After distilling off the solvent the latter product is removed by ether leaving the co-ordination compound in a state of purity: 0.1362 gave 0.0661 AgC1 C1 = 12-32. Molecular weight in chloro-form gave M = 605. C,H18C1,Sb,Pt requires c1 = 11.9%; M = 600. This monomeric compound was also prepared by heating its polymeride a t 60" for several hours. The preparation crystallised from alcohol in pale yellow leaflets and did not yield the green salt of Rfagnus when treated with Reiset's chloride [Pt,4N€13]Cl : 0.1009 gave 0.0450 CO, 0.0303 H,O C = 12.12 H = 3.29 ; 0.1054 gave 0.0526 AgCl C1 = 12.38 ; 0.1188 gave 0.0663 Sb2S3 Sb = 40.12; 0.1165 gave 0.0379 Pt Pt = 32-54 M (in chloroform)= 634.7. C,H,,Cl,Sb,Pt requires C = 12.17 H = 3.01 C1 = 11.9, 1.Prom tetrakistrimethylstibine~latinous chloride (111). Sh = 40.2 Pt = 32072%; M = 600 RESIDUAL AFFINITY AND CO-ORDINATION. PART XXIII. 189 The by-product soluble in ether was identified as trimethylstibine dichloride by recrystallisation from this solvent when it separated in colourless six-sided crystals 0.1271 gave 0.1664 AgCl Cl = 30.02. C,H9C1,Sb requires C1 = 30.03%. This dichloride is also formed on passing chlorine into an alcoholic solution of bistrimethyl-s tibinedic hloroplatinum. When treated in alcoholic solution with hydroxylamine hydYo-chloride and sodium acetate bistrimethylstibinedichloroplatinum was completely reduced. With excess of pyridine the bistrimethyl-stibine derivative yields well-defined colourless needles of tetra-pyridineplatinous chloride readily soluble in water or organic solvents.The pyridine was estimated by the method of Harvey and Sparks ( J . Xoc. Chem. Ind. 1918 31 4 1 ~ ) 0.0495 gave Py = 55.0 ; 0.0434 gave 0.0215 AgCl C1 = 12.25. C2&,,N4PtC1, requires Py = 54.3 C1 = 12.16%. Tetrakistrimeth ylstibineplatinous Chloride (III).-An attempt to prepare this compound by adding excess of trimethylstibine to platinous chloride resulted in the formation of the orange poly-meride. This product when treated with more trimethylstibine, dissolved and the solution gave immediately a dark orange-brown precipitate readily soluble in water or organic solvents separating from the latter in orange-brown crystals. These are somewhat plastic and difficult to purify and hence the compound was charac-terised by conversion into its chloroplatinate.For this purpose, the calculated amount of chloroplatinic acid in aqueous solution was mixed with the tetrakis compound when a golden-yellow deposit was obtained 0.0802 gave 0-247 Pt Pt = 30.81. CI,H,6C1GSb,Pt requires Pt = 30.80%. Tetrakistrimetkylstibineplatinous palladochloride (V) prepared by adding aqueous palladous chloride to an alcoholic solution of the tetrakis compound crystallised from alcohol in brown leaflets which were very unstable being decomposed completely on exposure to air for 24 hours 0.0339 gave 0.0210 Sb,S, 0.0056 Pt 0.0032 Pd; Sb = 43.9 Pt = 17.08 Pd = 9.46. C1,H&1,SbPtPd requires Sb = 43.6 Pt = 17.52 Pd = 9.59%. [2(C4H,),Sb.PtC1,]. -Attempts to prepare the higher homologues of trimethylstibine-dichloroplatinum by adding triethylstibine and tri-n-butylstibine to aqueous solutions of platinic chloride led to very unstable ill-defined products from which crystalline bistrialkylstibinedichloro-platinums could not be isolated in a state of purity.Analysis of the higher homologue showed that the product had undergone extensive decomposition. Bistri - n - butylstibinedichloroplatinum 190 RESIDUAL AFFINITY AND CO-ORDINATION. PAXT XXIII. 11. Palladium Series. Bistrimet~ylstibinedichloropalladiu~ (VI).-On adding trimethyl-stibine to an aqueous solution of palladous chloride cooled in a freezing mixture an orange-yellow deposit separated the colour of which persisted at the low temperature. As the temperature rose to normal the product became lemon-yellow and retained this colour on drying.The product was soluble in alcohol or chloro, form but insoluble in water or ether. On prolonged warming, it decomposed without melting liberating metallic palladium : 0.1059 gave 0.0570 CO, 0.0352 H,O C = 14-60 H = 3.69 ; 0.0568 gave 0.0256 PdSb 0.0323 AgCl Pd = 21.09 C1 = 14.01 J M in chloroform= 515. C,H18Cl,Sb,Pd requires C = 14.2 H =I 3-58, Pd = 21.0 C1 = 13.95%; M = 508. Tetrakistrimethylstibinepalladous Chloride (VII).-The more soluble tetrakis compound formed in the preceding preparation separated from the aqueous filtrate in well-defined golden-orange needles contaminated with trimethylstibine dichloride the latter being removed by ether. The tetrakis compound was readily soluble in water but was decomposed by boiling although it was more stable than the bis compound 0.0957 gave 0.0595CO2, 0.0292 H,O C = 17.00 H = 3.42; 0.0616 gave 0-0079 Pd Pd = 12.80.C,,H36C1,Sb,Pd requires C = 17.05 H = 4-28 Pd = 12.6%. This tetrakis compound was also obtained by the action of excess of trimethylstibine on bistrimethylstibinedichloropalladium, although the yield was diminished by reduction of a portion of the palladium present in the latter reagent. The stability of the resulting product was increased materially by keeping it in the dark throughout its preparation and separation. When boiled for some time with dilute hydrochloric acid or a large excess of chloroform, this tetrakis derivative was converted into a lemon-yellow substance (VIII) soluble in water or organic media and distinctly acidic to bromophenol-blue. Unlike the other pallado-derivatives (VI and VII) this product was stable on keeping in the air and gave a light brown precipitate with czsium hydroxide 0.1121 gave 0-0490 Sb,S, and 0.0321 Pd Sb = 31.1 Pd = 28.6. C3H1,C1,SbPd requires Sb = 32-03 Pd = 28.07%. The authors desire to express their thanks to the Advisory Council of the Depalrtment of Scientific and Industrial Research to the Salters' Institute of Industrial Chemistry and to Messrs. Brunner Mond and Company Limited for grants which have helped to defray the expense of this investigation. UNIVERSITY OF BIRMINGHAM, EDGBASTON. [Received November 17th 1924.

ISSN:0368-1645    

DOI:10.1039/CT9252700184

出版商:RSC    

年代:1925

数据来源: RSC