摘要:

THE PREPARATION OF MIXED KETONES. 1185 CXVIII. - The Prepmation of Mixed Ketones by Heating the Nixed Calcium Xutts of Oryanic Acids. By ERNEST BOWMAN LUDLAM, M.Sc. (Vict.). THE method of heating a calcium salt in a sulphur vapour bath SO as to form the corresponding ketone and of removing the ketone, as soon as formed, by a current of carbon dioxide (Young, Trans., 1891, 59, 623) gave such remarkably good results in the case of dibenzyl ketone that it seemed desirable to test its general applicability, and, in parti- cular, to extend the method to the case of mixtures of calcium salts. As the yield of crude ketone was 93 per cent. in the simple case where the calcium salt of only one acid was heated, and the whole preparation was effected with ease, it appeared probable that interesting information would be obtained as to the course of the decomposition if the simple salt were replaced by mixtures.Had the yield of unmixed ketone not been so good, it would have made it very difficult to draw any conclusions of value when dealing with mixtures, for, in addition to the slight loss in the formation of the ketones, there is the increased difficulty of separating them from one another and obtaining them pure. On subjecting a mixture of two calcium salts to the action of heat, three ketones are formed and collect together in the distillate. It is possible by collecting the distillate in fractions to effect a preliminary separation, which, however, is only slight, as the ketones are formed simultaneously, distilling and condensing together. This fact made it important to select such ketones as could easily be separated by a subsequent fractional distillation, and this was also convenient for another reason, namely, that in connection with another investigation a ketone was required in which the two groups attached to the carbon atom of the carbonyl group should be markedly different.On heating mixtures of the calcium salts of these two acids, dimethyl, methyl The acids first employed were acetic and phenylacetic.1186 LUDLAM: THE PREPARATION OF MIXED KETONES BY Weight in grams. Ketone. (~cx&JZCO .................... 2 H3>c0 .................... 18 ' 7 7 (C,H,)&O ..................... 9 benzgl, and dibenzyl ketones are obtained, and as they boil respectively at 56*, 21'7O, and 330°, there is no difficulty in separating them by fractional distillation.Moreover, the mixed ketone contains the two radicles methyl and benzyl, which were sufficiently unlike to render the ketone a suitable one for further investigation, Subsequently calcium phenylacetate was distilled with calcium propionate and with calcium butyrate respectively. The fractionation of the ketones obtained from these salts was a.gain quite an easy operation, Per cent. Per cent. number of mol. wt. mols. 6'6 0.115 16'1 60 '0 0.448 62.5 33'4 0'152 21-2 Preparation of Nethyl Benxyl Ketone. The preparation was carried out with various proportions of the two salts, starting with a slight excess of calcium phenylacetate, then using molecular proportions of the two, and, later, increasing the proportion of acetate.(1) I n the first distillation, 20 grams of calcium acetate, previbusly well dried by heating in an air-bath to 140", were thoroughly mixed and ground in a mortar with 45 grams of dry calcium phenylacetate, the latter weight being 6 grams in excess of the calculated quantity required to form a molecular mixture, The mixed salts were placed in a parting flask and heated to the temperature of boiling sulphur ; a current of washed and dried carbon dioxide was passed through and maintained until the decomposition was complete. During the heating, there was just a little frothing, but although the mass became viscid and semi-transparent it did not become quite liquid. The ketone collected in the capillary tube in columns which were carried over into the receiver by the current of carbon dioxide.Towards the close of the distillation, the product became darker in colour and white fumes were formed which con- densed with difficulty, forming a dark coloured oil. Table I gives in the h s t column the weights of the three ketones TABLE I . Mols. Calcium Acetate : Calcium Phenylacehte : : 1 : 1.125.HEATING THE MIXED CALCIUM SALTS OF ORGANIC ACIDS. 1187 ~ Weight in Per cent. grams. Ketone. ______ (CH,),CO ..................... 2 7'4 ..................... $2>CO 7 7 17 59 -3 (CoH,)&O ..................... 7 33.3 as estimated from the results of the fractional distillation. The second column gives the percentage weight of each ketone in the mixture, the third column this weight divided by the molecular weight of the ketone, and the last column the percentage number of molecules of each ketone.(2) A second distillation was carried out in which molecular pro- portions of the calcium salts were employed, namely, 20 grams of calcium acetate to 40 grams of phenylacetate. The heating was effected precisely as in the preceding case, but the arrangements for con- densing were improved, as it was thought there might have been a slight loss of acetone, due to its having been carried away by the carbon dioxide. The crude distillate, after drying over ignited potassium carbonate, weighed 27 grams and on fractionation gave the figures set forth in Table 11. TABLE 11. Nola. Calcium Acetate : Calcium Phertylacetate ; : 1 : 1. I Per cent. number of mol. wt. mole.0.1276 17 *7 61 -4 0-4430 0'1514 21 -3 These figures show that the greater part of the product is the benzyl methyl ketone. The calculated yield of this ketone, if none others were formed, would be 34 grams. Actually, 17 grams were obtained, so that when molecular proportions of the two calcium salts are taken, the yield of the mixed ketone is only 50 per cent. of the amount theoretically possible on the assumption that it was the only ketone formed. I n determining the proportion OF the ketones present, rather more certainty would have been obtained if the method of mid-points had been employed (Young, Trans., 1902, 81, 752). This was not known at the time, but, making allowance for some slight inaccuracy due to imperfect fractionation, the last column shows that the number of molecules of mixed ketone is three times the number of molecules of either of the other two.The low figures for acetone would not permit the above statement to be made with much confidence were it not for the fact that some acetone must have been carried away by the rapid current of carbon dioxide. The weight of the dibenzyl ketone should be three times1188 LUDLAM: THE PREPARATION OF MIXED KETONES BY Per cent. that of the dimethyl ketone, whereas the figures obtained gave a ratio more nearly three and a half to one ; but, as the number of molecules of dimethyl ketone produced should be equal to the number of dibenzyl ketone molecules, for the original mixture contained the two calcium salts in molecular proportion, it seems not only justifi- able, but necessary, to assume that the acetone has been lost by evaporation.(3) The next distillation was of a mixture containing 25 grams of calcium acetate and 35 grams of calcium phenylacetate. The ratio of molecules in such a mixture is 1-4 of the former to 1- of the latter. The results of the distillation are embodied in Table 111. Unfortunately, TABLE 111. iK&. Calcium Acetate : Calcium Phenylacetate : : 1-4 ; 1. - Per cent. mol. wt. Ketone. 17'4 56.5 Weight in grams. 0.2999 0.4217 ..................... (CH,),CO CH H3>c0 ..................... 7 7 4 13 Per cent. 25 -8 50.0 24-2 Per cent. number of mols. 35.5 50.0 14 -5 Per cent. -. mol. wt. 0'445 0 '372 0'11 the total yield was only about 80 per cent. of that obtained in some of the other experiments, and the figures are of much less importance than those derived from experiments in which the total yield of crude unseparated ketones was greater.(4) Two mols. of calcium acetate with one mol. of calcium phenyl- acetate. This molecular ratio is obtained almost exactly, if equal weights of the two salts are employed. In the actual experiments, 30 grams of each of the two salts were taken, ground together, and heated as before. The results obtained from one of these distillations are contained in Table IT, showing that the yield of acetone molecules TABLE IV. Nols. Ca2cium Acetate : Calcium Phernylacetate ; : 2 : 1. (CH,),CO ..................... CH c,a;>CO ..................... (C,H7)2CO ..................... Ketone. 8 15 '5 7'5 Weight in grams. -1 Per cent.number of mols. 48-0 40-2 11.8HEATING THE MIXED CALCIUM SALTS OF ORGANIC ACIDS. 1189 in the distillate is approximately 50 per cent., and of the remainder four-fifths are of the mixed ketone and one-fifth dibenzyl ketone, Preparation of Ethyl Belnxyl Ketone. As this ketone was not wanted in any considerable quantity for investigation, but only to serve as a check on results obtained with methyl and propyl benzyl ketones, between which it stands in the series, the calcium salts themselves are not so carefully purified, fewer distillations were carried out, and the final purification of the ketone was not so elaborate. The results are, in consequence, not strictly comparable with those obtained in the other two cases. In point of time the experiments were not performed until several months after the preparation of the other two ketones had been completed and their investigation commencbd It was then found desirable to prepare this ketone, and see if it yielded derivatives possessing properties intermediate between those exhibited by the corresponding derivatives of the other two ketones, and this was found to be the case.Twenty grams of calcium propionate, and 30 grams of calcium phenylacetate were mixed together and heated. Then the operation mas repeated, and the crude distillate purified by fractionation. I n this case, the diethyl ketone boils at 103', ethyl benzyl ketone at 227O, and dibenzyl ketone, as before, a t 330'. From 48 grams of crude distillate the three ketones were obtained as shown in Table V, and a further purification gave 12.5 gramsof pure ethyl benzyl ketone.TABLE V. Mols. Calcium Propionate : Calcium Phen~lacetate : : 1 : 1. Ketone. (C2Hs)2C0 .................... z;;>co ..................... ......... I (C;',H,),CO ........... Weight in grams. 5 20 15 Per cent. 12-5 50 37-5 Per cent. mol. wt. 0.1456 0.2683 0-1790 Preparation of Propyl Benxyl Ketone. Per cent. number of mols. 24.6 45.3 30.1 (1) Molecular mixtures of calcium butyrate (25 grams) and calcium phenylacetate (37 grams) mere distilled in precisely the same manner described under the preparation of methyl benzyl ketone, Three1190 LUDLAM: THE PREPARATION OF MIXED KETONES BY distillations yielded the figures contained in the first three columns of Table TI, the fourth column being the means from which the figures TABLE VI.Mols. Calcium Bzltyrate : Calcium Phenylacetate ; ; 1 : 1. I. 6 16 5 Ketone. 11. 111. Mean. ---- 5 5 5-3 17 19 17.3 6 7 6 (CsH7)zCO ......... ......... 18.5 60'4 20.1 Weight in grams. 0'1626 25'6 22.4 0.3734 58.7 60'1 0.0998 15.7 17.5 Ketone. (C,H,),CO ............ 23>CO ......... (C7H7),C0 ......... -1- 1-1- Weight in grams. Per cent. Per cent- Per cent. number of mols. 1 I. 11. Mean. -- I --- 6 6 6 195 0.1697 26.5 19 20 19.5 62.7 0.3883 60'4 5 6 5.5 17.8 0-0845 13.1 in the succeeding columns are derived. I n the last column, the percentage number of molecules is calculated from the last and best of the three distillations. It shows satisfactory agreement with the corresponding figures for methyl bmzyl ketone. (2) Two distillations were then made of a mixture containing 37 grams of calcium phenylacetate and 30 grams of calcium butyrate.This is in the proportion of one molecule OF the former to 1.2 molecules of the latter, and the results are tabulated as before. TABLE VII. Mols. Calcium Butyrate : CaZcium Phenylacetate : : 1.2 : 1. - I I I I n this case, as was to be expected, the percentage number of molecules of the lowest ketone has increased, that of the highest has decreased, but the middle ketone has not suffered diminution. As this ketone had not been described, its exact boiling point was not known. A careful fractionation was accordingly performed, a 6' rod and disc " still-head being first employed, but later this was re- placed by a '' pear " dephlegmator possessing twelve bulbs.Finally, aftor seven distillations, a major fraction was obtained boiling betweeqHEATlNG THE MIXED CALCIUM SALTS OF ORGANIC ACIDS. 1191 Dimethyl. phenylacetate. 243' and 244', and the boiling point of the ketone consequently lies between these limits. The barometric pressure was 755 mm., and a very small Geissler thermometer was used, the whole of the column of mercury being immersed in the vapour of the boiling liquid. Since the above determination was made, the ketone has been obtained by an entirely different method (Blnise, Compt. rend., 1901, 133, 1217), and the boiling point given is 238-241'. This specimen is described as possessing the odour of aniseed, which is absent when prepared as described above, although the ketone has a characteristic odour.Its density was d O'/O' = 1.0090. Two determinations of its mole- cular weight in boiling benzene solution gave 164 and 161, whereas C,H7*CO*C7H, has the mol. wt. 162. The apparatus employed was a modification of Landsberger's, which forms the subject of the following note (p. 1193). .__- Methyl benzyl. Dihenzyl. Mode of Decomposition of the Calcium Salts. With regard to the mechanism Qf the changes which take place when the calcium salts of organic acids are heated, the figures obtained in the preparation of methyl benzyl ketone throw some light on the problem. It is unlikely that absolute uniformity in the results could be obtained, however carefully a series of determinations was performed, and how- ever thoroughly the two salts were ground and mixed.As already stated, the mass never becomes liquid, but the decomposition takes place when a pasty stage has been reached. At this stage, the form- ation of any one of the three possible ketones is determined by prox- imity. The results obtained indicate something of the nature of a selective affinity, bending towards the production of the mixed ketone in preference to the simple ketone. Apart from this, the problem is apparently one of chances, Tabulat- ing the ratio of the molecules of the salts originally taken and the molecular yields of ketones obtained, we obtain Table VII, which shows 1 : 1.125 1 : l 1.4 : 1 2:l TABLE VTII. 16-1 17.7 35 -5 48-0 62.5 61.4 50.0 40-2 21 -5 21.3 14'5 11-81192 THE PREPARATION OF MIXED KETONES. the effect that varying the proportion of the calcium salts has on the yield of the ketones.An attempt to plot a probability curve failed owing to the small number and insuf€icient accuracy of the experimental values. Writing the graphic formulze of the calcium salts thus : 8 8 CH,-C-0-Ca-0-C-CH, C,H,-CH,-~-O-Ca-O-~-CHH,~C,H, ’ 0 0 it may be considered that this represents something of the actual internal arrangement of the molecule, and, if the chain remains straight, or eveli approximately so, it is probable that the decomposi- tion is in reality produced by the interaction of two molecules which have ranged up alongside each other, thus : 0 9 giving 2CH,*CO*CH,*C,H, + 2CaC0,. If this explanation is correct, the production of mixed ketone depends on the collisions between the molecules of the different salts, and these depend, firstly, on the mixing, inasmuch as the fusion is not complete, and, secoudly, on the relative proportions of the two salts present.It is clear that where molecular proportions have been taken the chances that the molecule of one salt will collide with a molecule of its own kind, or with a molecule of the other salt, are even. This being so, it would naturally be expected that half of the product would be mixed ketone, and the other half would consist of the fiimple ketones in molecular proportion, that is, the maximum yield of mixed ketone should be50 per cent., and of the other two 25 per cent. each. Reference to Table VIII will, however, show that this is not the case, nor is there any close approximation to it. Consequently it seems probable that there is some directing force favouring the formation of the mixed ketone. From a practical point of view, the figures in Table IX show that the best yield of mixed ketoneobtainable from a given weight of the more expensive salt, in this case calcium phenylacetate, is obtained by using a large excess of the cheaper salt,LUDLAM: A SIMPLE FORM OF LANDSBERCER’S APPARATUS. 1193 1 2 3 4 5 TABLE IX. 20 20 25 30 30 Weight of calcium pheny lacetate. 45 40 35 30 30 Weight of mixed ketone obtained. i a 17 13 15 15.5 Weight of mixed ketone per 100 grams of calcium phenylacetate. 40 42-5 37 50 52 The increase in the yield shown in experiment 5 as compared with that in experiment 1 is sufficiently marked. The intermediate stages are fairly well represented by the figures as displayed, with the excep- tion of experiment 3, owing to the fact that in this experiment the yield of all three ketones was poor. There is little doubt that the average of ,a number of experiments would have yielded a value nearer 45 than 37 when the errors due to a single experiment were elimin- ated. My thanks are due to Dr. F. E, Francis and Professor Young for the use of materials and apparatus which were placed a t my disposal, and for suggestions during the course of the work, UNIVEEGITY COLLEGE, BRIBTOL.

ISSN:0368-1645    

DOI:10.1039/CT9028101185

出版商:RSC    

年代:1902

数据来源: RSC

摘要:

LUDLAM: A SIMPLE FORM OF LANDSBERCER’S APPARATUS. 1193 cx IX.-A Simple Form of Landsberger’s Apparatus foy Determining the Boiling Points of Solutions. By ERNEST BOWMAN LUDLAY, M.Sc. SINCE the appearance of Landsberger’s original paper (Bey., 1898, 31, 458), several modifications of his apparatus for determining molecular weights by the boiling point method have been described. Walker and Lumsden (Trans., 1898, 77, 503) increased the rapidity with which a number of consecutive determinations could be accom- plished by graduating the tube in which the rise of temperature was measured, and, instead of weighing the solvent, measuring its volume, The volumes were reduced to weights by multiplying by the density of the boiling solvent, or, what comes to the same thing, in calculating VOL.LXXXI. 4 K1194 LUDLAM: A SIMPLE FORM OF LANDSBERGER’S APPARATUS the molecular weight from the observations a constant was used, obtained by dividing the usual constant by the density of the boiling solvent. A simplification in the arrangement was effected by Smits (Proc. K. A h d . Wetemch. Amsterdam, 1900, 3, 86), who placed the boiling tube inside the flask in which the solvent was boiled, but did not graduate his tube. What may be considered a distinct improvement was added by C. N. Riiber (Ber., 1901, 34, 1060), namely, a reflux arrangement something like that employed in a fat extractor for returning the condensed vapour again to the flask in which it was generated. This apparatus gives good results, but is somewhat elaborate in design, and seems too fragile to come into general use in the laboratory.About fifteen months ago I re- quired an apparatus which would be easy to work with, and with which good remlts could be ob- tained when only small quantities of the substance, of which the mole- cular weight was being investigated, were available. After devising several forms, the one described below was finally adopted. It com- bines the good points of Walker’s and of Smits’, and in addition possesses features of its own. Unfortunately, it has not been found possible to introduce any reflux arrangement, and at the same time to preserve simplicity. Riiber sacrifices simplicity, and his ad- vantage for specially accurate work is a very real one, inasmuch as the same solvent is used continuously, and consequently any error due to the solvent not being perfectly pure is greatly diminished, and also less of the solvent is required than in the apparatus here described. The solvent is contained in an outer flask, A , of 300 C.C.capacity, and possessing a wide neck provided with a small side tube, 8, through which the solvent is introduced. The flask is fitted with a large cork, through which passes the tube B, about 10 cm. in length and 2.6 cm. in diameter.FOR DETERMINING THE BOILING POINTS OF SOLUTIONS. 1195 In the side of this tube is a small hole, b, t o allow of the passage of the vapour from the boiling liquid into B, and then into C. B is fitted with a cork carrying the innermost tube, C, graduated, and tapering off sharply at the bottom to a small hole.This aperture is made to serve as a valve by means of a little spherical glass bead (u) fused to a platinum wire. The bead is inside the tube, and the wire, passing through the hole, is bent at right angles at a short distance below. I n this way, the bead is allowed just a little up and down motion, but cannot be carried away from the opening by a rush of vapour or liquid, and it allows the stream of vapour to pass easily up into the tube from below, whilst preventing the liquid in the tube from rapidly flowing out into B when the boiling in B is checked. This is all that is required, for the bead need not fit the aperture exactly. The liquid can flow from C into B-which is convenient-but only very slowly. The clip on the tube connected to 8 can be removed to allow access of air when the boiling is stopped and the apparatus allowed to cool.The top part of the tube C is wider than the lower graduated portion, and between the two is an annular trough formed by blowing a bulb, and then, while the glass is still soft, gently pressing the lower tube up into i t and so producing a fold in the glass. Any vapour condensing in the upper part of the tube flows into this trough and is carried away by a side piece to the condenser. By this device, very little condensed vapour is returned to the graduated tube, and the volume of liquid in the tube does not increase so rapidly as it otherwise would do. This trough was the suggestion of Dr. Young, and is a valuable addition to the efficiency of the apparatus. The thermometer is held by a cork which closes the wide neck of this tube, and in the larger forms a side tube was also provided, as shown in the figure, for the introduction of the substance under investigation in the form of pellets, or, in case it was a liquid, by means of a pipette in the usual manner.The side piece was no convenience in the smaller forms of the apparatus owing to the fact that the stem of the thermometer occupied so much space in the narrow tube that there was a danger of the pellet falling into the trough instead of into the graduated tube. It was found in practice to be more convenient and satisfactory rapidly to remove the thermometer, drop in the pellet, and then replace the cork immediately. To carry out a determination, the flask A is half filled with the solvent selected, the tubes B and C and the thermometer are fitted into their places, and the condenser attached to the side tube from C .1196 LUDLAM: A SIMPLE FORM OF LANDSBERGER’S APPARATUS Then the liquid in A is heated by a small, carefully regulated flame and maintained in a state of gentle ebullition.The vapour passes upwards into the neck of the flask, round the tube B, and through the little hole, b, into the space separating B and C. Then it descends to the valve,througE, which it passes upwards into C, and so away to the condenser. I n this way, the innermost tube, in which the increment of temperature is measured, is protected by a double layer of vapour and hot glass from external influences. At the commencement, when all the tubes are cold and the thermo- meter also, a considerable portion of the vapour condenses and accumu- lates in the inner tube C .Through this liquid the vapour passes, the valve causingit to break up into a stream of bubbles which serve the double purpose of heating and thoroughly stirring the liquid. After the vapour has been passing through the apparatus for a few minutes, the tubes get hot, and subsequent condensation in them is slight. Hence the liquid accumulates, only very slowly in the tube C, the actual rate depending on the substance, its boiling point, and heat of vaporisation. I n the case of benzene, t,he tube was usually filled in about half-an-hour or a little longer, whereas with carbon disulphide the increase in volume due to condensation was so slight that it was frequently necessary to add the liquid solvent in order t o obtain suit- able readings, and even then the tube was not full after the vapour had been passing for an hour and a half.It was found that $he tube filled more rapidly when the boiling was vigorous than when it was gentle, provided that, in the latter case, the stream of vapour was not intermittent. The temperature rises very rapidly to within a few tenths of the true boiling point and then gradually attains the constant position. This may take a quarter of an hour from the commencement, the actual time depending on the rapidity of the boiling, and to some extent on the previous history of the thermometer, for if the instru- ment has been recently used for determining the boiling point of the same solvent several times in succession, and has not been used for any other purpose, it very rapidly gives a constant reading.The temperature of the pure solvent having been ascertained in this way, a known weight of the substance under examination is dropped into the boiling solvent, and as it dissolves the temperature rises, attaining a maximum in a few minutes, and then falling very slowly as the volume of the solution increases. When the maximum temperature is observed, a reading of the volume is made. The thermometer is raised above the surface of the liquid by sliding it upwards through the cork, and is not removed from the tube at all. If the boiling flask is touched with the cold hand, sufficientFOR DETERMINING THE BOILING POINTS OF SOLUTIONS. 1197 cooling takes place to stop the stream of bubbles through the graduated tube, and an accurate reading of the volume can be taken.The valve prevents the solution running back into B, the correct volume is easily read off, and the boiling once more allowed to proceed. The whole operation of reading the volume need not take more than twenty seconds. By taking several readings, there is no difficulty in obtaining three or four determinations from one quantity of substance, and practically without disturbing the thermometer. Further, a second pellet of the substance may be added, and, after taking several readings, a third may be introduced. Thus, in one case, using carbon disulphide as solvent, three pellets were introduced and seven readings were obtained without interrupting the boiling for more than a few seconds.I n order to ensure a uniform rate of ebullition, the gas supply was regulated by the device due to Sakurai (Trans., 1892, 61, 995) whereby alteration in gas pressure is minimised. The bench gas tap is opened to the full and is connected to two bunsen burners, one much larger than the other. The large one is kept burning full on, and the small one has its supply of gas further regulated by a screw clip. As the smaller flame is using only a small fraction of the quantity of gas used by the large burner, the latter acts as a most efficient regulator for changes in the gas pressure, which may be consider- able in a laboratory where there is a continual turning off and on of other taps by students. Trials were made with the apparatus in which the dimensions of the parts were varied considerably, but the size and proportions given in the figure were finally segarded as the best for most purposes.A larger size is possibly a little more accurate, owing to the temperature being steadier, but with increase in the size, more of the substance is required, and more of the solvent is used. The accuracy of the volume reading remains proportionally the same whatever the diameter of fhe tube. If the boiling tube C had a diameter much smaller than 1.6 cm., the results obtained were always too high, and this is probably due to the rush of vapour past the thermometer. The vapour is at a lower tempera- ture than the solution, and the thermometer consequently records a temperature slightly below that of the liquid, hence the observed incre- ment is smaller than it ought to be, and the molecular weight calculated from it comes out higher than the true value. The large bulb of the ordinary Beckmann thermometer nearly fills a tube of 1.3 cm.bore. For this reason, a Beckmann thermometer with a particularly small bulb, and graduated only to tenths of a degree, was ordered, but while awaiting its arrival, a cheap paper scale instrument graduated over 50' range in fifths of a degree was wed, and below will be found1198 LUDLAM: A SIMPLE FORM OF LANDSBERGER’S APPARATUS Temp. incre- ment. Volume’ results obtained with it. It is interesting to compare the total cost of this apparatus, using such a thermometer, with the expensive and elaborate contrivances usually considered necessary.The whole of the apparatus as described above can be made by a novice in the art of glass blowing, and, including the thermometer, need only cost a few shillings. Withanaccurate and delicate thermometer having a very small bulb it should be possible to reduce the size of the apparatus so that it occupies no more space in the laboratory than an ordinary melting point apparatus; it could be kept permanently in position, and except for the one weighing, a determination of molecular weight need be no more trouble than a careful melting point determination. Although the apparatus was not designed to give specially accurate results, but rather rapid determination with only slight error, never- theless, comparing the results which have been obtained with it and with the modern Beckmann apparatus both by myself and by students who have had no previous practice with either, it is undoubtedly superior as regards accuracy also.Below are given figures which have been obtained at various times during the last fifteen months, some the result of experiments expressly performed to test the apparatus, the remainder obtained in the ordinary course of laboratory work. The first molecular weight determined by the apparatus was that of propyl benzyl ketone in benzene, and, in addition to reading the volume, the weight of the solvent was also taken : Con- I centra- tion. dl M, Error Per obs. calc. cent. Per 100 Substance, Weight in grams. Propyl benzyl ketone.. 0’260 0’40 13 2 164 162 f1’3 , I I ,, I ,, ( w t .10.79 gms. 1 ,, I 161 1 I , I -0% The internal diameter of the boiling tube in this case was 1.8 cm., and a large bulb Beckmann thermometer which had been set apart for determinations with boiling benzene was used. With a tube of 1.6 cm. diameter, but similar in all other respects, the following results were obtained :FOR DETERMINING THE BOILING POINTS OF SOLUTIONS. 1199 - Error Per cent. f 8 + 10 M'. Error per cent. -___ 93 -1-26 M'. Error per cent. , y .................. Naphthalene ............ Benzophenone ......... Azobenzene ............... >? 9 , ............ ........... Y Y Y , ......... ......... , , .............. 0 *b) - - 0 -55 0.238 - - - Con- centra- tion. Grams M. per 100 , C.C. Weight in grams. Temp. incre- ment. Substance. Volume. --- ' I I- Aniline ..................) ) .................. 0.78 0'10 1.87 1'10 wt. 11 gms. 2.9 C.C. 93 93 With the smallest tube, 1.3 cm. in diameter, a large number of determinations were made with aniline, all of which were much too high. As typical, the result of one of these is given : Wejght in grams. Volume. centra, tion. i Con- Incre- ment. Substance. M. Aniline ................ .I 0 '60 .................. i " ,, 1 $"* 1.4 * 0.80 0.66 0.57 10 C.C. 11'8 6 5 123 119 Another series gave : 5-6 2.23 6'4 1 1.9 wt. 5'63 gms. 1-9 92 97 104 ;; I s: 93 +11 Aniline .................. , y .................. ,) .................. 0'125 2 ) ¶ > * In this case, the thermometer used was the small one mentioned above, graduated The following figures were all obtained by means of the apparatus in fifths of a degree from 50" to 100..as described above in its final form, the solvent being alcohol : - Con- entra. tion. 7.0 6 '4 5% 5 *2 5 *o 3-6 3.5 9.0 7% 7 *2 5.6 5-0 - - M. Weight in grams. Incre- ment. Substance. Volume. 7.5 8.3 9.5 10.2 6 8-2 8.5 6 -2 7'2 7 '6 4.2 4-75 I--- I- 100 99 98 99 139 130 130 188 177 174 179 179 - Aniline ................ 0 *53 * , , ................. y , .................. 1-10 1.00 0.89 0 '82 0 '56 0 '44 0 '42 0-74 0 '68 0.66 0.50 0.45 I * Allowing the solution to cool and then weighing it, the value obtained for M was 92, indicating that the volume reading was not accurate.1200 LUDLAM: A SIMPLE FORM OF LANDSBERGER'S APPARATUS Con- entra- tion. The difficulty in obtaining good determinations of molecular weight increases greatly with.the size of the molecule, and still more if there is an accompanying diminution in solubility. Some substances of this kind were under investigation, and their molecular weights were determined by this method.For example, the additive compounds of dibenzyl ketone and deoxybenzoin with benzylidenem-nitraniline gave the following figures : Ob- M. served '2; -I- 1-7 3-4 2.9 1.7 1.6 2.0 Cz8H,,0,N,. .............. 0.293 0.24 8 -7 1 ,, 10.21 I 10'5 ................. 0.192 0-14 11 *o 459 440) 436 409 404) 436 412 422 12'0 Cz,H,,O,Nz ............... - Error Per cent. + 5 +1 -6 -7 -2 - The last was a most interesting determination, for tbe substance was only sparingly soluble in boiling ;benzene, and the pellet did not dissolve completely.The temperature rose to its maximum value and then remained absolutely constant while the volume was slowly in- creasing. The rise in boiling point was the difference between the boiling points of the pure solvent and of the saturated solution of the substance in it, the latter remaining constant as long as there was solid remaining undissolved. When the volume had increased sufficiently, all the substance dissolved and the readings were taken, the result being quite satisfac- tory. A determination of the same substance in pyridine gave 410, instead of 412 as obtained in this case with benzene. The use of pyridine for molecular weight determinations has been recommended by RoseInnes (Trans,, 1901, 79, 261), but he employed the Beckmann method, and found that owing to the length of time that his corks were subjected t o the action of the pyridine vapour it was necessary to protect them, otherwise they lost their springy nature and shrivelled up into a hard material like wood. Owing to the rapidity of the determination by the method now described, no such difficulty was encountered.The density of boiling pyridine is almost exactly unity, the weight- constant is 29.5, therefore 29.5 was also taken as the volume- constant :FOR DETERMINING THE BOILING POINTS OF SOLUTIONS. 1201 Substance. Deoxybenzoin benzylidene- Succinic acid .................... Metaldehyde ..................... m-nitraniline, C27H,20,N,} Y, ..................... Con. Error Weight. Rise. Volume. centra- Jf. M'. per tion. cent. ------- 0.187 0.185 10.6 1.8 410 422 - 3 0'230 0.40 14 1.7 124 118 + 5 0.11 0.21 12 0.9 131 132 -0'6 0'18 0.30 14'8 1.2 121 ,, -8 Many inorganic salts dissolve in pyridine, but they form compounds with i t in so doing.An interesting observation was made in the case of mercurous chloride. When this salt is boiled with pyridine, it is rapidly decom- posed, giving mercury and mercuric chloride, the latter of which combines with the pyridine, and the compound crystallises out in hard, fine needles. This seems to afford valuable evidence as to the condition of the mercurous chloride molecule. I n Debray's experiments, the mercury was removed from the sphere of action by means of the gold tube cooled by a stream of water. I n Victor Meyer's experiment, it was their different volatility that separated the mercury and mercuric chloride.I n this case, the mercuric chloride is removed by the pyridine, and the dissociation proceeds to completion although the temperature is only 11 ti0. Metaldehyde, so far as I can ascertain, has not been investigated in boiling solutions, but the molecular weight in phenol and thymol has been determined by the cryoscopic method and found to corre- spond to three times the molecular weight of aldehyde, which result is now confirmed by this method, Carbon disulphide was found to be a very convenient solvent for use in this apparatus, and a large number of determinations were made with it. It was first used because it was found necessary to deter- mine the molecular weight of some substances at temperatures lower than that oE boiling benzene or alcohol in order to prevent decomposi- tion.It also possessed the further advantage for our purpose that, like benzene, it was an associating solvent, and would be most likely to give as high a molecular weight for a substance as it was capable of assuming at such a temperature, For instance, Riiber (Be?*., 1901, 34, 1060) obtained the value 264 for the molecular weight of benzoic acid in carbon disulphide, whereas in alcohol he obtained 112, the calculated value for C6H,*C0,H being 122. The ordinary constant for carbon disulphide is 2370 ; dividing by the density at the boiling point (1.225) this gives 1930 as the constant VOL. LXXXI, 4 L1202 for use with volume readings. results obtained with methyl acetoacetate benzylideneaniline : BEWITT AND AULD: THE ACTION OF As an example, we give below the Substance. C,,H,,OJY.., ...... ....... .............,... Con- tion. Weight. ::::: Volume. centra- M. ----- 0.22 14.7 2.26 196 ), 15'0 2-20 177 ), 16.0 2.06 166 ), 16.7 1-98 152 The first of these four determinations took place 35 minutes after introducing the substance. As it did not all dissolve at first it was necessary to wait until sufficient carbon disulphide had collected to dissolve it. The fourth reading of the series was taken 40 minutes later ; decomposition had evidently been steadily taking place. In another series of determinations with the same substance, after 8 minutes the molecular weight was 247. Seven readings were taken in the course of an hour, the last giving a molecular weight 181. Owing to the rapidity with which the solution attains a state of equilibrium, or proceeds on a course of gradual displacement in one direction, and the ease with which the thermometer records the condition of the solution, the apparatus should prove useful in tracing the course of reactions such as the above, UNIVIRSITY COLLEGE, BRISTOL.

ISSN:0368-1645    

DOI:10.1039/CT9028101193

出版商:RSC    

年代:1902

数据来源: RSC

摘要:

1202 BEWITT AND AULD: THE ACTION OF CXX.-The Action of Substituting Agents o n Benzene- axo-6- Naphthol. By J, T, HEWITT and S. J, M. AULD. THE authors recently communicated the results they had obtained in studying the action of bromine on benzeneazo-a-naphthol, and now describe the action of bromine as well as of nitric acid on benzeneano- @naphthol. Some years ago, Margary (GTaxxetta, 1883, 13, 438) added bromine in molecular proportion to a solution of benzeaeazo-P-naphthol in glacial acetic acid; the product obtained melted at 160-161' andStJBSTITUTINa AGENTS ON BENZENEAZO-B-NAPHTHOL. 1203 was recognised as p-bromobenzeneazo-/I-naphthol from the fact that p-bromoaniline was obtained on reduction with stannous chloride and hydrochloric acid, As has frequently happened in cases of this sort, no precautions were taken to avoid the influence of mineral acids, and it was thus of interest to repeat the bromination with addition of sodium acetate, as well as to study the action of nitric acid of various concentrations.Action of nitric Acid. Action of Nitric Acid of sp. gr. 1.15.--Two grams of benzeneazo-/3- naphthol were added to an excess of nitric acid (sp. gr. 1-15). Apparently no change took place in the cold; the mixture was then heated over wire gauze until a vigorous reaction set in, when the flame was withdrawn. The reaction being finished, excess of cold water was added, the solid residue collected, and mashed free from nitric acid. After drying and recrystallisation from benzene, a brownish-red powder was obtained melting at about 168', and obviously consisting of a mixture of substances.The powder proved to be for the greater part soluble in hot dilute sodium hydroxide solution; on cooling, a sodium salt separated in such quantity as to form a thick, crystalline paste, The crystals were collected, again recrystallised from hot water, and decomposed with hydrochloric acid, The substance obtained melted a t 191' (uncorr,) after recrystallisa- tion from hot glacial acetic acid, from which solvent it was deposited as small, pale yellow needles : 0.1479 gave 15.4 C.C. nitrogen at 19' and 745 mm. N= 11.90, C,,H,0SN2 requires N = 11.99 per cent. The identity of the compound with 1 : 6-dinitro-P-naphthol, C,,H,(NO,),*OH, was fully established by the fact that when mixed with a specimen of this substance it did not depress its melting point.The small residue left after extraction with sodium hydroxide was bright red in colour, and after recrystallisation from glacial acetic acid melted a t 241-242' (uncorr.); its identity with p-nitrobenzeneazo-P- naphthol was established by the fact that when mixed with the synthetical product no depression of melting point could be observed. A repetition of the nitration with acid of sp. gr. 1.15 resulted in the production of 0.5 gram of p-nitrobenzeneazo-/I-naphthol and 1 *6 grams of dinitronaphthol from 2 grams benzeneazo-/3-naphthol, The weights refer to crude products ; recrystallisation from benzene was omitted. Practically the whole of the azonaphthol employed is accounted for, about one-fifth of the benzeneazo-P-naphthol employed being nitrated in the benzene nucleus, whilst the other four-fifths are attacked in the naphthol nucleus, the benzeneazo-group in position 1 4 L 21204 HEWITT AND AULD: TEE ACTION OF being replaced by the nitro-group, whilst substitution also takes place in position 6.This result is, however, not inconsistent with initial nitration in the benzene nucleus and subsequent destruction of the nitrobenzeneazo- group. To test the possibility of this explanation, 2 grams of p-nitrobenzeneazo-P-naphthol were heated for some time with an excess of dilute nitric acid of sp. gr. 1-15, On treatment of the product with sodium hydroxide solution in the manner already indicated, it was found that most of the p-nitrobenzeneazo-p-naphthol remained unattacked, and only a small quantity of the 1 : 6Ldinitro-P-naphthol was obtained.The resistance displayed by t h i s nitro-substituted azo- compound towards the action of dilute nitric acid compared with the readiness with which the parent benzeneazonaphtho1 is attacked, shows that 1 :6-dinitro-P-naphthoI must be looked on as a primary product of the action of dilute nitric acid on the latter substance. Action of a Mixture of Concentrated Nitric and Xu@hzcric Acids.- Nitric acid added to a solution of benzeneazo-/3-naphthol in excess of con- centrated sulphuric acid, converts the substance nearly quantitatively into p-nitrobenzeneazo-/3-naphthol. Two grams of benzeneazo-P-naph- thol were made into a paste with 20 C.C. of concentrated sulphuric acid, and 0.76 gram of nitric acid (sp. gr.1.4) mixed with concentrated sulphuric acid gradually added, the mixture being cooled and well stirred. After standing overnight, the mixture was poured into water and the precipitate collected, washed, and dried. The weight of substance obtained was 2.30 grams. Replacement of one hydrogen atom by one nitro-group should have given 2.36 grams. To ascertain how far the product consisted of p-nitrobenzeneazo-P- naphthol, it was warmed with dilute sodium hydroxide solution ; the residue weighed 1-78 grams and melted at 2 3 4 O , but after recrys- tallisation from glacial acetic acid, the melting point was 239' (uncorr.). The hot alkaline filtrate deposited solid matter to the extent of 0.14 gram on cooling; this was not a sodium salt, but melted in the crude condition at 221', and after recrystallisation at 239' (uncorr.), the substance did not depress the melting point of p-nitrdbeneazo-P-naph- thol.On acidification, the final filtrate deposited a tarry mass which was disregarded. Action of Bromine. In Absence of Sodium Acetate.-The bromination of benzeneaso-P- naphthol has been studied by various chemists. Typke (Ber., 1877, 10, 1550) stated that bromine entered the naphthalene nucleus; the result was contradicted by Margary (Gaexetta, 1883, 13, 438), who ob- tained a substance melting at 160-161' which furnished p-bromo- aniline on reduction. Margary conchded that the substance producedSUBSTITUTING AGENTS ON BENZENEAZO-P-NAPHTHOL. 1205 was p-bromobenzeneazo-P-naphthol, a result confirmed by Zincke and Bindewald (Ber., 1884, 17, 3032), who, however, gave the melting point as 167-1 68'.Finally, Bamberger synthesised p-bromobenzene- azo-/?-naphthol from p-nitrosobromobenzene, /?-naphthol, and hydroxyl- amine, giving the melting point as 172-173' (Ber., 1895, 28, 1222). We find that if finely powdered benzeneazo-/3-naphthol be suspended in ten times its weight of glacial acetic acid and brominated in the cold with the calculated quantity of bromine dissolved in acetic acid, p-bromobenzeneazo-P-naphthol is obtained in practically quantitative amount ; aftev recrystallisation, the substance melts a t 170' (uncorr.). The identity of the substance was confirmed by mixing with the syn- thetical compound, when no depression of melting point was observed.The formation of p-bromoaniline on reduction was also put beyond doubt by distilling the reduction mixture, after rendering alkaline, in a current of steam, and benzoylating the base contained in the distil- late. The recrystallised benzoyl derivative contained bromine and melted at 200° (uncorr. j. In Presence of Sodium Acetate.-Experiments mere next made on the action of bromine in preseiice of sodium acetate. At the ordinary temperature, bromine appears to be without action on a solution of benzeneazo-@naphthol in glacial acetic acid if sodium acetate has been added. Even on boiling, reaction, if it takes place at all, is extremely limited. A t 165-170O under pressure, the bromine is used up in half- an-hour. On pouring into cold water the product of the action of 3.5 grams of bromine on 5 grams of benzeneazo-@naphthol dissolved to- gether with 3.5 grams of fused sodium acetate in 50 C.C.of gIacial acetic acid, a brown tar was deposited which liquefied completely below looo. Attempts to separate the mass into its constituents were extremely un- satisfactory ; a small quantity of a crystalline powder was obtained on one occasion by dissolving the mass in ethyl acetate and adding acetic acid, the excess of ethyl acetate being removed by distillation. The substance melted a t about 260° (uncorr.) and contained bromine : C = 65.8 ; H = 3.5. 0.0818 gave 0.1936 CO, and 0.0261 H,O. 0.0810 ,, 0.0231 AgBr. Br= 12.1. 0,1068 ,, 0-0308 AgBr. Br = 12-3 per cent. The substance is evidently not a monobromobenzeneazo-&naphthol, which would require 24.4 per cent.of bromine ; probably it is formed by the condensation of 2 mols. of the azo-compound. The quantity of the substance produced is so extremely small, that, whatever its structure, it can have but little bearing on the constitution of benzene- azo-P-napht hol.1206 HEWITT AND AULD : BENZENEAZO-&NAPHTHOL, Bromobenxeneaxo-/3-nap?~tho Is. During the progress of the work described above, the three bromo- benzeneazo-/I-naphthols were prepared for purposes of comparison, and further characterised by conversion into acetyl or benzoyl derivatives. o-Bromo6enxene~z0-P-n~~htrllol was prepared in the customary manner ; it melts at 165O. It is best obtained by recrystallisation from boiling benzene, from which it is deposited as small, brownish plates; it dissolves easily in carbon disulphide, and is taken up fairly readily by acetic acid, acetone, ethyl acetate, ether, or light petroleum.Its soh- bility in alcohol is slight : 0.1472 gave 0.0847 AgBr. The acetyl derivative separates from glacial acetic acid as small, 0.1368 gave 0.0698 AgBr. Br = 24.49. C1,Hl10N2Br requires Br = 24.43 per cent. brown crystals with a bronzy lustre and melts at 157' : Br = 21.94. C,,H,,O,N,Br requires Br = 21.69 per cent. m-Bromobenzeneaxo-~-naphthot, recrystallised from benzene, forms broad, red needles exhibiting a beautiful reflex; it melts at 172' : 0.2239 gave 17.0 C.C. nitrogen at 20" and 737 mm. 0.2460 ,, 0.1414 AgBr. Br= 24.22. N = 8.61. Cl,Hl10N2Br requires N = 8-59 ; Br = 24.43 per cent. The acetyl derivative melts at 88O:af ter recrystallisation from glacial acetic acid : 0.3012 gave 20.5 C.C. nitrogen a t 20' and 759 mm. The benzoyl derivative is a beautiful, dark red substance, crystallising 0.2176 gave 12.0 C.C. nitrogen a t 22O and 770 mm. N = 7.72. C,,H,,O,N,Br requires N = 7.48 per cent. in obliquely terminated prisms and melts at 159O : N = 6.45. C23H1502N2Br requires N = 6.49 per cent. p-Bromobenxeneaxo-/3-naphthoI has already been described ; the melt - ing point we observed for the substance agreed with that given by Bamberger. The acety2 derivative forms beautiful, dark red needles and melts at 136' : 0.1784 gave 0.3813 CO, and 0.0598 H,O. C = 58.29 ; H = 3.68, Cl,Hl,0,N2Br requires C = 68-53 ; H = 3.52 per cent.THE CONDENSATION OF DIMETHYLAMINOBEKZALDEHYDE. 1207 The benxoyl derivative melts at 157*, and separates from glacial 0,2344 gave 0°1012 AgBr. Br = 18.41, C2,HI50,N2Br requires Br = 18*05 per cent. acetic acid as very dark red needles : EAST LONDON TECHNICAL COLLEGE.

ISSN:0368-1645    

DOI:10.1039/CT9028101202

出版商:RSC    

年代:1902

数据来源: RSC

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THE CONDENSATION OF DIMETHYLAMINOBEKZALDEHYDE. 1207 CXX1.-The Condensation of D.rmethylam.inobenxalde- hyde with p-Naphthol. By JOHN THEODORE HEWITT, ALFRED JOHN TURNER, B.Sc., and SIDNEY WALLACE BRADLEY. THE condensation of aldehydes with P-naphthol has been studied by various chemists with the general result that one molecule of the aldehyde unites with two molecules of the naphthol to give derivatives of the type R*CH(C,,H,*OH),, or corresponding internal anhydrides, R*CH(C,,H,),O. Substances of the first series have been obtained from formaldehyde (Hosaeus, Ber., 1892, 25, 3213; Abel, Ber., 1892, 25, 3477), 0- and m-nitrobenzaldehydes (Zenoni, Gaxxetta, 1893, 23, 2 16), and benzalde- hyde (Hewitt and Turner, Ber., 1901, 34, 202), whilst internal anhy- drides have been produced from P-naphthol and acetaldehyde and benzaldehyde (Claisen, Annalen, 1887, 237, 270), the three nitro- benzaldehydes (Zenoni, Zoc.cit.), and various other aromatic aldehydes (Rogoff, Ber., 1900,33, 3535). Considerable interest attaches to the compounds of the anhydride type, since they may be regarded as leuco-derivatives corresponding with carboxonium salts, and the authors were engaged in a study of their oxidation products when they were anticipated by Werner (Beg*., 1901, 34, 3300), who published an account of oxonium salts derived by the action of oxidising agents on phenyldinaphthylene oxide, c,H,*cH<~~o~~>o. C H 10 6 In the present communication, the condensation of P-naphthol with dimethylaminobenzaldehyde is described. It is a pleasant duty for the authors to record their best thanks to Geb.-Medizinalrath Professor1208 HEWITT, TURNER, AND BRADLEY: THE CONDENSATION OF Ehrlich for the kindness he has show'n in placing a considerable quantity of the latter substance in a pure condition at their disposal.Conndemation of Dimethylaminobenealdehycle with P-Naphthol in Cold Acetic XoZution.-If a glacial acetic acid solution of dimethylamino- benzaldehyde (1 mol.) and P-naphthol (2 mols.) be acidified with con- centrated hydrochloric acid (2 mols.) and allowed to stand at the ordinary temperature for a week, crystals are deposited. When collected, washed, and then recrystallised from a large quantity of glacial acetic acid, small, hard, brilliant prisms are obtained, which for analysis were dried a t 110': - 0-1296 gave 0.3615 CO, and 0.0658 H,O, 0,1227 ,, 3.3 C.C.nitrogen a t 17' and 756 mm. N=3*07. C = 76.07 ; H= 5.64. 092006 ,, 0.0659 AgCl. C1= 8.13. C,9H2,0,NCl requires C = 76.36; H = 5.76; N = 3.08; C1= 7.78 per cent. On heating, the substance darkens somewhat at about -150' and finally melts a t 215" with decomposition. Although the crystals are practically colourless, the hot concentrated solution in glacial acetic acid appears blue; after cooling, when the greater portion of the substance has been deposited, the shade is red, whilst a green fluorescence is observed. Probably the coloration is to be ascribed to limited oxidation, the direct product being the hydrochloride OF a, base, (CH,),N*C,H,* CH( C,,H,-OH),. A specimen of the chloride which had been kept for some months exhibited a lower melting point.As it was possible that the result might be due to a partial formation of an anhydride a t the expense of the hydroxyl groups whereby, owing to mixture, the original melting point would be lowered, the salt was dissolved in glacial acetic acid, an excess of concentrated hydrochloride acid added, and the solution boiled for a few hours under reflux. The boiling solution was filtered hot and the crystals deposited on cooling were collected and dried. The melting point was then found to be 257'; the substance gave on analysis numbers which proved the loss of a mol. of water: 0,1469 gave 0.4282 CO, and 0.0777 H,O. 0.1450 ,, 3.97 C.C. nitrogen at 17' and 758 mm. N=3*14. C = 79.49 ; H = 5.87. C,,H,,ONCl requires C = 79.50 ; H = 5.54 ; N = 3.21 per cent.Condensation of DimetI~yZ~minobenxaldei~~~e with P- Naphthol in Hot Xolutiom-Salts of the base C,,H230N are immediately obtained if the condensation is carried out in hot instead of i n cold solution. The following method of preparation is satisfactory both in point of yield and purity of product. Twenty grams of P-naphthol and 10 grams of dimethg laminobenzaldehyde are dissolved in 120 C.C. of glacial acetic acid, Twenty grams of strong sulphuric acid diluted with 10 c.cDIMETHYLAMINOBENZALDEHYDE WITH ,&NAPHTHOL. 1209 of water are next added and the mixture boiled for one hour. More dilute sulphuric acid is added and then hot water until a specimen shows that a copious crystallisation takes place on cooling; the bulk OF the solution is then cooled and the crystalline mass collected, well washed, digested for some time with hot potassium hydroxide solution, filtered off, well washed, and dried. For purification, the substance is recrystallised several times by solution in boiling pyridine and addition of light petroleum; it then separates on cooling in a beautifully crystalline condition.It is, however, remarkable that the crops obtained from the first crystallisation, although appearing to consist of a practically pure substance, melt-at 194-197' (199-202O corr.), and give numbers on analysis too low in carbon, If the substance be recrystallised subsequently from boiling xylene, it is obtained as colourless prisms melting a t 2 14-215' (corr.), and furnishing the following results on analysis : 0.2321 gave 0,7354 CO, and 0.1223 H20.0.2248 ,, 6.47 C.C. nitrogen at 5' and 756 mm. N=3.47. C = 86.42 ; H = 5*85. C,,H,,ON requires C = 86.72 ; H = 5.79 ; N = 3.50 per cent. The substance is very easily soluble in pyridine bases whether hot or cold, boiling aniline dissolves the compound readily, but it is not very soluble in the cold solvent, in alcohol it is very sparingly soluble; hydrocarbons of the benzene series dissoive it fairly easily, especially if hot, hence xylene on account of its higher boiling point makes a better solvent than benzene. Acetic acid if hot dissolves the base with ease, probably in the form of an acetate. Although salts are formed with many acids, the latter do not form good solvents, as most of the salts are practically insoluble in water.The chloride, C,,H2,0N,HCl, is obtained either by passing dry hydrogen chloride into a benzene solution of the base, or more easily by dissolving the base in boiling glacial acetic acid and adding fuming hydrochloric acid until the beginning of a disturbance. The chloride separates as a colourless, crystalline powder consisting of obliquely terminated prisms melting at 257-260'. The substance is thus seen to be identical with the chloride obtained by boiling dinaphthol- dimethylaminophenylmethane hydrochloride with a mixture of acetic and hydrochloric acids, 0.1455 gave 0.0470 AgC1. C1= 7.98. C,,H,,ONCl requires C1= 8.09 per cent. The pZatinichZoride, (C,gH,,ON),,H,PtCIG, was prepared by adding a solution of platinum tetrachloride in- concentrated hydrochloric and acetic acids to a solution of the base in ten times its weight of acetic acid.The substance separated in-small, yellow, rhomboidal tablets melting at On analysis :1210 HEWITT, TURNER, AND BRADJ,EY: THE CONDENSATION OF 256'. following result on analysis : 0,1543 gave 0.0246 Pt. The suZpiuxlte, C,,H,,ON,H,SO,, obtained by the action of sulphurio acid in excess, and purified by recrystallisation from a mixture of alcohol and sulphuric acid, was obtained as small, colourless needles melting at 231-232O with decomposition. The melting point depends somewhat on the rate of heating, and may vary by several degrees : It is very sparingly soluble in all solvents and furnished the Pt = 15.95. (C,,H,,0N)2,H2PtCl, requires Pt = 16.07 per cent.0,1046 gave 09702 CO, and 0.0533 H,O. 0-1649 ,, 0.0764 BaSO,. H,SO,= 19.46. C?29N,30N,H2S0, requires C = 69.67 ; H = 5.16 ; H,SO, = 19.24 per cent. The picrate, C2,H,,0N,C6H307N3, separates on mixing solutions of the constituents in benzene. The salt obtained was at first thought not to be homogeneous, since besides larger well-defined prisms, tufts of small needles were obtained. On heating the solution to the boil- ing point, it was found that the latter went into solution and separated out on slow cooling in the prismatic condition. Since the two crops of crystals exhibited the same melting point, there can be no doubt as to the uniformity of the substance ; the following analysis was carried out with a mixture of the two crops : C = 70.50 ; H = 5.66.0.1042 gave 0.2534 CO, and 0.0428 H,O. C= 66.32 ; H = 4-56. C,,N,,O,N, requires C = 66-62 ; H= 4.16 per cent. The salt forms shining, yellow prisms melting at 194-196'. The methiodide, C,,H,,ON,CH,I, is produced by warming the base for some time with an excess of methyl iodide. At first the base dis- solves completely ; soon small, pale yellow crystals begin to separate, which, after collection, washing with methyl alcohol, and drying in a vacuum over lime melt a t 226-227". 0.1882 gave 0*0807 AgI. Attemptcl at Oxidation.-From the constitution of this base, it seemed I = 23.19. C,oH,,ONI requires I = 23.35 per cent. very probable that a carbinol would result on oxidation :DIMETRYLAMINOBENZALDEHYDE WITH &NAPHTHOL. 121 1 This should correspond to salts of one of the following types : A Experiments made in this direction showed that the substance was very resistant to oxidising agents, a result already foreshadowed by the stability of the platinichloride.Action of Ferric Chloride.-One gram of solid ferric chloride dis- solved together with 3 C.C. of fuming hydrochloric acid in an excess of glacial acetic acid, was added to a boiling solution of the base in glacial acetic acid. After heating for 1+ hours in a reflux apparatus, the solution was poured into an excess of dilute hydrochloric acid ; the crystalline precipitate thereby produced was collected, well washed and dried. The melting point of the substance so obtained was 259-260' ; when mixed with the hydrochloride of the original base, no depression of melting point was observed.Action of Peroxides.-On dissolving the base in hot acetic acid and adding sidphuric acid and lead or manganese dioxide, no oxidation to a colouring matter was effected; the base after recovery melted a t 208' (uncorr.), and did not depress the melting point of the substance prepared directly. Action of Bromine.--Bromine was also employed on account of its greater activity. Five parts of the base were dissolved in glacial acetic acid, the solution well cooled, and 2 parts of bromine diluted with acetic acid added gradually. A precipitate was obtained melting at 196' (uncorr.) ; this was collected and dried : 0.1638 gave 0.1070 AgBr. The salt being somewhat coloured, it was thought probable that an Br = 27.80. C29H230NBr, requires Br = 28-50 per cent. oxonium compound : C H C6H,*C<CIOH6>0 Br , HBr ( CH,) 10 6 had been produced; since, however, alkali only removed a portion of the bromine, and the base obtained contained 72.2 per cent. of carbon, it was evident that only one bromine atom was present in an ionisable condition, the other atom having replaced hydrogen in1212 RUHEMANN: THE ACTION OF ETHYL either the benzene or one of the two naphthalene nuclei. Contrary to expectation, the conclusion seems to be inevitable that xanthen derivatives obtained from dimethylaminobenzaldehyde show little or no tendency to pass into carboxonium compounds on oxidation, EAST LONDON TECRHICAL COLLEGE.

ISSN:0368-1645    

DOI:10.1039/CT9028101207

出版商:RSC    

年代:1902

数据来源: RSC

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1212 RUHEMANN: THE ACTION OF ETHYL CXXIL-The Action of Ethyl Chloyofumarate on Monoalkylmalonic Esters. By SIEUFRIED RUHEMANN. THIS investigation was undertaken with the view of preparing alkyl derivatives of aconitic acid, and to study them on the same lines as aconitic acid itself. Although the action of ethyl chlorofumarate on the sodium derivative of ethyl malonate does not yield ethyl carboxy- aconitate but ethyl trimethylenetetracarboxylate, nevertheless such a transformation of the unsaturated grouping into trimethylene com- pounds is excluded if, instead of ethyl malonate, its monoalkyl deriv- atives are used. Their sodium compounds react, indeed, with ethyl chlorofumarate according to the equation : It*CNa(CO,Et), + CO,Et*CCl:CH*CO,Et = R*C(CO,Et),*C( C0,Et): CH*CO,Et + NaCI, but the yield of the homologues of ethyl carboxyaconitate is small.The quantity depends on the nature of the alkyl group in the substi- tuted malonic ester, and decreases as the size of the radicle increases. Thus, on treatment of ethyl chlorofumarate with ethyl sodiomethyl- malonate, 50 per cent. of ethyl methylcarboxyaconitate are produced, but the yields are as small as 6 per cent. on using the phenyl or benzyl derivatives of malonic ester. As yet, I have only examined in detail the hydrolysis of ethyl phenylcarboxyaconitate, and have found that a substance of the formula C,,H,O, is formed which is the anhydride of a dicarboxylic acid. It is neutral t o litmus, it melts on heating with water to an oil which slowly dissolves, giving an acid solution; from this, on cooling, the greater part of the anhydride separates out again. The alkaline solu- tion of the substances is not attacked by potassium permanganate and the anhydride does not form an additive compound with bromine.These facts lead to the conclusion that the product is not an unsatur- ated compound, but a derivative of trimethylene. The following twoCHLOROFUMARATE ON MONOALKYLMALONIC ESTERS. 1213 formula are the only ones possible which agree with its mode of forma- tion from ethyl phenylcarboxyaconitate : (1) A C,H,* C-CO (’) H2C--CH* GO \/ 0 C,H,*CH (1) (3)H$!--$!H(2) /\ >o. (3) (2) ( l ) oc co The result of the action of sodium amalgam on the anhydride proves formula (2) to be correct. Under the influence of the reducing agent, the anhydride, besides being transformed into the corresponding acid, unites with two atoms of hydrogen :and yields a dicarboxylic acid identical with Zelinsky and Buchstab’s s-phenylmethylsuccinic acid, C6H5*CH(C0,H)*CH(CH,)*C02H (Ber., 1891, 24, 1876). The form- ation of this acid from the anhydride C,,H,O, can only take place with a compound of formula (2).I t further follows that the trimethylene ring does not open up between the carbon atoms 1 and 2, as might be expected, but between the atoms 1 and 3. EXPERIMENTAL. The method which z‘ have used for the preparation of the homologues of ethyl carboxyaconitate is as follows. The monoalkylmalonic ester (1 mol.) is mixed with a solution of sodium (I at.) in absolute alcohol, and then ethyl chlorofumarate (1 mol.) is added.The mixture becomes warm and turns a deep yellow or brown; it is heated on the water- bath for about 6 hours, the alcohol distilled off as far as possible, the residue poured into water, and the solution acidified with dilute sulph- uric acid and extracted with ether, The oil which remains after evaporation of the ether is subjected t o fractional distillation in a vacuum. The larger portion passes over at a low temperature and is a mixture of the unchanged esters; from the portion of higher boiling point, the product of the reaction is obtained pure after 2 or 3 distil- lations. Ethyl Methylcarboxyaconitate, CH, C(C02*C2H5)2*C( GO,- C,H,) : CH*C?0,*C2H5. This ester is formed from ethyl methylmalonate and ethyl chloro- fumarate in the manner described above; it is a yellow oil which boils at 302-204O under 16 mm, pressure.On analysis : 0.2004 gave 0.4088 CO, and 0.1260 H,O. C= 55.63 ; H== 6.98. C,,H,,O, requires C = 55.81 ; H = 6.98 per cent.1214 RUHEMAPL”: THE ACTION OF ETHYL Ethyl Ethylcarboxyaconitate, C2H5* C (CO,. C,H,),*C( CO,*C,H,) :CH*CO,* C,H,. The yield of this substance from ethyl ethylmalonate and ethyl chlorofumarate is very small; it is a viscous oil, which distils at 205-207O under 14 mm. pressure, 0.2015 gave 0.4190 CO, and 0*1280 H,O. C- 56.71 ; HI 7.15. CI7H,,0, requires C = 56.98 ; H = 7-26 per cent. On analysis : Ethyl Benxy Ecarbox yacon;t ate, C,H,* CH,* C( C02*C2H,),~C(C0,*C2H5): CH* CO,*C,H,. On boiling the mixture of ethyl benzylmalonate and ethyl chloro- fumarate with a solution of sodium in alcohol, the liquid turns blue, The quantity of ethyl bensylcarboxyaconitate which is.formed amounts to 6 per cent.The yield is about the same, if, instead of ethyl chlorofumarate, ethyl acetylenedicarboxylate is heated with ethyl benzylmalonate and dry sodium ethoxide for several hours on the water-bath, The product of the reaction is a very viscous oil which boils at 245-246’ under 15 mm. pressure. On analysis : 0.2016 gave 0.4633 CO, and 0.1197 H,O. C = 62.67 ; K = 6.60. Alcoholic potash readily acts on the ester ; a yellow solid is precip- itated, and the liquid turns deep red. On adding dilute sulphuric acid t o the aqueous solution of the product of hydrolysis, carbon dioxide is evolved, and the organic acid separates as a very viscous oil.I have not obtained it in a pure state, but the following analysis of the silver salt, prepared from the oil, and dried at loo’, indicates it to be a tricarboxylic acid : C2,H,,0, requires C = 62.86 ; H = 6.67 per cent. 0.2773 left, on ignition, 0,1515 Ag. Ag=54*63, C1,H,OGAg, requires Ag = 55-38 per cent. Ethyl P~snylcarboxyaconitate, C6H,*C(C02~C,H,),-C(C02*C2H,):CH*C0,*C,H,, Ethyl phenylmalonate, which is required for the formation of the ester, was prepared, according to W. Wislicenus’ directions (Ber., 1894, 27, 1091), by heating ethyl phenyloxaloacetate, the product of the action of sodium ethoxide, on a mixture of ethyl oxalate and ethyl phenylacetate ; its boiling point was found to be 158-150’ under 10 mm. pressure, as compared with 170-17Z0 under 14 mm.pressure given by Wislicenus. The ester, on treatment with ethyl chlorofumarate andCRLOROFUMARATE ON MONOATJKYLMALONIC ESTERS. 1215 a solution of sodium in absolute alcohol, as in the previous cases, yields e thy1 phenylcarboxyaconitate. On analysis : 0*2195 gave 0.4992 CO, and 0.1270 H,O. C21H,G0, requires c = 62.07 ; I3 = 6.40 per cent. With the view of improving the yield of this ester, which is only 6 per cent., I have modified the action between ethyl phenylmalonate and ethyl chlorofumarate by using absolute ether and dry sodium ethoxide. The ethoxide dissolves and the solution turns deep red. After allowing to stand for a day, evaporating the ether and fraction- ating the oil which remains behind, the same result as in the previous case is obtained.Nor is the yield increased if, instead of ethyl chlorofumarate, ethyl acetylenedicarboxylate is mixed with ethyl phenylmalonate and the mixture heated with dry sodium ethoxide on the water-bath. The fact that in the first method the alcoholic solution becomes neutral, although a quantity of the esters of phenyl- malonic and chlorofumaric acids remains unaltered, seems to indicate that the ethoxide forms an additive compound with ethyl phenyl- carboxyaconitate. This view is in harmony with the following result : on distillation of the products of the reaction, a small quantity of an oil passes over at a temperature beyond the boiling point of ethyl phenylcarboxyaconitate, whilst a tarry residue remains behind in the flask. Anhydride of Phen yltiaimeth ylenedicarboxylic Acid, C= 62*02; H=6*42.The hydrolysis of the ester is complete after 2 hours' boiling with alcoholic potash on the water-bath, The alcohol is distilled off and the residue dissolved in water; on adding an excess of dilute sulphuric acid to the solution, carbon dioxide is evolved and a solid gradually separates out, The filtrate from it, on extraction with ether, furnishes a further crop of the substance. It crystallises from dilute alcohol in colourless needles which melt at 99'. On analysis : 042058 gave 065297 CO, and Oa0830 H,O. C,,H,O, requires C = 70.21 ; H = 4'26 per cent, The rsubatance is readily soluble in alcohol, ether, or benzene, and these solutions are neutral to litmus; on boiling with water, it melts and very slowly dissolves, yielding an acid solution from which, on cooling, the larger portion of the original substance crystalliaes.These facts indicate that the compound is the anhydride of n dicarb oxylic acid and that this acid is transformed into its anhydride with the greatest ease. The salts of the acid, however, are stable; I have examined those with silver and lead. C = 70.19 ; H= 4.48,1216 THE ACTION OF ETFIYL CHLOROFDMARATE. The siZver salt is obtained as a white precipitate by boiling the anhydride with dilute ammonia and adding silver nitrate to the soh- tion thus produced. It is stable to light, and can be dried at 100'. On analysis : 0.3640 left, on ignition, 0.1870 Ag. Ag=51*37. The lead salt is formed as a crystalline solid by dissolving the anhydride in boiling water and adding lead acetate.For analysis, it was washed with water, then with alcohol, in order to free it from unaltered anhydride, and dried at looo : C1,H80,Ag2 requires Ag = 51.43 per cent. 0.3920 gave 0.2875 PbSO,. P b = 50.12. C,,H,O,Pb requires P b = 50.36 per cent. s-Phenylmethylsuccinic Acid, C,H5*CH(C0,H)*CH(CH,)*C0,H. The reduction of the compound C,,H,O, is effected in alkaline solution by sodium amalgam. The anhydride is insoluble in cold potash, but on boiling it gradually dissolves. The solution is allowed t o assume the temperature of the room, and is then agitated with an excess of sodium amalgam (24 per cent.). After standing overnight, the liquid is decanted from the mercury and mixed with an excess of dilute sulphuric acid, when a colourless substance gradually separates.This is readily soluble in alcohol or ether, but only sparingly so in boiling water, from which, on cooling, it crystallises in plates melting a t 192-193O. On analysis : 0.2033 gave 0.4743 GO, and 0.1085 H20. C= 63-62 ; H= 5.92. As has been mentioned in the introduction, this substance is s-phenylmethylsuccinic acid. Zelinsky and Buchstab (Zoc. cit.) obtained it by hydrolysing the product of the interaction of ethyl sodiocyano- acetate and ethyl a-bromophenylacetate with potassium hydroxide and heating the tricarboxylic acid thus formed with dilute sulphuric acid. The acids are identical because their melting points are the same and because they are transformed into anhydrides with identical properties. The anhydride is formed from the acid at the temperature of the fusing point.Zelinsky and Buchstab distilled it under the ordinary pressure, when it passed over between 310' and 320'; I find that, on heating in a vacuum, it distils at a constant temperature of 184O under 10 mm. pressure as a colourless oil which, like Zelinsky and Buchstab's anhydride, is transformed back into the dicarboxylic acid by boiling water. I have, moreover, examined the following salts of g-phenylmethylsuccinic acid, C1,Hl2O, requires C = 63.46 ; H = 5.77 per cent.SOLUBILITY OF MANNITOL, PICRIC ACID, AND ANTHRACENE. 1217 The silver salt is precipitated by adding silver nitrate to the neutral solution of the acid in ammonia; it is not changed by light or by dry- ing at 1009 On analysis : 0.3910 left, on ignition, Og2000 Ag. Cl1H1,O,Ag, requires Ag = 5 1.1 8 per cent. The bad salt is formed as a white precipitate, insoluble in water, on 0.2680, dried at looo, gave 0.1970 PbSO,. Pb = 50.23. Ag=51*15. mixing aqueous solutions of the acid and lead acetate. On analysis : C,,H,,O,Pb requires Pb = 50.12 per cent. The barium salt separates in colourless needles on adding barium chloride to the neutral solution of the acid in ammonia. The salt, when dried a t looo, contains 2 mols. H,O, as indicated by the follow- ing determination : 0-2215 gave 0,1356 BaSO,. Ba= 35.96. The barium salt, although sparingly soluble in water, slowly crys- tallises from its aqueous solution. The solution has to be evaporated until the salt begins to come down, and the process of concentration and filtration frequently to be repeated when this mode of purification is adopted. C,,H1,0,Ba,2H,0 requires Ba = 36.14 per cent. GONVILLE AND CAIUS COLLEGE, CAMBRIDGE.

ISSN:0368-1645    

DOI:10.1039/CT9028101212

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年代:1902

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SOLUBILITY OF MANNITOL, PICRIC ACID, AND ANTHRACENE. 1217 CXIII.-The Solubility of J4annitoZ, Picric Acid, and A nthracene. By ALEXANDER FINDLAY. IN connection with another investigation dealing with a method of extrapolating the solubility curve of a substance, it became necessary for me to determine the solubilities of one or two substances at differ- ent temperatures and in different solvents. The substances and solvents chosen were: mannitol in water, picric acid in water and in benzene, and anthracene in benzene. It has recently been shown by the author (Proc. Roy. Xoc., 1902, 69, 471) thatif the solubility of a substance be determined at two, or, better, at three different temperatures lying fairly wide apart, the entire solubility curve can be calculated with a fair degree of accuracy by comparison with a known solubility curve (6 comparison curve '), by VOL.LXXXI. 4 M1218 FINDLAY: THE SOLUBILITY OF means of the relationship T,/Z”, = T2/P2 + c(t‘ - t), where T./T’, and F2/T2 are the ratios of the absolute temperatures at which the two substances have equal solubilities, c is a constant, and t’ and t the temperatures a t which one of the substances has the two values of the solubility in question. This relationship, which is analogous to that shown by Ramsay and Young to hold for the vapour pressures of substances (Phil. Mag., 1886, [v], 21, 33), may also be made use of even when the solvents are different. The solubility of the above- substances was determined at several temperatures between 25’ and 60’. From the values so obtained, the solubility at temperatures below 25’ and above 60’mas calculated by comparison with known solubility curves in the manner previously given by the author (loc.cit.). From theoretical considerations,* it is best to choose as the comparison curve one which is similar in form to the solubility curve of the substance in question. For the purpose of extrapolating the solubility curves of mannitol and of picric acid in benzene, the solubility curve of potassium chlorate, constructed according to the values of the solubility obtained by Gay-Lussac (Arm. Chim. Phys., 1875, [v], 11, 314) and by Tilden and Shenstone (Trans., 1879, 35, 345) was employed as comparison curve. The solubility curve of CaCrO,,$H,O as determined by Mylius and v. Wrochem (Bey., 1900, 33, 3639) was employed in order to calculate the solubility curve of picric acid in water, and the latter curve then used as the comparison curve for extrapolating the solubility curve of anthracene.Although, therefore, only those values of the solubility lying between the above limits of temperature can be regarded as experimentally determined, it appeared to be worth while to give the extrapolated values as well, since they may be taken as sufficiently accurate for all practical purposes at least. The figures given in the following tables were read from curves con- structed according to t6e above method, and the solubility is expressed both in grams of substance in 100 grams of solvent (percentage solu- bility), and as number of gram-molecules or moles of substance in 106 moles of solvent (percentage molar solubility).The vdues enclosed in brackets were determined experimentally. Solubility of Mannitol ilz Water, No complete set of solubility determinations has been made in the case of mannitol, but the following values of the percentage solubility have been found at isolated temperatures: 15.6 per cent. at 18’; 18.5 per cent, at 23‘ (Bertbelot, Ann. Chim, Phya., 1856, [%I, 47, * A theorotical discussion of the above relationship will appear ahortly in the Zeihchr~t far physikalische Chemie.kiNNiTOL, PlCRIC ACID, AND ANTaRACENE. 1219 361); 13.0 per cent. a t 14O (Krusemann, Bw., 1876, 9, 1467) ; 16.07 per cent, at 16.5O (Erlenmeyer and Wanklyn, Trans., 1862, 15, 456). The following are the values of the solubility determined experi- mentally and calculated by the above method : Percentage solubility.Temperature. Percentawe molar solubi'li ty. 0" 6 10 15 20 (24 ' 5 ) 25 30 (35.8) 40 50 (50.8) 60 70 80 90 100 7 *59 9-41 11.63 14.38 17-71 (20.96) 21 *39 25 '40 (29 -93) 35-40 47'01 (46'69) 60.01 74.50 91-50 110.8 133'1 0.75 0.93 1.15 1-42 1.75 (2.07) 2-11 2'51 (2'96) 3.50 4 *65 (4'63) 5 94 7-35 9 '04 10-96 13.17 Pic& Acid in Water. The solubility of picric acid in water was determined many years ago by Marchand (J. pr. Chem., 1855, 64, 91). As, however, the method employed was precipitation by strong acids, it appeared advis- able to redetermine the solubility by titrstion with barium hydroxide, using lacmoid as indicator. The values obtained are practically identical with those found by Marchand between the temperatures of 15O and SOo, but the value of the solubility at 5*, as given by Marchand, is almost certainly too low, The solubilities as newly determined and calculated are as follows : Temperature.Percentage solubility. 0" 6 10 15 30 25 (28.5) 1-05 1.07 1 . l o 1.16 1 -22 1.37 (1.42) Percentage molar solubility. 0 ,082 0 '084 0 *086 0'081 0'096 0.108 (0 -11 2) 4 M 21220 SOLUBILITY OF MANNITOL, PICRIC! ACID, AND ANTHRACENE. Temperatare. Percentage solubility. 30 (38.4) 40 (44'6) 50 60 70 80 90 100 (58.7) 1 *55 ( 1 -90) 1 '98 (2.17) 2 '53 (3.14) 9.17 3 '89 4 '66 5'49 6 -33 Percentage molar solubility. 0'122 (0.149) 0-156 (0.170) 0.199 (0.247) 0-249 0.306 0'366 0.432 0'497 Picric Acid in, Benzene. The only statement I have been able to find regarding the solubility of picric acid in benzene is that at the ordinary temperature benzene dissolves 8-10 per cent.of picric acid (Beilstein). The following are t h e newly determined and calculahed values : Temperature. 5" 10 15 20 25 (26 '5) 35 (38.4) 45 55 (58.7) 65 75 Percentage molar soliibili ty Percentage solubiiity. 3 9 0 5 '37 7.29 9 '56 12-66 (13 '51) 21 -38 (26.15) 33'57 50'65 (58'42) 71.31 96-77 1'26 1'83 2.48 3-25 4 '30 (4'60) 7 *26 (8'8s) 11'40 17'21 (19 -8.7) 24.20 3292 Anthracene in Benzene. According to Versmann (Jahresber,, 1874, 423), the solubility of anthracene iri benzene is 1.661 per cent. at 15O, a value rather greater than that which I have found. The complete solubility curve is re- presented by the following figures :McCRAE : DI-SEC.-OCTYL TARTRATE. 1221 Temperature. 5" 10 15 20 25 30 40 (44 '6) 50 60 70 80 (26%) (35'4) Peroen tage solubility. 0.979 1,118 1.532 1'830 (1'951) 2-175 (2 -7 7 3) 2-987 (3'368) 3.928 4.941 6.041 7-175 ' 1'296 Percentage molar solubility. 0.429 0-491 0.567 0.673 0'803 (0.856) 0.954 (1 *213) 1-312 (1'473) 1,727 2.164 27349 3-143 CHEMICAL DEPARTMENT, UNIVEKSITP COLLEGE, LONDON.

ISSN:0368-1645    

DOI:10.1039/CT9028101217

出版商:RSC    

年代:1902

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McCRAE : DI-SEC.-OCTYL TARTRATE. 1221 CXX1V.-Di-See. - Octyl Tartrate and Di-see. - Octyl Bibenxo ylt urtra f e. By JOHN MCCRAE. IT has already been explained (Trans., 1901, 79, 1103) that by the action of an acid chIoride on a tartaric ester containing alkyl groups high in the series it was anticipated that it would be easy to obtain- a monoacyl derivative. When one ethyl group of diethyl tartrate is replaced by an octyl group (Zoc. cit.), no indication could be found that the latter exerts any ‘‘ surrounding ” influence to prevent the easy introduction of two acyl groups. The second ethyl group has also been replaced by the octyl radicle, but even then there is no evidence of a, hindering influence exerted by the alkyl groups on the reactivity of the hydroxyl radicles of the tartaric molecule.In the preparation of the dioctyl tartrate, the same sec.-octyl alcohol was used as formerly. Dioctyl Tartmte. Ethyl octyl tartrate was prepared by the method already described and 35 grams of it were dissolved in 150 grams of octyl alcohol ; the solution was saturated in the cold with dry hydrogen chloride, and after standing at the ordinary temperature for three days the hydrogen chloride was extracted under reduced pressure and the residue distilled.1222 McCRAE : DI-SEC.-OCTYL TARTRATE AND The fraction distilling above 215' under 15 mm. pressure had a rotation of 4.15' in a 50 mm. tube a t 20'. This fraction was rectified and the oil which passed over at 215-225O under 19 mm. pressure showed a rotation of 4.05' in the same tube at 18.5'. The whole of the distillate which had passed over above 200' was washed with water, and after drying was dissolved in octyl alcohol ; the solution was then saturated with hydrogen chloride and treated as before.On dis- tilling the oil left after the extraction of the hydrogen chloride, a fraction was obtained which boiled at 225O under 20 mm. pressure and had a rotation of 3*60° i n the 50 mm. tube a t 18'. This rotation was not altered by redistillation of the ester, and the same rotation was obtained with different fractions of the same dictillation. Dioctyl tartrate is a viscous, slightly yellow oil with a rancid odour. The following density determinations were made : d 32'/4'= 1 *0077. d 45O/4'= 0.9967. The density a t 18O would be 1*0195; consequently [ a y - 3'6 =7*06', and [M]r =26*30'.- 0.5 x 1.0195 Dioctyl Dibennxoyltartmte. Preliminary experiments showed that by the action of benzoyl chloride on dioctyl tartrate a laevorotatory product was formed, and this, in analogy with the results which have been obtained for diethyl tartrate (Frankland and Wharton, Trans., 1896, 69, 1586), dibutyl tartrate (Freundler, Ann. Chim. Phys., 1894, [ vii 3, 3, 479), and ethyl octyl tartrate (Trans., 1901, 79, 1106), indicated that two acyl groups may easily be introduced into the molecule. It was evident, too, that the introduction of a single acyl group would be a matter of some diaculty, and consequently the original view was not realised. The dibeneoyl derivative was prepared by heating 40 grams of benzoyl chloride to 140° and slowly dropping in 9 grams of dioctyl tartrate with repeated shaking.The mixture was heated at the same temperature for two days until there was no further evolution of hydro- gen chloride. It was then poured into water and thoroughly shaken during two days with sodium carbonate solution. The oil was dissolved in ether, and the ethereal solution shaken with aqueous sodium car- bonate solution until the odour of acid chloride completely disappeared. The ethereal solution was washed, dried over ignited potassium car- bonate, then filtered, after which the ether was distilled off. A dark, oily residue was left which was dissolved in alcohol and shaken with charcoal. After filtering off the charcoal, the solution was quicklyDI-SEC.-OCTYL DIBENZOYLTARTRATE.1223 heated and water was added until there was just a permanent turbidity. On cooling, a slightly yellow oil was precipitated which, after drying, gave a rotation of - 22'50' in a 50 mm. tube. The oil was further purified by dissolving in alcohol and precipitating with water ; it was then dissolved in ether, dried over potassium carbonate, and the ether distilled off. The oil, which was yellowish and possessed a slightly rancid odour, was dried over sulphuric acid under reduced pressure, and gave a rotation of - 23'59' in a 50 mm. tube at 25'. Further treatment by the same method did not alter the rotation : 0*1320 gave 0,3390 GO, and 0.0856 H20. The following density determinations were made : C = 70.04 ; H = 7.20. C,,H,,O, requires C = 70.1 1 ; H = 7.90 per cent.d 2lo/4O= 1.0953. d 3Ot5O/4O = lq0860. CE 45'/4'== 1.0725. The density at 25O would therefore be 1,0913 ; eossequentIy [ a ] r = - 23'98 = -43.94', and [MITE -355.70. 0.5 x 1*0913 As the polarimeter used was not fitted with a heating arrangement, it was not possible to determine the influence of temperature on the rotation to find whether, in the case of the benzoyl compound, this passes through a maximum, as Frankland and Wharton (Trans,, 1896, 69, 1586) found to be the case with diethyl dibenzoyltartrate. Conclusions. The ester described above extends the series of tartaric esters, and for comparison the following table may be given : Dimethyl tartrate * ............ Dietbyl tartrate * ............... Di-n-propyl t,artrate * ......... Di-isopropyl tartrate * ......Di-rt-butyl tartrate t ......... Di-isobutyl tarfrate * ......... Di-sec.-oct yl tartrate ............ Ethyl sec.-octyl tartrate $ ...... [ u ] F = 1.83' [u]": = 7.66 [uK =12.44 [ u ] F =14*89 [ U]T = 10.3 [ ~]1,0~' = 19.87 [u]F = 7.06 [u]r = 7-78 [N]1,8"= 3.26' [MK = 15.18 [M]y= 27-37 [M]2,0" = 32 76 [My = 13-80 [M]bma= 26.62 [M]F = 26.30 [MJT = 22.55 The similarity of the specific rotations of diethyl and dioctyl tar, trates is striking, and may possibly be due to a rise of rotatory power t o a maximum, with subsequent rapid fall as the series of esters is ascended (see Frankland, Trans., 1899, 75, 547). The relationship * Pictet, Jahrmbcr., 1882, 856. t Freundler, A m . Chim. Phys., 1894, [vii], 3, 447. 3; McCrae, Trans., 1901, 79, 1106.1224 HARDEN AND YOUNG: GLYCOGEN FROM YEAST.between the rotations of diethyl and dioctyl tartrates is very similar to that between the rotations of ethyl glycerate and octyl glycerate, or t o that between the rotations of ethyl ncetylglycerate and octyl acetyl- glycerate quoted by Frankland (Zoc. cit., 354 and 355). Taking the view previously expressed, that substitution effected sufficiently far removed from the asymmetric carbon atom scarcely modifies the rotatory power, we may here find a confirmation of Guye’s proposition ,(Trans., 1901, 78, 476), inasmuch as substitution of a methglene hydrogen atom in the ethyl group of ethyl octyl tartrate by n-hexyl causes only a small increase in the molecular rotation, and the increase is only small even if we consider the replacement of a methyl- ene hydrogen atom of each of the ethyl groups of diethyl tartrate by cn-hexy 1. The comparatively high negative rotation of dioctyl dibenzoyl- tartrate shows that the introduction of two aromatic acyl groups into the tartaric molecule changes the dextrorotation into a lavorotation (Frankland and Wharton, Freundler, McUrae, Eoc. cit.), and it would therefore appew that this is quite general and is independent of the nature of the alkyl groups present. TEE YORKSHIEB COLLEGE, LEEDS.

ISSN:0368-1645    

DOI:10.1039/CT9028101221

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年代:1902

数据来源: RSC

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1224 HARDEN AND YOUNG: GLYCOGEN FROM YEAST. CXXV.-GZycogen from Yeast. By ARTHUR HARDEN and WILLIAM JOHN YOUNU. THE occurrence in the yeast cell of a substance which yields a reddish- brown coloration with iodine appears to have been first observed by Errera in 1882 (L'EpipZasnze dcs Ascomyc8te.s et Ze Glycogdne des vgqgttaux, Bruxelles, 1885, and Compt. Tend., 1885, 101, 253), although the existence of a carbohydrate reserve substance had been surmised by Pasteur in 1859. On account of this reaction, it was considered to be glycogen, and Errera attempted to extract it from the cell, but did not succeed in obtaining it sufficiently pure t o be certain of its identity with ordinary glycogen. It was next examined by Cremer (Munchener Med. Wochenschr., 1894, 41, 525), who stated that he prepared it from yeast and purified it by Briicke's method (precipitation of the proteids by potassium mercuri- iodide) and by fractional precipitation, 13 grams being obtained from 250 grams of dried yeast.He describes it as a neutral white powder, of specific rotation [ a ID + 198.9". It gave a red coloration with iodine, formed an opalescent solution in water, was converted by boiling withHARDEN AND YOUNG: GLYCOGEN FROM YEAST. 1225 dilute hydrochloric acid into dextrose, and was inverted by saliva, pancreatic juice, and diastase, A much more detailed investigation on this subject was made by Clautriau (Etude chirnique du Glycogdne. Mem. Coummgs, Acud. Roy. Belg., 1895, 53), who prepared glycogen from yeast, from two species of fungi, and from the rabbit, and carefully compared their properties.Clautriau made use of yeast which had been enriched in glycogen by treatment with wort containing 1 2 per cent. of cane-sugar, and after repeatedly boiling it with '1 per cent. aqueous potash and washing with water disintegrated the cells by making them into a solid mass with silica, chalk, and potassium silicate, and then grinding the whole to a fine powder. The glycogen was then extracted by boiling water, a,nd was freed from mucilaginous matters by the repeated production in its solution of a precipitate of calcium phosphate, the last traces of gum being removed by saturating the solution with salt and then adding ammonium sulphate in excess. The glycogen was precipitated from the diluted solution by an excess of iodine, the precipitate treated with sulphurous acid, and the glycogen precipitated by the addition of two volumes of alcohol, and finally washed with absolute alcohol and ether and dried in the air.He thus obtained it free from nitrogen, but containing 1-3-15 per cent. of ash, and observed that in its general properties it agreed with the substance described by Cremer. He found, moreover, that all the samples prepared by him, both from animal and vegetable sourcee, had the composition 6C,H,,O,,H,O, and were members of a group of closely allied substances, but were not identical in every respect. Extraction, and Pzcrij%ation of Yeast Glycogen.-Well washed and pressed yeast was mixed with an equal weight of fine, white sand and the cells broken by grinding for two hours in the disintegrator described by Rowland (J.Zhysiol., 1901, 27, 53), the mass being cooled during the operation by liquid carbon dioxide. The ground-up mass was then poured into two or three times its bulk of boiling water and boiled for about two hours. The liquid was separated in a centrifuge and the residue again boiled with water aud separated, the two extracts being then mixed. To the united solutions, 1 per cent. of sodium phosphate was added, together with an equivalent amount of calcium chloride, according t o Clautriau's method, and the whole mass, after having been neutralised with ammonia, mas heated on the water-bath, the calcium phosphate filtered off, the filtrate evaporated dowu, and the glycogen precipitated by the addition of an equal volume of alcohol. This operation was repeated as long as the glycogen appeared sticky and viscous on precipitation with alcohol, the calcium phosphate bringing down with it most of the mucilaginous material, The glycogen was then redissolved i n water, and the liquid1226 HARDEN AND YOUNG : GLYCOGEN FROM YEAST, first saturated with salt, then with ammonium sulphate, and allowed t o stand in a cool place for three days, By this means, the last traces of gum mere precipitated, the glycogen remaining in solution.After filtration, the liquid was freed from the greater part of the salt and ammonium sulphate by dialysis, and the glycogen precipitated by alcohol. To obtain the glycogen free from proteids, it was further found essential to treat it by the method described by Pfluger for the purifi- cation of animal glycogen (P’ilgsr’s Archiv, 1900,81, l), which consists in precipitating the glycogen from a solution containing 3 grams of potash and 10 grams of potassium iodide per 100 C.C.by the addition of half a volume of alcohol, filtering off, and washing first with a mixture of 300 C.C. of alcohol, with 400 C.C. of aqueous 3 per cent. potash containing 40 grams of potassium iodide, and then with 50 per cent. alcohol. After this treatment, the glycogen was freed from ash by being redissolved in water, and the solution precipitated with its own volume of alcohol in the presence of a trace of acetic acid, this opera- tion being repeated several times. Finally, it was again redissolved in water, precipitated with 1 volume of alcohol, filtered through silk, washed well with 50 per cent.alcohol, then with absolute alcohol, and finally with ether which had been carefully freed from acid, and was then allowed to dry in the air. The processes of solution in water and precipitation by alcohol must be repeated until the dried material is found to be free from ash. The purification was always carried on until 0*2-0°4 gram of the dried glycogen gave no ammonia by Kjeldahl’s process, and left no weighable amount of ash on ignition. The juice obtained by pressing out ground yeast with kieselguhr, according to Buchner’s method of obtaining zymase, may also serve as a source of glycogen, an equal volume of alcohol being added and the aqueous extract of the precipitate then treated as described above.Since the amount of glycogen contained in yeast varies very con- siderably with the condition and past history of the yeast, the yield of pure dry glycogen obtained also varies, but it may be taken to be on the average about 2 per cent. of the weight of the pressed yeast. For the purposes of comparison, samples of glycogen were prepared from rabbit’s liver and from oysters, Pfliiger’s method of extraction and purification being employed, and the purification carried to the same point as with the yeast glycogen; 570 grams of rabbit’s liver yielded 8.7 grams, and 1617 grams of oyster (1 gross) yielded 12 grams of pure dry glycogen. Cornpodtion.-Much diversity of opinion exists as to the com- position of glycogen both of animal and vegetable origin, AlthoughHARDEN AND YOUNG: GLYCOGEN FROM YEAST. 1237 Kekulh, in 1858 (Chern.Plmrm. CsntraZbZ., 3, 301), determined the empirical formula to be C,H1,O,, a number of investigators since that date, among whom may be mentioned Euppert (Zeit. physiol. Clmn., 1894, 18, 138), Chittenden (Annakn, 1875, 178, 266), Kiilz and Borntrager (PJuger’s Archiv, 1881, 24, 19, where a bibliography of the literature on this point is to be found), Vintschgau and Diet1 (Pjuger’s Archiv, 1878, 17, 163) and Clautriau (Zoc. cit.) have obtained figures agreeing with those required for the formula 6C,H,o0,,H,0, whilst Boehm and Hoffmann (Arch. exp. Path. Pharm , 1879, 10, 12) found numbers agreeing with those required for the formula 1 1 C6H,,05,H,0. On the other hand, Klincksieok, in 1861, in a single analysis of glycogen from the human liver (AnmaZen, 1861, 118, 229) and Bizio (Compt.rend., 1867, 65, 176), who employed glycogen from mollusca, obtained the formula C,H,,O,. Still more recently, Norking (PJEiiger’s Archiv, 1901, 85, 320) has obtained a similar result, using glycogen from horse flesh carefully freed from nitrogen and ash, and dried to constant weight a t looo. All these authors appear to have dried their glycogen at temperatures from 100-115° in an air-bath or a water-oven, with the exception of Bizio, who dried some samples at the ordinary temperature in a dry vacuum. Among these authors, Clautriau has paid special attention to the composition of glycogen extracted from yeast and fungi, and quotes a series of ten analyses referring to glycogen from four distinct sources (rabbit, yeast, Boletus, and Amanita).The glycogen in every case was dried at 105-110° in an oven until constant in weight, and the results, after allowing for the ash, agreed without exception with the formula 6C,Hlo0,,H,0, which requires C = 43.63 ; H = 6-26 per cent. I n two other analyses of glycogen from the rabbit, Clautriau ob- tained 44.1 and 44.0 per cent. of carbon, but in both these eases he found that the glycogen had become altered during drying, probably owing to the presence of small traces of acid, and yielded a solution in water which reduced Fehling’s solution freely. He attributes the high numbers obtained by some of the investigators already quoted to a similar cause. Our first analysis of oyster glycogen was made with material dried in the air at looo until constant in weight, and gave numbers even lower than those of Clautriau : 0.2092 gave 0.3308 CO, and 0.1247 H,O.It was found, however, that all the water could not be removed by C = 43.1 ; H = 6.6. 6C,H,,O,,H,O requires C = 43-63 ; H = 6-26 per cent.1228 HARDEN AND YOUNG: GLYCOGEN FROM YEAST. simply heating at looo in the air, and that a further quantity was lost when the glycogen was heated a t 100' in a vacuum over phosphoric oxide. The samples used for the following analyses were all heated in this way until constant in weight, the boat containing the glycogen being kept and weighed in a stoppered weighing tube and transferred t o the combustion tube as rapidly as possible. I n every case, a separate portion was dried in a similar manner, dissolved in water and tested for reducing'substances, but on no occasion could any reduction be observed. The two samples of yeast glycogen were separate preparations : I.Yeast glycogen : (a) 09249 gave 0.3639 CO, and 0.1283 H,O. C= 44-13 ; H = 6.34. (6) 0.1311 ,, 0.2132 CO, ,, 0.0743 H,O. C=44*35; H=6*30. 11. Oyster glycogen : ( a ) 0.1974 gave 0,3189 GO, and 0.1120 H,O. C544.06; H=6*30. ( b ) 0,1643 ,, 0,2669 CO, ,, 0.0924 H,O. C=44*30 ; H= 6-25. 111. Rabbit glycogen : (a) 0.2559 gave 0.4167 CO, and 0,1462 H,O. C = 44.41 ; H = 6.34. (6) 0.2611 ,, 0.4232 GO, ,, 0.1458 H,O. C=44*20 ; H=6*20. C6H,,0, requires C = 44-44 ; H = 6.17 per cent. 6C,HI,0,,H ,O requires C = 43-63 ; H = 6.26 per cent. These results all agree, within the limits of permissible experimental error, with those required for the formula C,H,,06, thus confirming the formula originally obtained by Kekul6 and a t the same time showing the identity in composition of the glycogen derived from yeast with that derived from animal soiirces.As none of the investigators who obtained low numbers for glycogen dried their material in a vacuum, it seems probable that their results were due to the presence of small quantities of water, the amounts of which would naturally vary with the humidity of the atmosphere in which the glycogen was heated. Speci$c Rotation.-The opalescence of aqueous solutions of glycogen renders the determination OF its specific rotation extremely difficult, and hence the results obtained by different observers differ somewhat widely, varying From + 213O to + 1 8 4 O .The results hitherto obtained f o r the glycogen of yeast are those of Cremer, [a],= 198.9", and of Clautriau, [a]= = + 184*5O, or, taking glycogen as C6HIOO5, [aID = 187.9". Using a Landolt-Lippich polarimeter, reading to O - O l O , with sodium light i t was only found possible t o employ solutions containing 0.1-0-2 gram per 100 C.C. Since glycogen which has been thoroughly driedHARDEN AND YOUNG: GLYCOGEN FROM YEAST. 1239 dissolves very slowly in water, it was found advisable to employ air- dried glycogen, the weight of the dried glycogen being found by drying a separate portion of the same sample in a vacuum over phosphoric oxide at 100' and allowing for the same percentage of water.Each of the following results was obtained as the mean of two independent sets of 15 readings made by two observers : I. Oyster glycogen : ~=0*1083; 2=1; u E = + 0.207O; [a]:"= +191*2O. 11. Rabbit glycogen : 111. Yeast glycogen : ~ = 0 . 1 2 0 4 ; Z=1; ar= + 0.23 ; [u]g"= 191.1 . ( a ) i. c=0*1730; Z=2; UY= 0.682; [u]Y= +197*1O. ii. c=0*1937; Z=2; UY= 0.790; [u]F= 203.5 . (b) i. c=0*1558; Z=2; uT= 0.616; [a]""= 197.7 . ii. c=0*1739; Z=2; ~1,7"= 0,678; [u]:"= 194.9. Two separate estimations of each of two different preparations of yeast glycogen were made, the mean of the four being [ u ] ~ ~ " + 198.3'. This result is slightly higher than that of Clautriau and agrees well with that of Cremer. The difference between the value for yeast glycogen and that obtained for animal glycogen, in view of the low concentration of the solutions employed, cannot be considered as indicating any essential difference between the properties of the two substances. OpaZesce~ce.-Clautriau states that the glycogen which he obtained from yeast produced a much less opalescent solution in water than the specimens which he prepared from fungi and the rabbit, and estimated the opalescence of the yeast glycogen solution at about one-fourth of that of the others.The opalescence diminished and gradually disappeared when the solution was preserved under sterile conditions for a few days. It must be remembered that Clautriau's glycogen contained 1-3.15 per cent. of ash, We have also found that a solution of yeast glycogen is less opalescent than solutions of animal glycogen, a 1 per cent.solution of glycogen from the oyster possessing roughly 2.5 times the opalescence of a similar solution of yeast glycogen. Rabbit glycogen was found to yield a slightly more opalescent solution than the oyster glycogen. A comparison of two eeparate preparations of yeast glycogen showed that one of them yielded a solution which was somewhat more opalescent than that of the other, but the difference did not exceed about 5 per cent. The opalescence showed no signs of diminution when the solutions were preserved under sterile conditions for a fortnight,1230 HARDEN AND YOUNG: GLYCOGEN FROM YEAST Reaction with Iodine,--The coloration produced with iodine has also been observed to vary for specimens of glycogen derived from different sources.Thus, Clautriau found that yeast glycogen gave a darker coloration than that from fungi and from the rabbit, and that the coloration produced by the yeast glycogen disappeared at a somewhat higher temperature than that of the others, whilst Weinland (Zeit. Biol., 1901, 41, 69) observed that the glycogen derived from certain parasitic worms gave a much weaker reaction with iodine than mammalian glycogen. The three varieties of glycogen examined by us differed in the intensity of their colorations with iodine. The t i n t produced by rabbit glycogen was slightly deeper than that given by the yeast glycogen, whilst both of these were much stronger than that produced by the oyster glycogen. On heating, the coloration of the oyster glycogen disappeared before that of the others.Comparing two samples of yeast glycogen from separate preparations, i t was found that the coloration produced with iodine was in one case 25 per cent. deeper than in the other, The reaction was in all cases carried out by adding 2 C.C. of a 1 per cent. solution of iodine in 1.5 par cent. potassium iodide solution to 10 C.C. of a 0.2 per cent. solution of the glycogen, as recommended by Clautriau. Acid Hydrolysis.-Many observers have noticed that glycogen does not yield the calculated amount of dextrose when i t is boiled with dilute acids, and in this respect it resembles starch (Sachsse, Chem. Centr., 1877, 8, 732). Kiilz and Borntrager (P’idgeq*’s Archiv, 1881, 24, 28), in a long series of experiments with glycogens of different origins, obtained very varying results, the weight oE sugar obtained varying from 95.34 to 117.6 per cent.of that of the glycogen employed, the calculated amount for their glycogen, 6C,H,00,,H,0, being 109-09 per cent. They also determined the rotations of the solutions obtained and found that these corresponded with the dextrose calculated from the copper reductions within about 1-4 per cent. Still more recently, Nerking (PJzXger’s Arohiu, 1901, 85, 320) has shown that glycogen derived from horse-flesh only yields 97 per cent, of the calculated amount of dextrose when 0.2-0*4 gram of the glycogen is boiled for 3-5 hours with 100 C.C. of 2.2 per cent. hydro- chloric acid. He also found, as the result of a number of separate experiments, that a longer or shorter period of action or a weaker acid all produced a lower result. Since no observations appear to have been made hitherto on the course of the hydrolysis of a single sample of glycogen, the behaviour of the three varieties of glycogen referred to above towards diluteHARDEN AND YOUNG: GLYCOGEN FROM YEAST.1231. acid was examined by heating them in 1 per cent. solution in semi- normal hydrochloric acid (1 *82 per cent. HCl) in a boiling water-bath, the course of the reaction being followed by removing samples at intervals, cooling rapidly to 1 5 O , observing the rotation in a 2 cm. tube, and then making up 10 C.C. of the liquid to 25 C.C. with 5 C.C. of normal potash and water, and estimating the reducing power of 20 C.C. of this solution with Fehling's solution by Brown, Morris, and Millar's method (Trans., 1897, 275).The experimental numbers were in every case plotted on squared paper against the time, a curve drawn through them, and the values taken from the curve. The results obtained show that in every case the rotation of the solution falls, a t first rapidly and then very slowly, whilst the cupric reducing power increases at first rapidly, and then slowly, until a maximum is reached -+ Time in hours. Sugar from cupric reduction. --... Botation in degrees. after which it slowly decreases, This is shown in the accompanying curves, in which the actual rotation and the dextrose calculated from the cupric reducing power are plotted against the time for a sample of yeast glycogen. In the following table, the numbers for each specimen of glycogen are given under two headings : (1) dextrose calculated from the cupric reducing power, and (2) dextrose calculated from the rotation, the latter being calculated on the assumption that the rotation of a 1 per cent.solution of dextrose at 15" in P 2 cm. tube is 1-05'. The average deviation from the smoothed curve of the numbers expressing the dextrose calculated from the cupric reducing power is only 0.7 per cent., and in only four observations does the deviation exceed 2 per cent. :1232 HARDEN AND YOUNG: GLYCOGEN FROM YEAST. Yeast glycogen. -. Rabbit glycogen. a. - Time in Hour: 1 2 3 4 5 6 7 8 9 10 11 12 13 1 4 15 16 - Oyster glycogen. 1'433 1.160 1.093 1'082 1.075 1.072 1.070 Dextrose calculated from - 0-700 0.940 1.035 1.058 1.065 1'068 Reduc- tion..I__ - 0.900 1.010 1'055 1.075 1 *08 4 1.088 1.086 1 -084 1 '083 1.081 1.078 1'069 - - - - - - Rota- tion. - 1 - i 1.055 I 1.052 I I - - 1.218 1.177 1 -1 43 1'122 1.098 1 -088 1.077 1.065 1-06 1.05 1'047 - -- - Reduc- tion. 0.916 1.013 1'051 1.070 1.078 1-082 1.085 1.083 1.081 1 '080 1-072 - - - - - Rota- 1, Reduc- tion. tion. Rota- tion. 3'24 2.20 1 :470 1-206 1.123 1'088 1'070 1.060 1 '055 1 -052 1'050 1.050 1 '048 1'047 - - Reduc- tion. 0.952 1 '032 1'065 1,080 1'089 1.090 1'092 1.090 1'088 1.087 1.082 - - - - - Rota- tion. 1.370 1.181 1.128 1'112 1.105 1 '1 02 1'101 1'100 1'100 1 '100 1 '099 - - - - - I n thecase of the rabbit glycogen, the maximum was obtained after 8 hours, and amounted to 96.3 per cent. of the calculated amount (the temperature in this case was slightly below 100' for the first hour).Of two separate samples of yeast glycogen, one yielded the maximum of 97.9 per cent. of the calculated in 7 hours, and the other a maximum of 97.6 per cent. also in 7 hours, Finally, the oyster glycogen produced a maximum of 98.3 per cent. of the calculated amount in 7 hours. It will be seen that when the maximum reducing power is attained, the rotation of the solution correspond# with an amount of dextrose almost exactly equal to that calculated from the reducing power. The differences observed are not greater than might be expected under the conditions of the experiment, a polarimeter reading of only O*0lo corresponding with a difference OF 1 per cent. in the dextrose. No special examination of the early stages of hydrolysis has as yet been made. From a consideration of the various properties of glycogen from yeast and from animal sources, it appears that no well marked difference exists betwesn these substances. All the three varieties examined by us have the same compositionROBERTSON: ATOMIC AND MOLECULAR HEATS OF FUSION. 1233 and the same optical activity. The differences observed between yeast glycogen and animal glycogen as regards opalescence, reaction with iodine, and behaviour towards dilute acids are not greater than those which exist between the two specimens obtained from the rabbit and the oyster. How far the degree of opalescence in solution and of coloration with iodine are characteristic of glycogen from a definite source is not a t present known, but the difference in this respect between the two samples of yeast glycogen examined by us and the divergence of our results in these particulars from those obtained by Clautriau seem t o indicate that these properties cannot be considered as essential. We are a t present engaged on the study of the early stages of acid hydrolysis of yeast glycogen and of the action on it of diastatic enzymes, and in particular of that of yeast itself. JENNER INSTITUTP OF PREVENTIVE MEDICINE.

ISSN:0368-1645    

DOI:10.1039/CT9028101224

出版商:RSC    

年代:1902

数据来源: RSC

摘要:

ROBERTSON: ATOMIC AND MOLECULAR HEATS OF FUSION. 1233 CXXV1.-A tornic and Molecular Heats of Fusion. By P. W. ROBERTSON. No satisfactory relationship has hitherto been found between the latent heat of fusion of substances and their atomic or molecular weights. Crompton (Trans., 1895, 67, 315) supposed the equation p/Tv= a constant to be true for the elements, where p is the atomic latent heat, T the melting point on the absolute scale, and 9 the valency. Apart from the fact that the experimental numbers give but poor agreement with the formula, exception must be taken to an expression which involves such a variable Later, Deem (Proc., 1895, 11, 125, and Chem. News, 1897,76, 234) concluded that p / T is a constant only in the case of certain groups of similar elements. In 1897, Crompton arrived at the result that dw/T= a constant for unimolecular liquids, w being the latent heat and d the specific gravity of the liquid (Trans,, 1897, 71, 925).Concordant values were ob- tained in the case of a number of organic compounds which had been proved unimolecular by other methods. When the results were too high to agree with the above expression, Crompton concluded that the liquids were proportionately associated. The number varied from 0.1 to 0.4 with the elements, the results being calculated in many cases from the specific gravity in the solid state. De Forcrand ( C m p t , red,, 1901, 132, 878) ahowed that the rela- VOL. LXXXI, 4 N constant ” as valency.1234 ROBERTSON: ATOMIC AND MOLECULAR HEATS OF FUSION. tionship M( W -I- w)/P is approximately constant, where iK is the mole- cular weight of the substance in the state of a gas at the boiling point T’, W the latent heat of vaporisation, and w the latent heat of fusion.Owing to the large magnitude of Was compared with w, in general, the results have little dependence on the latent heat of fusion. Further, BW/Z” = constant (Trouton’s law). By combining this with De Forcrand’s formula, it follows that V/w= a constant. Using the values obtained by Traube for the latent heats of vaporisation of the following elements,. which give concordant results for Trouton’s formula, the values of W/w are approximately : Bromine = 3 Iodine = 3 Zinc = 14 Cadmium = 15 Mercury = 25 Bismuth = 16 According to De Forcrand’s formula, these numbers should be identical.When the values of Aw/Tare considered, i t is seen that with few exceptions they have a certain periodic character. It would seem therefore that some periodic quantity must replace the value of the in Crompton’s formula to make it true for all the elements. It can be proved that TS/w =a constant, where X is the specific heat of the element, by using the relation TC=s constant, C being the coefficient of expansion. But Pictet proves that 2°C vy= a constant, the expression vv representing the mean distance between the atoms if Y is the atomic volume. Applying this, it follows that = a constant (Dulodg and Petit) FXG/T/W = a constant .*. Aw/TqT -5: a constant but AX It will be found that this expression agrees more accurately with the results of experiment than any which has hitherto been proposed.In Table I (p. 1235) are given the value8 of this expression for those elements with atomic weights above 40 the latent heats of which are known. Most of the const,ants required have been taken from Cromp- ton’s papers ; the values for copper and silver are due to Heycock and Neville, and the latent heats of lead and thallium have been deter- mined by the author, The value for lead is thus seen to be somewhat below the normal, whilst those of bromine, bismuth, and gallium are too high. It is a remarkable fact that the two latter elements expand on freezing, which occurrence is of comparative rarity, The specific volumes, except in the case of bromine, are those of the elements in the solid state. If the latent heat of bromine has been correctly determined, it wouldROBERTSON: ATOMIC AND MOLECULAR EEATS OF PUSION.1235 Element, ~ ~~ Zinc ............ Cadmium ...... Mercury ...... Palladium.,. ... Platinum ...... Gold.. .......... Tin.. ............. Lead ............ Thallium ...... Iodine ......... Copper ......... Silver.. .......... Bromine . . , , , , Bismuth ...... Gallium.. ....... - AW. 1839 153i 565 3873 5295 3227 1573 1340 1470 1485 3140 2920 1295 2602 1336 - - T. 688 593 234 1773 2052 1335 503 598 562 387 1355 1230 266 540 286 - 7 3 - Y. TABLE I. 2'10 2 *35 2.41 2'02 2'10 2.15 2.55 2 '61 2'57 2-95 1 '93 2.16 2'99 ' 2.77 2-28 - Robertson, pIT3JE 1 '28 1'10 1 '00 1 *08 1 '23 1-11 1 '23 0.87 1 '02 1 '29 1 '20 1'10 (1.63) 1-75 2'05 I'ercen tage deviation rom mean. + 13 - 3 - 11 - 4 $ 9 - 2 + 9 - 23 I- 10 + 14 + 6 - 3 - - - Clromptoii 1895, PI TV.1-31 1 2 9 1'21 1-09 1'29 0'80 1 *56 1'12 2'62 1-27' 1-16 2'37 1 '62" 1'60 1 *56 2rom p ton 1897, 10 x dw]T. 2-65 1 '84 1-65 2-83 2 -33 2 '36 1.86 1-22 1 -52 1.48 3'25 2'30 1.34 2-32 3 *98 * The valency of the halogens is taken as 3. seem probable that this element, like bismuth and gallium, expands on freezing. On comparing these results with those obtained by Crompton, i t is readily seen that the most definite relationship of this type yet obtained is as follows :--For the elements with atomic weights above 40 which do not expand on freexing, the atomic heat of fusion divided by the meltingpoint on, the absolute scale into the cabe Toot of the atomic volume is a constunt. Excluding bromine, the mean percentage deviation is k 10, with 1.13 as the mean value of the constant.It is interesting to note that in Dulong and Petit's law the variation from the mean is about +, 7 per cent. Since Dulong and Petit's law cannot be said to apply to compounds, it would seem improbable that the expression M w / T v v would yield constant results with the molecular heat of fusion. As a matter of fact, however, certain definite relationships are obtained in the case of compounds also. Thus the binary inorganic compounds and certain groups of organic compounds yield numbers in close agreement with one another. But the latent heats of those organic compounds which contain a large number of atoms in the molecule show wide deviations from the law ; for example, the latent heat of stearic acid (56 atoms) is about twice that calculated from the formula.This difference might be attributed (a) to the high molecular weight, (b) to the larger 4 ~ 21236 ROBERTSON: ATOMIC AND MOLECULAR HEATS OF FUSION. number of atoms in the molecule. That it is not due to the high molecular weight is shown by the fact that tribromoaniline and tribromophenol give latent heats in accordanc with the predicted values. The most probable explanation of the irregular results obtained with compounds containing a large number of atoms in the molecule would appear to be that J F does not truly represent the mean distance between the molecules. The possibility thus presents itself that accurate latent heat determinations may serve as a means for the calculation of this constant : TABLE ~I.-~%ovganic Compounds.Compound. Water ....................... Iodine chloride ............ Antimony chloride ...... Antimony bromide ...... Arsenic bromide ......... Tin tetrabromide ......... Lead chloride ............... Lead bromide ............ Lea.d iodide ............... Silver chloride ............ Potassium nitrate,. ....... Sodium nitrate ........... 1439 2297 3020 3490 2740 2910 5810 4520 1 5300 4400 494 9 5516 T. 273 289 346 367 295 303 758 763 648 730 606 579 37. 2.70 3'70 4-19 4 -42 4 -39 5-09 3 '64 3.80 4-17 3-07 3-65 3 -36 1 *96 2'14 2-09 2.15 2.11 1 '89 2.10 1 -56 1-98 1-96 2 *24 2 81 2.93 1'52 1 -03 1-10 * 1'08 * 0-73 * 1'60 * 1-23 * 1-10 * 2-31 * 1-69 * 2-46 * * Densities taken in tke solid state, Good agreement is shown amongst the binary compounds with the single exception of lead bromide.From electrical experiments, Weber has found the latent heat to be somewhat greater than that given in the table, whilst his value for latent heat of lead chloride was in close agreement with that found directly. Taking his value for lead bromide, the value of the expression Mw/F Jvbecomes 1-76, The mean variation for these ten compounds, with molecular weights ranging from 18 to 438, is only +, 5 per cent. from the mean. I t is remarkable that water agrees with the other compounds although it expands on freezing.ROBERTSON: ATOMIC AND MOLECULAR HEATS OF FUSION . 1237 TABLE III .- Organic Compounds . 2344 4906 4127 Compound . 298 4.36 383 4.41 321 5-36 Formic acid ............Acetic acid ................ Chloroacetic acid ....... Benzoic acid ............. Phenylacetic acid ....... Phenylpropionic acid . Lauric acid ................ Steazic acid ............. Naphthalene .............. Phenanthrene ........... Diphenyl ................. Di yhen ylmethane ........ p-Chloroaniline ........... p.Dichlorobenzene ....... p-Dibromobenzene ..... p-Bromophenol .......... Tri bromophenol ........ Tribromoaniline ........ Nitrobenzene .............. m-Dinitro benzene ........ Nitronaphthalene ........ o-Nitrophenol ........... Phenol ..................... Resorcinol .................. Thymol ..................... I- -_ 2640 2661 3890 4607 4293 3720 8985 13520 4559 4450 4391 4661 Acids . 266 277 334 396 350 322 316 337 Hydrocarbons .353 373 343 300 3 -33 3.84 3-91 4-56 4.80 5-14 6 *13 6.93 4-81 5-45 5 '36 5-54 Halogen derivatives . 4742 4395 4862 3961 4301 4608 342 325 358 33 7 366 395 2743 4901 4383 3725 Nitro.deriuatives . 264 363 329 316 Phenols . 4'13 4'90 5-04 4'62 4 -96 5.14 4'45 4-81 5'06 4.60 IlwlT 37 2.98 2.50 2 '98 2.61 2 '56 2.25 4'64 5'79 2 *67 2-19 2 '39 2'80 2-93 2 *76 2 *70 2.55 2-37 2.27 2-34 2'81 2'64 2'56 1'80 2 *90 2-40 10 x dwJT . 2-71 1'61 1-71 1.08 1'00 0 . 87 1-24 1'19 0.99 0*71 0'83 0'90 1'30 1-15 1'06 1-09 0'93 0'86 1'02 1'21 0.97 1-10 0'89 1'37 d-81 _r1238 ROBERTSON: ATONIC AND MOLECULAR BEATS OF FUSION. TABLE 111.-Organic Compounds (continued). 3830 4177 3720 Compound. 324 312 316 Diphen ylamine ........... a-Naphthy lamine ......... p-Toluidine ..............3022 3631 5187 4285 4070 3874 Acetophenone ............ Benzophenone 333 322 342 308 294 350 Acetoxime .................. Urethane .................. Azobenzene ............... Azoxybenzene ............ Anethole.. ................... Thiosinamine ............ 4.72 4 67 4-96 Aromatic Ketones. 4361 3588 i z Jliscellcbneous. 4 -86 5'40 4.22 4.30 5'31 5.42 6 '30 4.56 lFw/ T 3E ___-- 2-51 2-87 2 '38 2.52 2.51 2.15 2'62 2.85 2-57 2-61 2'43 LO x dwl II'. 0-78 1'21 0'95 1 *05 0'90 1-12 1 '34 0.87 0 '88 0'94 1'14 It is at once apparent that the agreement in the case of the organic substances is not as close as that observed amongst the inorganic binary compounds. There are, indeed, several striking exceptions. Thus phenol shows a deviation of more than 25 per cent. from the mean. Of the 36 organic substances mentioned, more than 30 give numbers which do not vary to a greater extent than f ' 7 per cent.from the mean. To test the theoretical considerations enumerated above, the latent heats of several substances of more or less importance to the result have been determined. I n addition, it has been necessary to find the specific gravities of a number of organic compounds in the solid state. In the determination of the latent heat, the simplest apparatus was employed. The substance placed in a test-tube was heated to the required temperature in a hot-air bath, and when the thermometer in the tube and the one in the bath registered the same temperature, the test-tube and its contents were rapidly plunged into a large calorimeter fjtted up with the usual precautions.This operation was repeated at Jiffereat temperatures, Lq the casg of the FpefalsJ the solid piece wa/sROBERTSON : ATOMIC AND MOLECULAR HEATS OF FUSION. 12% caught by the stirrer as it fell from the fractured test-tube. In repeating the experiment, a tube of equal weight was employed. The loss of heat of the calorimeter by radiation was practically nil when the latent heats of the metals mere being found, as the final temperature was reached in so short a time. Owing t o the paor cony ductivity of the organic compounds, however, the time taken to acquire the final temperature was considerably longer, although even in this case the change due to radiation is hardly noticeable. In general, when two observations were made a t the same temperature, one was made with the water in the calorimeter slightly below the temperature of the air and the other a little above.The solid organic compound was heated t o about 20' below its melting point, and several observations made a t about this temperature. It was found inadvisable to work at a higher temperature with the solid, for the presence of impurity is apt to make the specific heat increase rapidly near the melting point. Groups of observations were then made at intervals of 10 and 30Oabove the melting point. TABLE 1V.- Water + Water Value of Calorimeter = 630 grawts. Substance. Thallium.. ...................... ,, ........................ ,) ........................ ,, ........................ ,, ........................ ) ) ........................,, ........................ ,, ........................ ,, ........................ ........................ Lea); ......................... ,, ......................... ), ........................... ,, ......................... ,, .......................... ,) .......................... ,, ........................... Tin ............................. ,, .............................. ,, ............................. ,, ............................. ,) ............................. ,, ............................. ), ............................ ,, ............................. Phenanthrene .............. .............. 9 ) 3 , 9 ) .............. .............. Weight. 36 36 36 36 36 49 49 49 49 49 45 45 45 45 45 45 45 43 43 43 43 43 43 43 43 16 16 16 16 Temperature.230 230 255 315 350 240 260 265 305 330 260 260 290 290 350 350 365 160 160 190 190 240 270 285 290 75 80 85 110 Final tempera tnre. 18.05 17'15 22'05 3 8'1 18.5 17-4 18.6 18'25 19'45 20 '4 18-15 18.05 20.55 18.3 21'1 20 '6 19'6 16'35 19'95 19'1 19.9 22-0 19'95 19.8 22'2 21-45 24.0 24'4 21'45 Bise. 0.75 0.80 0.85 15 1.7 1.1 1'15 192 1 -9 2 '0 0 '9 0.95 1'05 1-05 1.8 1 '8 1-9 0.75 0'75 0'9 0'9 2'1 2.3 2 '35 2-4 0.55 0.5 0 55 1-551240 ROBERTSON: ATOMTC AND MOLECULAR HEATS OF FUSION. TABLE 1V.- Water + Watec Value of Calorimetev = 630 grams (continued). Substance. Phenanthrene . . . . . . . . . ....., Phenylacetic acid . . . . . . . . . . . , Y Y .............. .....*..... I 9 Y 7 ) Y Y Y Y Y Y .... ....... < .... * ...... . .... ....... 1 . . . . . . a * . . . I m-Dinitrobenzene , . . . , . . . . . . . 1 9 S Y Y Y Y Y 9 ) . , . . . . , . . . . . . . . . . . . . . . . .. .......... . . . . . . . . . . . . . . . . . . . . . a , . Thiosinamine . . . . . , , , . . . . . . . . . . 9 ) Y 9 ........... ....... ................ .. ,................. Y9 PY # Y ... ..,............ ........... I.. ... Tribromophenol.. . . . . . . . . . . . . . . . . . . . . . . I . . . . . 9Y Y Y Y Y Y Y 9 ) .... ..... ,..... *.............. ............... ............... Tribromoaniline.. . . . . . . . . . . , . . Y t Y Y I $ Y 9 Y 9 ............... . . . . . . . . . . . , . I . ....... .*...... . . . . . . . . . . . . . . . ....... *. .... * Weight. 16 16 25-3 25.3 25-3 25.3 25.3 25 -3 25.3 20 20 20 20 20 20 20 .a 20'2 20'2 20 *2 20.2 20'2 16 16 16 16 16 16 16 16 16 16 16 16 Temperature, 115 130 60 60 80 80 90 95 115 70 70 100 100 110 120 60 60 98 98 125 125 60 60 100 100 120 120 85 85 130 130 150 150 Final temperature. 19.7 21 -8 22-35 17.95 22.2 21 '8 23.05 20 *2 20-8 20-55 23 -5 20 -1 23.2 83 -1 21'0 20.2 19-55 18.3 23'25 20'95 22-35 19.6 20.6 19.55 21.1 22.2 21 -05 14'75 16% 18.36 18.45 17.95 16'5 Rise.1.7 2'0 0.5 0.55 2-1 2'2 2 '4 2.6 3.15 0 *5 0.5 1 -7 1.75 1.8 1.95 0% 0-65 2-35 2.25 2.75 2.8 0.35 0.35 1-05 1.05 1 '2 1 '3 0.65 0.65 1.5 1.6 1 *8 1-85 Latent Heats. (See Tab& IV.) Thalliuna.-The metal was heated in an atmosphere of coal-gas. Two series of experiments were performed, using different amounts of material. In the first series, the latent heat was found to be 7.0, and in the second, 7.4; mean, 7.2.The melting point was assumed to be 290'. This value for the latent heat is widely different from that (5.12) obtained indirectly by Heycock and Neville (Trans., 1894, 65, 31). Their value, however, is calculated from the atomic falls of only three metals. Further, the material they used contained "at least 98 per cent. of thallium." Small quantities of impurities are known to have a noticeable effect on the latent heat j thus, 3.5 perROBERTSON: ATOMIC AND MOLECULAR HEATS OF FUSION. 1241 cent. of solid matter has been found to depress the latent heat of ice from 80 to 54 (Petterson). The thallium used by the author was shown to be almost pure by the following analyses : 0.2292 gave 0.3710 TlI. 0.2348 ,, 0.4678 Tl,PtCl,.T1= 99.74 per cent. Lead.-From these experiments, the latent heat is found to be 6.45, assuming the melting point to be 330'. The results obtained by previous observers are : (1) Rudberg, 5.858 ; (2) Person, 5-369. The atomic falls obtained by Heycock and Neville in the case of lead vary so much that it is hardly safe to draw conclusions from them as to the latent heat of the metal. Taking the mean of the atomic falls between 4 and 6.4, the 1a.tent heat would seem to be about 6.3. The purity of the metal (Merck) used by the author is shown by the following analysis : T1= 99.81 per cent. 0.3224 gave 0.4728 PbSO,. P b = 100.15 per cent, Tin.-The experimental numbers give the value of the latent heat as 14-05, which is in close agreement with Person's value 11.262.The melting point was taken as 230'. Phenanthrene,-After separation from the anthracene present, which raises its melting point, the substance melted sharply at loo', and the melting point was not altered by recrystallisation. The latent heat was found to be 25. This is a little higher than the number 23, calculated from the molecular depression 120, obtained by Garelli and Ferratini (Gccxxettcc, 1893, 23, i, 442). PhenyZacetic Acid.-The acid used had a melting point of 77' and gave the latent heat as 32. Bruner" (Ber., 1894, 27, 2102) found the value 25.4 with a sample of the acid melting at 74.9'. m-Dinitro6el.lxene.-The latent heat of this compound does not seem to have been previously determined. A sample melting a t 90" gave the latent heat as 29.0. .Thiosinarnine,-This compound is doubly interesting from the fact that it is the only one in the list containing sulphur, and that it contains an ethylene linking. The material used had a melting point of 77" and gave the latent heat as 33.4.TribromophenoZ.-This substance is especially interesting on account of the magnitude of its molecular weight. The material used melted at 93' and was found to have a latent heat of 13.4. TribmoaniZine.-Two different preparations both melted at 122'. The latent heat obtained was 14.4. This is a little higher than that of tribromophenol. * Several of the latent heats obtained by this observer are lower than those of other experimenters, and some give smaller values for the expression Mw/T 37 than would be expected by analogy with similar compounds.1242 ROBERTSON: ATOMIC AND MOLECULAR HEATS OF FUSION.Substance. 1 Melting point. These Iatent heat determinations are summarised in the following table : Latent heat. -- I - Thallium .................................... Lead Tin ........................................ Phenanthrene .............................. Phenylacetio acid ........................ m-Dinitrobenzene ........................ Thiosinamine ............................. Tribromophenol ........................... Tribromoaniline ........................... ......................................... (290") (330) 77 90 77 93 122 (4;;) I I 7 -2 6'45 14.05 25 32 29.0 33.4 13-4 14-4 Specijic Gravities. It is a little remarkable that the specific gravities of comparatively few solid organic compounds are known, The values obtained in the following table were determined by means of the specific gravity bottle, water or petroleum of low boiling point being employed to fill the vacant spacc.The values given are the mean of two closely concordant results : Compound. Diphen ylamine ......................... m-Dinitrobenzene ....................... Benzophenono ............................. a-Naphthylamine ....................... Azoxybeiizene ............................. Thiosinamine ............................. Uretliane .................................. Chloroacetic acid ....................... Acetox in1 e ................................ Tribromophenol ......................... Tribromoeniline .......................... Sp. gr. 20"/20". 1.160 1.821 1.172 1'171 - 1*248 1.219 1 *11 1-53 0 -97 2.55 2.35 Molecular volume of solid. 105.6 111.1 155.3 122.1 158.8 95 -1 80.2 59% 75 -3 121.9 136.2 Slzcmmary. (1) For the elements with atomic weights over 40 which do not ex- pand on freezing, the expression Mw/r ,/p gives numbers the deviation of which from the mean is but slightly greater than that observed in the case of Dulong and Petit's law, (2) For the binary inorganic compounds, the mean percentage devia- tion of the values of Mw/TVTis only k5. (3) In the case of the carbon compounds, great regularityis noticedREVISlON OF THE ATOMIC WEIGIIT OF LANTBANUM. 1-29? among those of similar constitution, Thus for the disubxtituted benzenes the variation is 5 per cent. Compounds with two benzene nuclei give equally satisfactory results. There still remain a number of points to be cleared up in connec- tion with the subject of latent heats of fusion. Careful determinations with pure material of the latent heats of all the members of one or more series of organic compounds should throw much light on the relationship between lsteut heat, molecular weight, and chemical constitution, I n conclusion, the author would acknowledge his indebtedness to Professor Easterfield, who has superiatended the above work and helped him with much practical advice, VICTOI~IA UNIVERSITY COLLEGE, WELLINGTON, NEW ZXALAND.

ISSN:0368-1645    

DOI:10.1039/CT9028101233

出版商:RSC    

年代:1902

数据来源: RSC

摘要:

REVISlON OF THE ATOMIC WEIGIIT OF LANTBANUM. 1-29? CXXVI1.-Revision of the Atomic WeigAt of Lanthanum.* By BOHUSLAV BRAUNER, Ph.D., and FRANTI~EH PAVL~~EK,? Bohemian University, Prague. (Communicated by Professor Bohuslav Brauner.) THE atomic weight of lanthanum belongs to thom constants which have been relatively often determined, It is seen from Table I, given below, that since the year 1842, twenty-six series of determinations have been made by fifteen chemists, whereas in the case of, for example, the technically important iron, we possess only seven determinations. But whereas the numbers obtained for iron are all approximate to 56, those obtained for lanthanum differ considerably from one another, the minimum being La= 132.55 and the maximum La = 148.25 (difference = 15*7), and if we take into account only the most trust- worthy determinations made within recent times, we have a minimum of 135.0 and a maximum of 139.7, the difference being 4.7.In Table I, the first column contains the name of the chemist, and the numbers in brackets show that several determinations were made by the same chemist, The second column gives the date of publica- tion, the third coIumn indicates shortly the method used and the ratio from which the atomic weight mas calculated. The last column gives the resulting atomic numbers ” with regard to Q = 16. The numbers * The original paper, of which this is nn abbreviated version, was received ou t 8eaQ gavleetchek. February 24th, 1902.-[EDITOR.]1244 BRAUNER AND PBVLfeEK: REVISION OF THE were calculated from the data contained in the classical work of Clarke ( ' I A Recalculation of the A.tomic Weights." Revised Edition. Washington. 1897) . With regard to 0 = 16 and S = 32-07 used by Clarke. on using the international Ss32.06, which was used for the cal- culation of the results obtained in the g resent paper. the numbers of TABLE I.-Determinations of the Atomic Teiglht of Lanthanum . Chemist . Rammelsberg ....... Marignac (1) ....... Marignac (2) ....... Marignac (3) ....... Holzmann (1) ....... Holzmann (2) ....... Holzmann (3) ....... Czudnowicz ....... Hermann (1) ....... Hermann (2) ....... Hermann (3) ....... Zschiesche ........... Erk (1) .............. Erk (2) ............. Marignac (4) ........ CIeve (1) .............. Rrauner (1) ...........Brauner (2) ........... Cleve (2) .............. Bauer ................. Bettendorff ........... Gibbs and Shapleigl Schiitzenberger ..... Muthmann ........... Schiitzenberger ..... Atomic weight tables . Clarke ................. Clarke ................. Clarke ................. International ........ Richards .............. Date . 18 12 1849 1849 1849 1858 1858 1858 1860 1861 1861 1861 1868 1871 18fl 1873 1874 1882 1882 1884 1892 1895 1895 1899 1883 1893 1897 1897 1901. 1902 1902 1901 Method and raiio used . La. (SO.). : 3RaSO4 La.(SO.). : 3BnSO4 (A) La.(SO.). : 3RaS04 (B) La.(SO. ). : 3BaCI. Laz03 : 3BaSO. Lnz03 in La.(I0.)6.3H. 0 Ln.0. in La2Mg3( N03)12. 2413. 0 La. 0. : 3UaSO. LaCl. : Cl . ~ a ~ ( ~ 0 . j . : J.&o. Ln. 0. : 3CO. La.(SO.). : 1.a.O. La. (SO.).: La.0. LS. (so.). : 3BaS04 J..1.(S04). : La. O. La. O. : La.(SO.). La. O. : La.(SO.). La.0. : La2(S04)3 La.0. : La. La.0. : La.(XO.). La203 : h2(SO4)3 3C.O. and La.0. : La. (SO.). ,a.(SO.) ,. Principal fraction : : La.(S04). . P Side fraction : " Recalculation. " mean 3leve's and Brauner's numbers only American Commission Reports for 1900. 1901 ernian Chemical Society Commission Own table 1 La(0 = 16. S = 32.07). 132.55 139.53 148.25 141.27 139.46 '137.59 138.68 133.00 139.25 139.52 139.36 135-35 135.65 134.79 139.20 138.88 138 '36 138.36 138.V 138.71 139.71 138'0 135 138'4 2 13am 138'64 138'36 138.6 138 138.5 the table depending on the atomic weight of sulphur would be reduced by 0 002 . The last lines of the table contain the mean values. as calculated by different chemists.for their atomic weight tables . The abnormally low number. La = 135. which appears several times in the table is not without some historical interest .ATOMIC WEIGHT OF LANTHANUM. 1245 In 1870, Mendeleeff was of opinion that the quadrupled equivalent of lanthanum, 135 x 4= 180, represented its true atomic weight, and that the element belonged t o the fourth group. The determination of the specific heat of metallic lanthanum by Hillebrand, in 1874, proved that the order of the atomic weight of lanthanum is 138, but in spite of this Winkler, in 1891 (Bey., 24, SSS), considered that the composition of lanthanum hydride prepared by him is best represented by the simple formula LaH,, if we assume LaIV = 180. 1 have shown (Ber., 1891, 24, 1328) that the atomic weight of lanthanum cannot differ much from LalIT = 138.2, and that the hydride has the formula La2H3, which is analogous t o that of the hydride of the quadrivalent cerium, Ce,H,.On examination of the spark spec- trum of the fractions of lanthanum material yielding the apparent atomic numbers 132 to 135, I found that these low numbers are due to the admixture of yttrium (Y = 89). In 1898, on examining the solubilities of the oxalates of some rare earths in normal sulphuric acid, I found that t h a t of yttrium approaches that of lanthanum, so that on fractionating with oxalic acid certain lanthanum fractions may contain a n admixture of y t triurn. Although it was thus proved by me that the low numbers of about 135, obtained for the atomic weight of lanthanum, are due to an ad- mixture of yttrium, this abnormal value reappeared once more in chemical literature. Schutzenberger, in 1895 (Compt.rend., 120,1143), found that some fractions of lanthanum contained the ordinary lan- thanum, La=138, others a second lanthanum with the atomic weight La = 135. This lower number is regarded by Rydberg (Zeit. anorg. Chm., 1897, 14, 99) as the real atomic weight of lanthanum, as, according to his view, it agrees better with certain numerical relations observed by him in atomic numbers. 3 The objects of the present work were : (I) To ascertain whether the purest lanthanum preparations, that is, those corresponding with the most basic of all cerite earths, are homo- geneous, and what is the real atomic weight of the element contained in them.(2) To determine whether the atomic weight of lanthsnum is some- what higher than 138.4, for, according to the '' twin rule" of Loren2 (Zeit. anorg. Chem., 1895, 12, 329), it ought to approach the number La = 139. In this connection, it may be pointed out that if the number 618 = 139.0, calculated from the determinafiona of Wyrouboff and1246 BRAUKER AND ~tivr,rc~R: REVISION OF THE Verneuil (Bull. Xoc. Chirn., 1897, [iii], 17, 679) by Clarke (Annudl Beport of the Committee of Atomic Weights, 1897), for the atomic weight of cerium, be correct, we should expect the atomic weight of lanthanum to be considerably lower than Ln = 139. (3) To investigate once again the question whether or no, in ordinary lanthanum free from yttrium, fractions are contained the element of which possesses an atomic weight of 135, ( 4 ) To discover whether the classical method used for the determin- ation of the atomic weights of almost all rare earth elements, that is, the conversion of the oxide into the sulphste, contains any hidden source of error.Preparation of Mate~icd. In 1873 (Annalen, 168, 45), a new method was described by Men- deldeff for the easy separation of lanthanum from didymium. It con- sists in recrystallising the double nitrates with ammonium nitrate from an aqueous solution, This method was modified by Auer von Welsbach, in 1885 (Monatsh., 6, 491), who did not quote MendelBeff, and is therefore wrongly re- garded as the originator of the method, by recrystallising the double nitrates in the presence of nitric acid, At the end of his paper, in which the separation of the old didymium into “neodym” and “ praseodym ” (the latter separates with lanthanum) is described, this author says that lanthanum, like his ‘( twin ” didymium, will sooner or later disappear from the series of elements, a statement which means that, in his opinion, it consists of a mixture of elements. This fact was observed by me previously, in 1882 (Monatsh., 3, 176).A most negative ” fraction was obtained from lanthanum with an ‘‘ atomic weight ’’ of RIII = 140.19, and in the spark spectrum, in which the yttrium h i e s were prominent, some lines belonging neither t o lanthanum nor t o yttrium were observed. Mendeldeff’s method, as modified by Auer, was employed for the purification of the lanthanum material used by Bettendorff in 1892, as well as by Gibbs and Shapleigh in 1893 in their atomic weight deter- minations (see Table I), Quite recently, Melikoff and Pissarjewsky (Zed.mo?*g. Chem., 1899, 21, 70), without knowing that they return t o Mendelheff’s original method, recommend recrystallisation from the neutral solution for the preparation of pure lanthanum compounds. Many years ago, fractional precipitation with magnesia was recom- mended for the above purpose by Xtolba. Drosabach (Ber., 1896, m, 2452) used it for the separation of the yttrium earths. Without quoting their predecessors, Muthmann and Rolig (BeT., 1898,31, 1718) recommend i t for the euey and rapid preparation of p 9 * e lanthanum compounds, and they obtain from 470 grams oE the crude oxide mix-ATOMIC WEIGHT OF LANTHANUMI, 1247 ture 200 grams of perfectly pure lanthanum oxide.However, in a paper by Ley (Zeit. physikal. Chem., 1899, 30, 236), we find in a footnote the surprising statement that Muthmann and Rolig's material was in reality far from being pure, and contained yttria earths. Its original atomic weight was RII1= 139.5 and after fractionation a less basic portion with an atomic weight of R'" = 140.1 and a more basic portion with an atomic weight La = 138.4 are said to have been obtained. The material which was used for the preparation of lanthanum compounds for the purpose of the present investigation was obtained from cerite. Since the year 1885, much time has been devoted by me and by some of my advanced students to the fractional crystallisa- tion of a considerable quantity of the double ammonium nitrates of n crude mixture of lanthanum and old didymium free from cerium by the Mendelheff -Auer method.After a long series of crystallisations, lanthanum was obtained free from praseodym, neodym, and the whole of the elements of the samarium, gadolinium, and yttrium group. For the further purification, a second method was used consisting in the fractional fusion of the lanthanum nitrate thus obtained with a mixture of potassium and sodium nitrates in molecular proportion (Debray-Schutzenberger method). A trace of cerium and of the less basic earths was removed first by fusing for half a day a t 350'; the mass was dissolved in water, filtered, and the residue washed with a saturated solution of the alkali nitrates in water in order to avoid the finely divided oxides passing into the filtrate.The filtrate from this fraction, Al, was carefully evaporated down and the moist residue obtained had to be dried very carefully before fusion, a tedious operation requiring a great deal of time. On repeating the fusion, dtc., first at 450-500° and for the last fractions even at a higher temperature, the fractions A2, 8 3 , 8 4 , A5, and A6 were obtained. They consisted of basic lanthanum nitrate and were perfectly white. A third method of fractionation was used for the further purification of the highly puri6ed lanthanum material, A6, which did not contain the slightest trace of an yttria earth or of an earth yielding an absorption spectrum.Instead of using such weak bases as ammonia or magnesia, or of following Drossbach, who used sodium hydroxide, we used the most powerful base available, namely, potassium hydroxide, which precipitates lanthanum as the hydroxide. The latter, on being digested with a hot solution of, for example, lanthanum nitrate, is converted into the basic nitrate, and in such a precipitate the Zemt basic portion contained in the solution is accumulated, whereas the most basic or positive portion passes into the solution. I n this way, lanthanum solutions are precipitated by lanthanum hydroxide,1248 BRAUNER AND PAVLf6EK: REVISION OF THE The method of fractionation differed in one essential point from similar methods hitherto used, for instead of precipitating s w l l fractions and leaving the greater part in solution, the Zarger part was precipitated, leaving only the smaller part in solution, this considered to be the fraction sought.After calculating from a preliminary experiment the volume of a definite dilute solution of potassium hydroxide necessary for the complete precipitation of lanthanum, sufficient was added to the main solution to precipitate seven-eighths and to leave one-eighth in soh- tion. The addition was made drop by drop from a large burette and the precipitate digested for some time with the solution and then filtered. After dissolving the precipitate in the smallest amount of dilute nitric acid, and repeating the above process of fractionation, the following eight fractions were obtained : Lao, Lal, La2, La3, La4, La5, La6, La7.If lanthana is a mixture of earths, the lower fractions must contain the most basic (positive) portion, whereas the least basic (negative) portion will be accumulated in the highest fraction. The solutions containing the above fractions were first completely precipitated by potash, the washed precipitate was dissolved in an insufficient quantity of dilute nitric acid, which was added drop by drop with stirring, and the solution filtered from a small, insoluble residue consisting chiefly of silica and other negative impurities. After this, recourse was had to repeated precipitation with ammonia and washing of the precipitate in order to remove the alkalis com- pletely. From the nitric acid solution of the last precipitate, lanthanum oxalate was in each case precipitated by adding a dilute solution of sublimed oxalic acid drop by drop.The crystalline, white, and fine powder of the precipitate was well washed with water, but as the mode of washing has a great influence on the composition of the oxalate, this point will be more fully treated in a subsequent section (p. 1265). Method of the Atomic Weight Determination. It has been generally considered that the most simple and trustworthy method for the determination of the atomic weight of the element of a rare earth is the conversion of the oxide R,03 into the sulphate Bunsen dissolved the oxide in dilute sulphuric acid and removed the excess by evaporation, but as the reaction is an exothermic one, and the sulphates are only slightly soluble at a low, and still less 80 at a higher, temperature, some solid sulphate may separate out before the oxide has dissolved oompletely. R,(SO4)3.ATOMIC WEIGHT OF LANTHANUM.12 49 In order to avoid the error due to incomplete solution in sulphuric acid, the oxide is now generally dissolved in nitric acid, after which dilute sulphuric acid is added and the excess of the acids removed by evaporation. I n chemical literature, very vague and incomplete indications are found regarding the temperature at which the excess of sulphuric acid is removed from the sulphate. Although sulphuric acid boils a t 338’, a much higher temperature than this is recommended for its removal, and the sulphate is generally heated for some time at, or a little above, 400’ in order to remove all free sulphuric acid.The only chemist who has directed his attention to the question of the equilibrium between the basic and acid constituents of the sulphate of a rare earth is Bailey (Trans., 1887, 51, 683). On heating “didy- mium ” sulphate containing an excess of sulphuric acid slowly to and above 360’ he could not find any range of temperature within which the weight of the salt would remain perfectly constant. Each increase in temperature led to a further loss of weight and an equilibrium could not be obtained. Bailey says that it remains t o be seen whether the other earths of t h i s group show similsr variations. It should be added that a means of ascertaining whether the sulphate obtained by synthesis is normal was proposed by Cleve, Nilson, and others: it must dissolve in water without leaving an insoluble residue of the basic sulphate.This test only shows whether too much sulphuric acid has been removed, and yet we shall see that this criterion is not trustworthy. No one, however, has considered the other side of the question : How can we find out whether the sulphate does not contain an excess of sulphuric acid ? In the experiments recorded in this paper, we proceeded as follows. Air-dried lanthanum oxalate was heated gradually and carefully until the oxide was obtained. This mas heated in a double platinum crucible * to the highest yellow heat in a strongly oxidising flame. The oxide obtained from the fractions Lao, Lal, La2, La3, and La4 was at first perfectly white, but on being heated for a longer time the part in contact with the hot walls of the platinum crucible * The proposal to heat the platinum crucible (with the substance) which is to be weighed inside another platinum crucible was made by my former teacher, Prof. Stolba, some thirty years ago.The inner crucible does not come into contact with the flame gases, and d3es not change its weight. I t s surface does not become rough by crystallisation, or from little sand and dust particles which, being projected on the soft, white-hot metal, stick to it and make it often heavier. I have used the same crucibles for the last twenty year#, and they locjk like new to-day, and, what is more important, they do not leak, whereas crucibles which are heated directly over the blast invariably do so after a few months’ use, so that they become unfit for any kind of exact work, VOL.LXXXI, 4 01250 BRAUXER AND PAVL~CEK: REVISION OF THE assumed an extremely slight pale buff tint. This tint was slightly more prominent in the higher fractions, especially in La7. Lanthanum oxide, which was weighed after cooling over phosphoric oxide, was slowly and carefully dissolved in water to which nitric acid was added very gradually, after which a small excess of dilute sulphuric acid of known strength was added. A blank experiment made with the quantities used (5-10 C.C. of water, 2 C.C. of nitric acid, and 3 C.C. of sulphuric acid) showed that the residue obtained on evaporation in the air and after heating at 500° is inappreciably small, After evaporation to dryness, the platinum crucible was fastened in the centre of a large porcelain crucible having in its lid a thermometer graduated up to 550" by which at least the order of the temperatnre was indicated.The large crucibIe fitted into a larger plate of asbestos cardboard in order to exclude the products of the combustion of coal gas (chiefly water and carbon dioxide) from the atmosphere of the crucible. Experiment 1.-0.97175 gram La,OS was converted as above into the sulphate and the latter containing an excess of sulphuric acid was heated in the crucible air-bath. Time of heating. 3 hours 5 2 ) 5 Y ¶ 6 , I 5 ,, (total 24 hours) 3 9 9 6 9 9 6 3 9 4 ,, (total 19 hours) Direct flame in hand below red heat Temperature. 350"f 450"C_ I Weight of sulphate in grams. 1.711 2 1'7025 1'6990 1 *6982 1'6982 constant 1.6978 1.6955 1 '6949 r 1.6938 constant ;' Atomic weight 'I of La.133.70 133.52 136'28 136'48 136'48 136-56 137.06 137'20 137-45 137'41 137.62 It is seen from this experiment how slowly and incompletely the excess of sulphuric acid is driven off, and it will be seen later on that it cannot be driven off completely unless the substance be heated 200--300' above the boiling point of the acid. This behaviour is undoubtedly due to the presence of an acid sulphate of lanthanum analogous to the acid sulphate of cerium described by Wyrouboff (BUZZ. SOC. CILim., lS90, [iii], 2, 275). The vapour pressure of sulphuric acid in this salt must be smaller thanATOMIC WEIGHT OF LANTHANUM. 1251 that of the free sulphuric acid. The partial formation of this salt was-confirmed by our experiments." Lanthanum sulphate, obtained in Experiment I, was dissolved in water and the solution was found to be strongly mid towards ethyl- orange, But first the question had to be considered whether and bow far normal lanthanum sulphate is hydrolysed in aqueous solution, Ley (Zeit.plqsikal. Chem., 1899,30,236) found by physical methods that salts of lanthanum with strong acids are only very slightly hydrolysed,at the ordinary temperature, so that, for example, lanthanum chloride in aqueous solution shows, in the presence of phenolphthaIein, a very slightly acid reaction, but he says nothing about the sulphate. Behaviour of Lanthanum Subhate towayds Ethyl-orange. A larger portion of lanthanum oxide from the fraction A5 + 6 was converted into the sulphate with all due precautions, and this was heated for a long time to incipient redness in order to remove the excess of sulphuric acid as far as possible.It was dissolved in 6 parts of ice-cold water. One part of this solution was heated t o 35-40'; the hydrated salt which separated out was collected on a perforated platinum plate with the aid of a pump and well washed with water. From another part of the solution, the salt was precipitated with alcohol, collected at the pump, and well washed. The salt prepared by either method was heated in the crucible air-bath for a long time a t about 550°, and 1 gram of the anhydrous substance dissolved in 50 grams of water. On addition of 5 drops of B dilute (1 : 500) alcoholic solution of o w ethyl-orange, which was found to be more sensitive as regards the transition near the neutral point than o w methyl-orange, the above standccrd solution of lanthanum sulphate mas found to be very nearly neutral; it exhibited, however, a slight but distinct orange tint as compared with the same quantity of water containing the same quantity (5 drops) of ethyl-orange which was more yellow, so that it would seem that it is very sZightZy hydrolysed in aqueous solution.In all atomic weight determinations recorded below, the lanthanum sulphate was dissolved in 50 parts of water, and after addition of 5 drops of our ethyl-orange these solutions were titrated with N/20 to * In order t o avoid the mere assumption of the existence of a hypothetical acid snlphate of lanthanum, I asked Mr.Picek to prepare it, He succeeded in doing so by a novel method, differing from that used by Wyrouboff. The result of this work was the preparation of a whole series of acid sulphates in R pure state possessing the general formula R1112(S0,),,3H,S0, in which RII1=Ce, La, Pr, Nd, Y, and Sm. This fact was communicated to the Chemical Society on February 24, 1902. As the acid sulphates of Pr and Nd were described several weeks later by Matignon (CompQ. rend., 1902, 134, 657), I am obliged to make this statement in order to prove that our discovery was niaclo independently of that of Matignon. 4 0 21252 BRAUNER AND PAVLfeEK: REVISION OF THE N/30 solution of sodium hydroxide (sometimes a N/20 solution of sulphuric acid was also used, and the titration was done to and fro) until the above ‘‘standard” t i n t was reached.The volume of the alkali used was reduced to the corresponding volume of the N / l O solution and every C.C. multiplied by 0,0049038. The weight of sulphuric acid obtained is then subtracted from that of the weight of the ‘‘ crude ” sulphate. As it was found in several preliminary experiments, not recorded here, tbat the synthetical lanthanum sulphate, which was heated at about 500°, was rather strongly acid so that the correction determined acidimetrically would be rather large, we tried to diminish it by heaf- ing the salt at about 550° in an atmosphere of ammonia. For this purpose, ammocium carbonate was projected upon the red-hot bottom of the porcelain crucible containing in its centre the open platinum crucible, after which the lid of the porcelain crucible was replaced im- mediately.After several repetitions of this process, the sulphate obtained was far less acid, and even sometimes neutruZ or ~ormol, as regards the aqueous solution finally obtained. Lanthanum sulphate, obtained by evaporation of its nitric acid solu- tion, forms a loose mass of fine needles. On heating the salt to a temperature which in some cases may have finally exceeded 600°, that part which adheres to the platinum walls of the crucible may be5ome partly converted into the basic salt, that part which lies nearer the centre may consist of the normuE salt, and the uppermost inner layer may consist of some incompletely decomposed acid sulphate. On dis- solving such a mixture in water tinted with ethyl-orange, the salt at first rapidly dissolves with an acid reaction, then the solution proceeds more slowly, the acid reaction diminishes, and the last insoluble portion containing the basic salt is brought into solution slowly but completely by the free sulphuric acid resulting from the hydrolysis of the acid sulphate.It is a matter of mere chance that in some experi- ments the aqueous solution of the sulphate resulting after the above equilibrium had taken place was neutral. In other cases, it was acid. Innone of the 27 experiments recorded i.n this paper was the solid lanthanum sulphate piwpared by syltthsis homogeneously neutral or homo- geneous in all its parts. This is due to the circumstance that it hitherto has been found impossible to heat the system: crucible+ sulphate, throughout exactly to the Sume temperatwe.If it takes place according to an equation such as this, 3[La20,,2S0,] + La,O3,3S0,,3H2SO, + Aq = 4[La,03,3S0,] + 3H,O + Aq, it is seen that some water is set free, but no account can be taken of its quantity in the final calculation of the atomic weight. However small this The above process may be called one of c‘ self neutralisation.”ATOMIC WEIGHT OF LANTHANUM. 1253 unknown factor may be, it tends to make the atomic weight lower than the true number. It is seen from the above that the criterion proposed by Cleve and others for the test of normality of the sulphate obtained by synthesis does not hold good, for we are not entitled to reject the results of those experiments in which the sulphate does not dissolve in water at once but only after some time.Fimt 8 e ~ e s of Determinations. The following Table I1 contains the results of the preliminary series of syntheses of lanthanum sulphate. The oxide, as well as the sulphate, was weighed after standing for half-an-hour over phosphoric oxide. The weights were carefully corrected, the method of weighing was that by vibrations, the weights are given in air. The standards used are O= 16 and S= 32-06. ! h B L E I1.-8yntheses of Lanthanum Xukhate. (Preliminary). Pirst Series No. of experi- ment. 2 3 4 5 6 7 8 9 10 11 12 13 1 4 No. of fraction La 1 La 1 La 1 La 2 La 2 La 3 La 4 La 5 L a 6 La 6 La 7 La 7 A5+6 - La& gram (in air). 0.93205 0.8416 0.85993 0'7847 0 '80645 1.0760 1 .Of383 0.8721 0'9755 0'9188 0'9507 0.9677 0.8570 Sulpha t c '' crude ' grams.1'6198 1'46366 1'49518 1 '3635 1,40145 1'8707 1'51479 1'5160 1 '6948 1.5955 1'65212 1'68194 1,4880 Correction gram. nil - 0.00132 - 0.00078 nil nil - 0'00157 nil - 0.00151 - 0'00099 nil - 0'00172 - 0.00132 - 0'00064 - so3 corrected gram. 0.68775 0'62074 0.63447 0.5788 0.5950 0 -793 13 0'7873 0.64239 0 '71831 0.6767 0.6997 0'71292 0'63036 La203 per cent. in the sulphate. 57.541 57.552 57'543 57'550 57'544 57-567 57.572 57.584 57.592 57.587 67.604 57.580 57.619 Atomic weight La. 138-75 138 *82 138'77 138.81 138.77 138'92 138.96 139.03 139 -09 139.05 139'17 139'01 139'27 In passing in review the atomic numbers obtained from the different fractions of lanthanum, they are seen to rise slowly from 138.78, cor- responding with the most basic fraction Lal, to 139.08 corresponding with the least basic fraction La?, after which follows the less pure frac- tion A5 + 6, with a still higher atomic number 139.27.From this we might be entitled to conclude that the purest lanthanum material, which we have decomposed into eight different fractions, is not homo- geneous. The difference between the highest and lowest number,1254 BRAUNER AND PAVLfcEK: REVISION OF THE 139.08 - 138.78 = 0-3, is not very considerable, but it must be said here that after resuming the work with increased refinements, two new sources of error were diacovered which were removed by using a special arrangement for weighing. New Fractionation. In order to answer the question as to the homogeneity of our lanthanum, new methods were used for its fractionation : A.The purest lanthanum ammonium nitrate was purified by a series OF recrystallisations and the atomic number was determined. Experiment 15.-0#8262 gram La,O, yielded 1.4353 gram of the u neutral " sulphate, SO, = 0,6091 gram, La,O, = 57,563 per cent., whence La=138*89. This number corresponds to the mean of the above series : B. The second method of fractionation consisted in digesting lanthanum oxide with a concentrated solution of ammonium nitrate at about 80'. The more basic portion of lanthanum may be expected to pass into solution, and the less basic portion to remain un- dissolved. We made use of the circumstance that the limit of this reversible reaction (which follows the law of mass action) is displaced in one direction as the temperature rises, whereas it is displaced in the contrary direction as the temperature falls.After repeating this process with the soluble portion (the reaction is reversed when ammonia is added) and with the insoluble portion very many times, the most basic fraction Laa, and the least basic fraction Lap were obtained. After purification from silica, &c., in the manner indicated above (see page 1248), the hydroxide, oxalate, and oxide were prepared in turn, and the oxide was used for the atomic weight air are given) : No. of experi- ment. 16 l7 { l9 { 18 No. of fraction. Laa most positive LnS most negative - Sulphste ' crude " gram. 1 *66231 0.79589 2.34635 2,03961 - Correction gram. - 0~00098 - 0'00015 - 0'00561 - 0'00157 determination (weights irt - so, corrected gram.0.70481 0.33785 0.99320 0.86524 Per cent. La&), in the sulphate. 57 '576 57,538 57'569 57.545 - Atomic weight La. 138.98 138'73 138.93 138'79 These results are opposed to those previously found. Lanthana separated from other cerite earths could not be split up into different fractions possessing a diff erent atomic weight.ATOMIC WEIGHT OF LANTHANUM. 1255 The above was the state of the experimental work when Mr. PavliEek, in July, 1900, was obliged to leave the laboratory. With the intention of solving the question as to the real atomic weight of lanthanum with all possible accuracy, I undertook a further series of experiments which form a revision of the first part of this paper. Second Series of Determinatiom.It had now become obvious that the I‘ sulphate method ” of deter- mining atomic weights is full of hidden small sources of error which were almost entirely overlooked by the earlier workers in the large series of determinations quoted in Table I, and were discovered and avoided in this work only by degrees and not without difficulty and the sacrifice of much time. It must be remarked that the chemical method used in this part of the work was essentially the same as that described in the former part of this paper. The essential difference consisted in the manner in which the errors due to the hygroscopic nature of the material were avoided. The anhydrous sulphates of the rare earths are so extremely hygro- scopic that it is impossible to weigh them in a YeaZZy anhydrow state by using ordinary desiccators containing phosphoric oxide (Nilson) or to weigh them in closed weighing vessels made of light glass (Bunsen), as was done in tho first part of this work.It was necessary to avoid the absorption of any trace of moisture during the process of cooling and weighing, and this mas achieved by enclosing the crucible con- taining the still hot sulphate in a vessel containing completely dry air SO that it could not come into contact with moist air until the weighing was finished. I: succeeded in doing this by constructing a desiccator shown in the figures, 1, 2, and 3 (p. 1256). On the bottom of the desiccator (b, Fig. l), a thick layer of phos- phoric oxide is placed, and in i t stands a tripod made of thick copper wire.Into this tripod is placed loosely a light weighing glass provided with a perfectly ground conical stopper. The cover of the desiccator ( a ) has in its centre a neck closed by a perforated rubber stopper (c) carrying a small drying-tube filled with anhydrous calcium chloride and provided with two stopcocks ( d ) and (dJ. At a distance half way between the centre and the edge of the upper part of the cover (a), a round hole of about 8 mm. diameter is bored, and in this is fastened by means of rubber-solution a piece of thick-walled rubber tube (6) through which a glass fork (f) may be pushed and moved in both directions in a layer of I ‘ unguentum simplex.” This fork serves to open, raise, and close the stopper of the weighing glass while the desiccator remains closed, The fork (Fig.3) possesses two horizontal1256 BRAUKER AND PAVL&K: REVISION OF THE transverse furrows (9 9,) into which the handle of the glass stopper exactly fits. By pushing the fork downwards so that its teeth pass the handle of the stopper, and then turning the cover of the desiccator through 90°, the handle of the stopper falls into the furrows and rests upon them. The stopper is then easily raised and its point pressed against the rubber stopper (c) ; i t rests firmly, so that the cover of the desiccator containing it may be taken off and even inclined without the stopper falling out, On the bottom of the weighing glassis placed a round table made of platinum sheet and provided with three legs. FIG. 1. FIG. 2. a FIG. 3. When the platinum crucible with the hygroscopic substance (for example, La203) has been heated to a yellow heat, the desiccator is pre- pared as seen in Fig.2, the lid taken off, and the still red-hot crucible placed on the platinum table (h) in the weighing glass, which prevents the glass from coming into direct contact with the red-hot crucible. The cover (a), which was taken off only for a few seconds, is replaced, the expanding hot air leaves the desiccator through the drying-tube (d dJ, and, on cooling, dry air passes in through the same way, so that the atmosphere of the desiccator is in equilibrium with the outer atmo- sphere. Then the stopper is pushed into the weighing glass so as to almost close it, which is done completely after a quarter of an hour,ATOMIC WEIGHT OF LANTHANUM.1257 when all has cooled down. After this, the cover of the desiccator is turned back through 90”. The substance enclosed inside the weighing glass cannot attract, moisture from anywhere. The surface of the phosphoric oxide inside the desiccator must be renewed very often and fresh oxide added. The crucible was weighed regularly half-an-hour after being placed in the desiccator, and a weighing glass of the same size as that just described containiog a similar platinum crucible treated in the same way was used as a tare on the right hand pan of the balance, both weighing flasks having nearly the same weight and displacing nearly the same volume of air, so that their coefficient of surface condensation was equal in both cases. The weighings were made on a very fine and sensitive balance made by Rueprecht, and reconstructed for this kind of work by Nemetz, of Vienna.The balance was guarded on all sides against the influence of radiant heat, and as fractions of a gram could be placed on the balance without the case bsing opened, the change of the “ zero-point ” or of the ‘‘ state of the balance ” (Mendelbeff) was only very small. The “ zero-point ” was not taken with the empty balance but with carefully adjusted 50 gram weights on each pan, this being very nearly equal to the weight of the weighing glass plus crucible. The method of vibrations was used, and the weights employed were most carefully calibrated, so that the errors due to weighing alone hardly exceed & 0.00002 gram. This physical error is quite insignifi- cant compared with the much greater error due to the inexactnesss of our chemical methods.When by using the desiccator just described the attraction of moisture by the enormously hygroscopic lanthanum sulphate was reduced to a minimum, higher numbers were obtained for the atomic weight than in the first series. This is seen by comparing the results of experiments 17 and 19 obtained by Mr. Pavlf6ek by the old method of weighing, giving La= 138.73 and 138.79, with experiments 16 and 18 made by me, which yielded La= 138.98 and 138.93. The results of this second series of syntheses are seen in Table I11 (p. 1258), and they require some explanation. In order to be able to compare the data obtained in the different phases of the single experiments with those obtained by other chemists, the weight obtained by weighing in air are given in Table 111, from which the ‘‘ apparent ” and I‘ true ” atomic weights are calculated. For the final determinations of the atomic weight of lanthanum, the reduction to a vacuum was calculated by using the following data.Density of La20,=6*48, that of air in our laboratory d=1.18 (1 litre = 1.18 grams), one gram La,O, displaces 0.182 mg. ol air or one gram in air weighs in a vacuum 1.000182 grams. Density of1255 RRAUNER AND PAVLfcEK: REVISION OF THE TABLE: ILL-Syntheses of Lanthanum SuZp?ute. Xeconnd Series ( VeigAts in Air). La La I d Lac La: La4 1.7024 1.0244 1'0654 1-00671 1'06461 I '2862: grams. grams. grams. ~ _ _ _ _ _ _ _ 1.95834 0*83301 - 1'95809 0 '83276 - 1'95733 0 '53200 - - 0'83200 - 0'0034' 2.96305 1 '26059 - 2'96227 1.25981 - - 1'25981 - 0.0061! 1'82295 0 -79862 - 1.78178 0.75737 - 1.78168 0'75727 - 1.78001 0.75560 - 1 *77884 0.75443 nil 1.85312 0.78769 - 1.85125 Om572 - - 0.78572 - 0'00132 1.74803 0'74127 - 1'74742 0*740(16 - - 0'74066 + 0.0005E 1.84850 0.78381 - 1 '84820 0.78351 - - 0-78351 + 0.00028 2.23795 0'95168 - 2.23419 0'94792 - - 10.94792 +0.00074 - so3 cor- rected grams Temp.51 0" 1 day 560" 2 hours 560" 7 honrs - 500" 7 hours 560" 6 Iionrs - 300" 1 day 500" 5 hours 550" 8 hours 6 hours 7 hours 4 day 24 days 634"+_ 00-634' 34-654' 0 0 - 6 34' 34-654' - 1 day 654"+ 1 day 634"+ 1 day 654"+ 1 day - - 34-654' 2 days > 654"k 1 day - k Mean in air .............................. j 7 -5 93 1 Probable error of the percentage ...+_0*00076 At. wt. of La. ent. 138.23 138.28 138.43 - 138'17 138-29 - 130.0 138.42 138'44 138.80 - 138.43 138.82 - 139'10 139.24 - 139.125 139 19 - .38*31 .38.96 - La = - True. - - - 39.097 - - 39.087 - - - 39 *065 - - 39-097 - - 39,112 - 39.128 - 39 *082 39.095 -- -ATOMIC WZIGITT Oh' LANTHANUM. 1259 La2(S0,), = 3.545, one gram in air weighs in a vacuum 1-000333 grams. The vacuum numbers with all other corrections are given in Table IV. TABLE IV.-Final Detei-minations of the Atomic Weight of Lantlmnum (Weights in Yacuo). No. of fraction. La0 La0 La1 La1 La1 La4 La7 - No. sf experi- men t. 23 24 20 21 22 26 25 1.06562 1.00694 1 *I 2553 1.70276 1'02460 1.28650 1-06488 1'85054 1.74856 1-95457 2'95707 1'77943 2'23419 1'84910 ~~ ~ SO3 grams. 0.78492 0.74162 0 92904 1'25431 0 *7 5 483 0.94769 o m 4 2 2 Mean .........., Probable crroi 57 5842 67-5568 57.5545 57 $528 57'5802 575823 57.5891 57.5543 f 0,0007 I 139'036 139.053 139.038 139'026 139.009 139'024 139.065 139.036 The atomio weight of lanthanum corrected to a vacuum is therefore La = 139.04. In all experiments recorded in Table 111, the temporature to which the ljulphate was heated was stated as nearly as possible. It was found that even at 560°, and when the heating was carried out in an atmosphere of immonium carbonate, the acid sulphate could not be destroyed completely, and the '' apparent " atomic weight of about 138.4 was obtained ; this is identical with that found by several investigators who overlooked the presence of the acid sulphate.If, however, a larger mass of the sulphate had to be heated, the inner part gave off this half-combined " sulphuric acid less easily than when the mass of the sulphate was smaller, so that, for example, with 1.82 grams of the sulphate the value 138.42 (experiment 29) was ob- tained, whereaswith 2-96 grams this had fallen to 13899 (experiment 21). The attempt was made to heat the lanthanum sulphate to such a high temperahre that some basic sul'phctte might be formed, in order to see whether the same atomic weight would be obtained when the titration was done from the bmic side, instead of from the acid side as hitherto. For this purpose, the smaller crucible was heated inside a larger platinum crucible to a dark red heat. It was found that the sulphate assumes a visible dark red heat near the temperature a t which pure potassium iodide melts, that is, 634O f 3 O (Carnelley), whereas a stronger red heat corresponded to the melting point of silver sulphate, that is, to 6 5 4 O f 2O.neutral sulphate" was When this mode of heating was used, a1260 BRAUNER AND PAVLf6EK: REVISION OF THE obtained only in experiment 22, and basic sulphates were' obtained only in experiments 24 and 25. On titration with N/20 sulphuric acid until all basic salt had dissolved and the neutral point was reached, the same result was obtained as when the free acid was titrated with N/30 sodium hydroxide, This agreement shows that the final residue of '' half-combined '' sulphuric acid is present in the form of the acid sulphate, and not of that of the pyrosulphate.It is also seen from the above experiments that normal lanthanum sulphate may be heated t o a dark red heat without decomposing, for its slight decomposition begins only at about 650°+_, and even near this temperature the decomposition of the acid sulphate is not com- plete. From Table IV, it is seen that the largest deviations from the mean atomic weight are +0.03 and - 0.03, and the probable error of the percentage of the oxide in the sulphate is +,0-0007, so that the lanthanum material employed may be considered homogeneous. With regard to the circumstance that the oxide obtained from fraction La7 was slightly buff-coloured, as compared with the white oxide obtained from the most basic fractions Lao, Lal, La2, La3, and La4, the possi- bility that the fraction La7 contains a trace of an impurity which also very slightly raises its atomic weight, is not excluded, but even if this experiment 25 and the too low result of experiment 22 be omitted, the mean atomic weight La = 139.04 would remain unchanged.On the contrary, the lower fractions may be regarded as containing the real p r s hnthanum. This question was tested with a more negative and less intensely purified fraction A5 + 6. Experiment 27.-0-90238 gram La,O, gave, after heating the sul- phate for 2 days at 634O k, crude sulphate = 1.56694 gram (apparent atomic weight =139.07). The sulphate was acid, and the correction - 0*00056 gram, therefore SO, = 0.66400 gram. La,O, in the sulphate = 57.609 per cent., from which La= 139.20 (in air). This result agrees with t h a t obtained in experiment 14 of the first series, and shows that the assumption of the presence of an earth with a higher atomic weight in the less basic fractions of our lanthanum material beginning even with La7 is not wholly unfounded.The present series of experiments, however, did not confirm the slight variation of the atomic weight obtained from the lower frac- tions in the first series of experiments. The lower numbers obtained in that series, especially with the fractions La1 and La2, and the circum- stance that the discrepancies between the first and second series gradually diminish was found only after a long time to be due to the following reasons : The water vapour (1) The highly hygroscopic nature of the salt.ATOMIC WEIGHT OF LANTHANUM.1261 which was attracted by the salt from an atmosphere of ammonium carbonate is given off again by the salt only after being heated for many hours a t above 600”. If we stop this heating too early, the weight of the sulphate will be found greater, and the atomic weight smdler, than the truth. The same error is caused if the anhydrous sulphate is left in an ordinary desiccator, especially if it does not con- tain fresh phosphoric oxide and if no precautions are taken to avoid the attraction of moisture during the weighing of the salt. These two sources of error were eliminated only during the second part of the research by using the special form of desiccator. (2) The titration of the acid sulphate in the presence of ethyl- orange is not only an acidimetric, but also a colorimetric method, which requires a well-lighted laboratory and good practice.Both were want- ing during the first stage of our work. The use of this method undoubtedly lowers the standard of exactness of our work, for whereas the weight of the sulphate can be determined to +0*00002 gram, the .acidimetric-colorimetric method hardly allows an exactness equivalent to +0*00005 gram of sulphuric acid to be reached. It is an interesting psychological fact that wilh increasing practice the sum of the errors due to the above sources gradually diminished, so that the results obtained during the latter part of the first series are quite free from them. This is especially the case with experi- ments 9, 10, 11, 12, and 13, which give a mean atomic weight almost identical with thatl obtained in experiments 20-26, but they are not included in the final calculation, as they would raise the value of the probable error of the mean from +_ 0*00073 to f 0-0012, and lower the “weight ” of our atomic number.But the direction in which the errors of the first series diminish may be regarded as a proof that our present number, La = 139.04, lies near the truth. Second Method of Atomic Weight Determination. Analyses of Lccnthanum Conversion of the anhydrous sulphate into the oxide by calcination was the method used by Marignac, in 1873, who obtained in this way La=138*81 (see Table I), and the same method was used later on with scandium, thorium, and cerium (Nilson, Kruss, Brauner). The residues from the above two series of experiments were purified from alkali, &c., in the manner already indicated, and the anhydrous sulphate of lanthanum was prepared.It was dissolved in 5-6 parts of ice-cold water in a platinum dish plunged in ice, but instead of crystallisation being effected by heating to 35-40’ (Mosander, Bunsen), the ice-cold solution was stirred until the hydrated salt had separated out, after which it was allowed to assume the ordinary temperature. Sulrphate. New Hydrate of Lanthanum Xulphate.12G2 BRAUNER AND P A V L ~ ~ E K : REVISION OF THE The salt was collected by suction on a perforated platinum plate, washed well with cold water, and dehydrated a t 500-600O. By re- peating this process of recrystallisation ten times, the fractions P I to P I 0 were obtained from the original sulphate P.During these experiments, in which I was aided by Mr. Picek, we observed that the proportion of the sulphate remaining in the filtrates was not always the same, and, similarly, the character of the sulphate was different. The sulphates, P4, P6, P7, and P10, consisted of fine needles, others formed distinct, prismatic crystals resembling the enneahydrate. The salt P4 was especially characteristic as forming flocks like alumina, consisting, however, of the finest needles. It separated out at 0-1"; it was quickly collected on the pump, pressed between smooth paper, and the dry powder immediately weighed in a closed platinum crucible. Experiment 28.-1.93822 grams of the salt P 4 gave, on drying at 500", a residue of 1.28710 grams, and on further drying for 8 hours at 550" f , of 1.28663 grams of the anhydrous salt, from which it is seen that lanthanum sulphate parts only with great difficulty with the last traces of its water of crystallisation.The loss of weight, which in this case can only be due to loss of water, was 0.65159 gram, or 33.618 per cent., which is equivalent to 15.92 mols. The remaining 1,28663 grams of the anhydrous sulphate were very gradually heated to a yellow heat, and yielded 0.74122 gram of La,O, = 57.6103 per cent. In order to ascertain whether the weight of the oxide remained constant, the product was heated again for 1 hour over the blow-pipe. Its weight became 0.74153 gram, that is, it became heavier by 0*0003 gram. On further heating, the weight decreased to the minimum of 0.74123 gram (compare experiment 29).It is evident from the abovs that the hydrated salt analysed is a new hydrate of lanthanum sulphate, the hekkaidekalbydrate : From this, La = 139.207. Calculated. & Found. La,O, = 326.1'7% 38.17 38.24 350, = 240.18 28.10 28.14 16H,O = 288.24 33.73 33-62 854.59 100.00 100*00 - -- Muthmann and Rijlig (Ber., 1893, 31, 1723) say that the ennea- hydrate ( +9H,O) is formed at all temperatures, and that they endeavoured in vain to obtain another hydrate, so that the existence * The atomic weight '(iu sir" is used here.ATOMIC WEIGHT OF LANTHANUM. 1263 of the new hydrate is not devoid of interest. (The hexahydrate crystallises only from an acid solution.) Mr. Picek tried to determine the solubility of the hekkaideka- hydrate and its transition temperature into the enneahydrate, but we only learned that the system, hekkaidehydrate -+water, is a very labile one, even at a temperature near 0'.It undoubtedly originally consisted chiefly of the hekkaidekahydrate ; it was well drained on the pump and kept in a covered platinum dish. Next day it was found to be very moist and converted completely into the ennea- hydrate. Experiment 29,-1-96466 grams of the air-dried salt gave 1.51969 grams after heating for 10 hours a t 530°, and, after further drying for 6% hours at 600°+, ,la51947 grams, showing that the last 0*00022 gram of water was retained very strongly. The loss of weight, 0,44519 gram, amounts to 22-66 per cent., the calculated amount for 9H,O being 22.26 per cent. On raising the temperature gradually to the highest yellow heat obtainable with the blow-pipe, this salt was found to lose its sulphuric acid with great difficulty, and all attempts to obtain an oxide of a constant weight were fruitless : For a second experiment, the salt P10 was used, Time of heating.4 day over the blow-pipe ............. *day I 1 ............... 1 day 93 ............... S& hours ,, ............... 10 minutes at yellow heat ............... 2 hours over the blow-pipo 4 hour at almost white heat ........... 9 ) 9 9 9 9 ............ Wej6ht of residue 111 grams. - - - I- 0 9575t 0 '87937 1 0.57521 I 0'87649 0.87586 1 0.87645 '1 0.87571 Apparent atoinic weight of La. 180.6 140.9 139.192 139.70 139 '43 139.68 139.38 I n the last instance, the temperature was so high that the two crucibles were nearly soldered together.It is seen from experiments 28 and 29 that the above simple method, which gives excellent results with such weak bases as CeO, and Tho,, cannot be used with the strong base La203.' But even when the minimum weight was reached by a chance, the oxide was heavier by 0*00012 gram than required by theory. T. W. Richards has found that oxides obtained from the sulphates 6' occlude " a larger quantity of gases than those obtained by heating the oxalates. Lanthanum oxide obtaiued from the oxalate is voluminous and almost white, that obtained from the sulphate is denser and greyish-buff in colour. The fact that after ten recrystallisations from its aqueous solution1264 BRAUNER AND PAVLICEK: REVISION OF THE the sulphate is perfectly normal and not even slightly basic, shows that the amount of its hydrolysis in a cold aqueous solution of the above concentration must be quite inappreciable.Experiment 30. -This shows that on heating lanthanum sulphate t o the highest temperature obtainable with a Bunsen burner (without blast) it loses easily two-thirds of its SO,, and a new basic sulphate Ls20,,S0,, stable a t a higher temperature, is obtained. 4.0867 grams of the anhydrous sulphate, obtained by synthesis from 2.3535 grams of the oxide, yielded, when heated as above, a residue weighing 3.2044 grams, which when heated to a still higher tempera- ture decreased to 3.9146 grams of the basic sulphnte. From this SO,= 0.5611 gram, an amount approaching that required for 1S0, = 0.6777 gram.An analogous phenomenon was observed by me in the case of praseodym sulphate.” The above two experiments show that the true atomic weight of lanthanum cannotlie higherthan 139.20 (in air) or 139.14 (in a vacuum). No indication of a ‘(lanthanum ” with the low atomic weight, 135, was found in our purest lanthanum material. Third Nethod of Atomic Weight Determination. I n 1882, Stolba (Ablmndl. Konigl. Bohm. Gea. Visserzsch.) proposed a new method for the determination of the atomic weight of lanthanum and other rare earth elements (Ce, Di). I n one part of the dry oxalate the percentage of R,O, (or CeO,) is determined by calcination, and in another that of C,O,, with permanganste in sulphuric acid solution.? This method was described for a second time as new by W.Gibbs in 1893 (PTOC. Amer. Acud., 28, 260). Lanthanum material was purified by Shapleigh by the Mendelbeff-Auer method, and the oxalate washed with a large quantity of hot water. The oxalates were dried on a water-bath and then thoroughly mixed. The mean atomic weight of lanthanum found by this method by Gibbs was La = 139.70. Gibbs states that Dr. Shapleigh found, with the same material by the sulphate method, La = 139.71. Stolba’s method was used by me with very good results for the determination of the atomic weights of cerium, thorium, and praseodym, and I thought, therefore, that it might serve a s a method OF control in the case of lanthanum. But it was necessary to consider the question whether the lanthanum material used by Gibbs really contained an * This fact was communicated t o the Chemical Society on February 24, 1902.Later on (Compt. rend., 1902, 134, 657), basic sulphates of Pr and Nd of the same formula R,O,, SO, were described by Bfatignon. My discovery was made indepen- dently of that author. .t. In this paper, Stolba finds for the first time that lanthanum oxide may be deter- mined alkalimetrically with R good result.ATOMIC WEIGHT OF LANTHANUM. 1265 earth with a much higher atomic weight, or whether the composition of his oxalate was abnormal. The fractions Lao-La7 into which our purest Ianthanum material had been divided were thrown down as oxalates by adding an excess of pure oxalic acid t o a hot dilute solution of lanthanum nitrate. After pour- ing off the supernatant liquid, the precipitate was digested with oxalic acid solution.A perforated, round, platinum plate, 2 cm. in diameter, covered with a slightly larger piece of smooth, round filter paper, was used for collecting the oxalate on the pump. It was washed, first with dilute oxalic acid solution, then with cold, tepid, or hot water, which mode of washing has an influence on the composition of the precipitate, as will be noticed further on, and finally with pure alcohol rectified in the presence of tartaric acid. Oxalates prepared in this way may be obtained perfectly air dry and homogeneous after standing for a few hours in the open air (covered with paper), an important circumstance when different portions are to be weighed out for different determinations. These conditions are not fulfilled when the oxalates are dried on the water-bath as recommended by Gibbs. In converting the oxalate into the oxide, i t must be heated very gently and gradually, beginning from the lid in order to avoid a loss of the fine powder which is easily carried away with the escaping gases, It appears, however, that it is sometimes difficult to obtain a, perfectly pure oxide as soon as its quantity exceeds 1 gram and the u personal error ” due to two different observers may not be without influence on the slight deviations in the percentage of oxide from the same oxalate.For the determination of the oxalic radicle, C,O,, the oxalate was heated in an Erlenmeyer flask with 50 C.C. of 12 per cent. sul- phuric acid and titrated with permanganate, with special precautions into which I cannot enter here.The permanganate was standardised many times with ammonium oxalate under exactly the same condi- tions, The salt was repeatedly recrystallised from hot water, finally in the presence of free ammonia, in order t o prevent the formation of the acid salt, The results are given in Table V (p. 1266). The differences between the atomic numbers obtained are very con- siderable, being equal to a maximum of 1.25, and yet after excluding the abnormal results obtained with fraction La4 a mean value La= 139.07, is found, identical with the true atomic weight of lanthanum. The differences are due to the different composition of the individual oxalates, and this depends on the temperature of the water used for washing them. With an increase in the temperature of the water, the quantity of the water of crystallisation of the oxalates is found VOL.LXXXI. 4 P1266 BRAUNEK AND PAVLICEK: REVISION OF THE 31 32 33 34 35 36 37 38 La0 La1 La2 La3 ~ 4 1 La5 La6 La7 TABLE V.-Analyses of Lanthanum Oxalate. Lanthanum oxalate grams. (a) 2.27247 (b) 2.14773 (c) 0.67462 (a) 2.0854 (b) 1'8823 (c) 1.92285 (d) 2-51643 (e) 3'80470 (f) 1.60083 (a) 1'7485 (b) 1'7983 (c) 1.30665 (a) 2.2325 (b) 1.14021 (a) 2.12661 (b) 2.565091 (c) 1'24241: (d) 1 .08010: (a) 1.9488 (b) 0'89926 (a) 2'0880 (b) 1-9684 (c) 1'41521 ( 6 ) 2-0111 (c) 2.21199 (d) 1'13639 (a) 1'9753 1.06E43 1*00676 0.93205 0'8416 0.85993 1.12533 1'70246 0-7847 0.80645 1.0760 1.06831 1 '28627 - - - - - - 0.8721 0.9755 0'9188 - - 0.9507 0.9677 1 '06469 - La,O, per cent 46.884 46-876 44.722 44-711 44 '694 44.719 44.746 44.879 44-845 48.197 50.2351 :50.145] - - - - - - 44.751 46.719 46'678 48.129 48'118 48.133 - - - - c203 gram.I - 0-20941 - I - - - 0 '47097 - - 0'38879 0.36395 - - - 0.413681 0-360171 0.26698 - - - 0 '43706 - - - 0.36094 c20, per cent - - 31.041 - - - - - 29'673 - - 29.755 31.920 - - - :3 3 -29 71 13 3 '3 4 61 29.689 - - - 30.883 - - - 31.762 Ratio used for calcula- tion. a : c b : c - a : f b : f c : f d : f e : f - a : c b : e - a : b - CL:C a : d b : c b : d a : b - a : C 6 : C - a : d b : d c : d - Atomic weight * La = 139.12 139.09 138.77 138.74 138'67 138-76 138.86 138-90 138.77 139.07 :138*94 1138.70 113 8 *65 :138'41 138-79 139'38 139.24 139.65 139.61 139'66 - - - - - - - Mean atomic weight after rejecting the results of experiment 35 (La4), 139.07.* When 0=16, C=12*00, and N=14.04. to diminish and the atomic number to rise, as is seen from Table VI (p. 1267). The abnormal composition of the oxalate is most prominent in fraction La7, which yielded the atomic number La=139$6. The oxalate was mashed with hot water, and formed a heavy, crystalline powder. It must have consisted partly of a basic oxalate, which was probably formed by the hydrolysis of an oxalonitrate.ATOMIC WEIGHT OF LANTEANUM. TABLE VI.-Showing the Pewentage Co?izposition of Frccctions of Lanthunuum Oxalccte, &c. Fraction. ~ Lal. 1 La5. I-/- - L22. 44.86 29.76 25.38 10-24 t38.77 138.90 La6. 46.70 30.88 22'42 8.69 139-24 Lao. 46.88 31 -04 22.08 8 *53 139 09 139'38 139.12 La7.~ 48.13 31 -76 20.11 7.57 139'61 139'66 1267 -- I 48'20 ~ [50*19] 31-92 I [33-321 19'88 [16'49] 7.47 ~ [5'95] 139~07 [138'41] - /[138.941 As this number is identical with that obtained by Gibbs, namely, La = 139.7, from an oxalate which was prepared exactly in the same way, i t is unnecessary to assume that this number represents the real atomic weight of lanthanum contained in the material used by him. On the other hand, the abnormally low results obtained in our series from the oxalates washed with cold water, namely, Lal, La5, and La6, point t o the presence of free oxalic acid in the oxalates used, undoubtedly due t o absorption. A normal atomic number was obtained, probably by chance only, from the fractions La0 and La3. An examination of the same lanthanum material which, in Dr.Shapleigh's hands, gave the abnormally high number La= 139.7 by the sulphate method, and which was presented to me by him, has shown that this material is not quite free from foreign earths, especially from traces of the constituents of didymium, so that even this high number finds an explanation. It is seen from Table VI that pure precipitat,ed lanthanum oxalate very probably contains 11 mols. of water, as stated by Wyroubnff (Bull. Soc. frccng. Nin., 1895, 24, 110), who also prepared an oxaIate with 3H,O. I obtained (Trans., 1898, 73, 974) by crystallisation from dilute sulphuric acid an oxalate with 7H,O, but the existence of a salt with 9H,O as found by Czudnowicz and Cleve becomes improbable. It would seem that in fraction La4 an oxalate with 6H,O was present.Is Lanthanum a Mircttme of Elements 1 The results of the present investigation enable me to answer this question as follows : (1) Lanthanum material purified (a) by fractional crystallisation and recrystallisation of its soluble salt with ammonium nitrate (Mendelkeff- Auer), ( b ) by fractional fusion with potassium and sodium nitrates at 4 P 21268 BRAUNER AND PAVLICEK: REVISION OF THE 450-500' (Debray-Schiitzenberger), and (c) split up into eight dif- ferent fractions by partial precipitation with potassium hydroxide, contains only ofie element, the true lanthanum with the atomic weight La= 139.04 in a vacuum. The least basic fractions (especially La7) may contain a slight admixture of an element with a higher atomic weight which gives to the oxide a very pale bnff tint, but this very small quantity has scarcely any influence on the atomic weight.(2) An element with the atomic weight 135, which was presumably found by some chemists, lastly by Schutzenberger in 1895 in some fractions of lanthanum, is not contained in the pure lanthanum or in any of its side fractions, and it must be definitely stated that this low number could only be obtained from fractions which contained yttria, as shown by my chemical and optical experiments. (3) With regard t o the fact t h a t the least basic fractions, obtained from our lanthanum material by the second method of fractionation, yielded by the correctly applied sulphate method the numbers Rxxx = 139-27 (experiment 14) and 139.20 (experiment 27), whilst the solution of this earth was perfectly free from any earth possessing a n absorption spectrum, the conclusion may be drawn that in these fractions a small quantity of an element with a higher atomic weight than that of lanthanum is present.This fact stands in the closest relation with that discovered by me twenty years ago (Monatsh., 1882, 3, 486), that on fractionating the mixture of lanthanum and old didymium with ammonia, intermediate fractions, less basic than lanthanum, are obtained containing an element with a higher atomic weight than that of lanthanum. The numbers obtained from these fractions were R1=140.19 and the maximum R1"= 140.63. I n the spark spectrum, new lines not belong- i n g to lanthanum were observed. These experiments were given up at that time for this reason: Cleve (Bull.SOC. Chim., 1883, 30, 289) declared dith the whole weight of his authority that between lanthanum and didymium no third element is contained. In this conclusion he was evidently wrong, and the question requires a new and thorough investigation, Critical Remarh. On casting a glance a t the atomic weight determinations collected in Table I in the introduction, the following explanation of the dis- crepancies may be offered. (i) The determinations by Rammelsberg and Marignac (l), (2), and (3), and Holzmann (1) are founded on the precipitation of barium sulphate, which carries down a considerable quantity -of lanthanum sulphate,ATOMIC WEIGHT OF LANTHANUM. 1269 (ii) Holzmann’s determinations (2) and (3) are made from somewhat complicated salts. (iii) As regards the determinations of Czudnowicz and Erk (2), see (i). (iv) Hermann’s determinations (lj, (2), and (3) are very near the truth but a little high, probably because his lanthanum was not freed from its higher companion. (v) The numbers of Zschiesche, Erk (l), and Erk (2) are too low, very probably owing to the presence of yttria. (vi). Marignac’s number (4) is too low owing to the very hygro- scopic nature of the anhydrous sulphate and incomplete expulsion of water from the anhydrous salt. (vii). Cleve’s number (1) is identical with that obtained by us from the fraction A5 + 6, see also (iv). (viii). The numbers obtained by Gibbs and Shapleigh have been explained in an earlier section of this paper (p. 1267). (ix). The low numbers obtained by Brauner (1) and (2), Cleve (2) Bauer, Bettendorff, and probably by Schutzenberger and Muthmann (although the last two chemists give no details about their work) are due to the formation of some acid sulphate and to the very hygroscopic nature of the anhydrous sulphate. Having shown that the majority of the determinations of the atomic weight of lanthanum hitherto made are inexact, either because the material used was not quite pure or homogeneous, or because the method used for the determination was not free from error, the following important question arises : Are we entitled to use the whole series of determinations hitherto made for the final calculation, or may we not regard the number resulting from the present minute and detailed work, namely, La=139*04 as lying near the true atomic weight of lanthanum, awaiting, of course, its confirmation by other methods ? I n conclusion, I may say that, having extended the research t o other rare earths and their sulphates, I find this : Ali atomic weight determinations of the rare earth elements made by the synthetical sul- p h t e method &ring the nineteenth century are vitiated by an erq‘or which tends to lower the atomic weight and diminishes as the basicity of the earth decreases. If the atomic weight of lanthanum is La= 139.04, it is highly improbable that cerium would possess the same atomic weight, Ce = 139, as assumed by Clarke from the result of the work of Wyrouboff and Verneuil, who obtained for a ‘‘ bivalent ” cerium the value Ce = 92.7. This assumption has been proved to be correct by work specially done in our laboratory. ’

ISSN:0368-1645    

DOI:10.1039/CT9028101243

出版商:RSC    

年代:1902

数据来源: RSC