摘要:

78 XI.-On, Citric Acid as a Constituent of the Juice of Unrt$e Xulberries. By C, R. ALDER WRIGHT, D,Sc., and GEO. PATTERSON. THROUGH the kindness of Dr. Hardwicke, coroner for Middlesex, we obtained a quantity of the juice of mulberries grown in his garden a t Hendon. The fruit did not appear to ripen this year as fast as usual, so that, before it was fully ripe, an early frost almost stripped the tree of leaves, leaving bushels of berries not quite fit for eating. The juice of these was expressed, and constdxted a somewhat turbid light brown fluid of very acid taste. On keeping in a loosely corked phial, it became mouldy on the top, and developed a small quantity of alcohol. On qualitative examination, it was found to contain a considerable amount of mucilaginous matter, precipitable by addition of an equal volume, or rather more, of strong alcohol. The filtrate from this, when boiled down so as to expel the alcohol, and neatralised with ammonia, gave no precipitate with calcium chloride in the cold, but on boiling for half an hour threw down a sandy calcium salt.The concentrated filtrate from this (containing excess of calcium chloride and rendered alkaline by ammonia) deposited no more precipitate on further boiling, butl on addition of alcohol an amorphous lime-salt was thrown down. From these observations it appears that whilst oxalic and tartaric acids were absent, or present in insignificant quantity only, citric acid was present to a considerable extent, and apparently also malic acid. A volatile acid, presumably acetic acid, was also found in minute quantity.Fehling’s solution was easily reduced on boiling. To determiue approximately the citric acid, a known quantity of juice was boiled with ammonia and a recently boiled and filtered mix- ture of calcium chloride and ammonia, until no further precipitate was occasioned in the filtered liquid on further boiling ; the precipitated calcium citrate was collected and washed with a minimum of water till the washings were free from chlorine, then dried, and determined as calcium carbonate by ignition, and treatment of the residue with ammonium carbonate. The filtrate was treated with twice its volume of alcohol, and the precipitated gelatinous lime-salt collected, washed with 60 per cent. spirit, and weighed as carbonate. The ash left on incineration was dissolved in hydrochloric acid and treated with am- monia, whereby a precipitate mainly consisting of phosphate of calcium was thrown down ; the lime in the filtrate from this was determined as oxalate, and the potash in the filtrate by platinic chloride after evaporation to dryness and ignition.The following numbers were obtained :-WRIGHT AND PATTERSON ON CITRIC ACID, ETC. 79 Grams per litre. Citric acid, 25 C.C. gave 0.524 CaCO, = 0.6707 C6H807 = 26.83 Malic acid, ,, 0.146 ,, = 0.1956 C4H605 = 7.82 Glucose, = 0.0685 glucose = 2.74 Ash, 0.0330 was phosphate of lime, &c., pre- 0.0140 was CaC0, .................... 0.56 0.10G5 ,, N&CO3, silica, and matter un- 25 C.C. reduced Cu20 containing 0.1220 Cu 25 C.C. gave 0.2350 total residue, of which cipitated by NH,.............. = 1.32 0.0815 ,, K2C03 .................... 3.26 determined ................ 4.26 9.40 Other constihents, mucilage, pectin, &c., &c. ........ 23.3 7 0,2340 Total s0Zid.s (25 C.C. gave 1.754 grams after drying for about 24 hours at loo", till almost constant in weight).. .................................... = 70.16 0.27 anhydrous citric acid, C6HS0, .................. 28.14 In order to confirm the presence of citric acid, the juice was boiled with marble powder, and the organic lime-salt formed washed and decom- posed by sulphuric acid. In this way citric acid was readily obtained. The calcium salt of the acid thus isolated was prepared by neiitralising with ammonia, adding a filtered boiled mixture of calcium chloride and a<mmonia, boiling, and well washing the sandy precipitate.After drying at 100" till constant, the following numbers were obtained :- 0.3950 gram dried at 150-160" lost 0.0330 = Calculated for ( C6H507)2Ca3,'LH20. ....... = 6.74 ,, 0.361 gram of dried residue gave 0.293 CaS04 .......................... Ca = 23.87 ,, Calculated for ( C6H507)2Ca3 ............ = 24.09 ,, - VoZatiZe acid (reckoned as acetic acid) .............. TotaE acidity, determined by titration and reckoned as 8.35 per cent. According to Warington (this Journal, 1875, 925), citrate of cal- cium dried at 100" contains 5.91 to 7.68 per cent. of water of crystal- lisation, or approximately 2H20. According to some text-books, however, the salt when dried at 100" is (C6H507)2Ca3,H20. It results from these numbers that whilst unripe mulberry juice is not as rich in citric acid as lemon and lime juice (which contain 8 to 12 ounces per gallon, or 50 to 75 grams per litre of crystallised acid, or 46 to 68 grams per litre of anhydrous acid, C6H807-Warington,80 TILDEN ON THE RYDROCARBONS OBTAINED FROM Zoc. cit.), it is still sufficiently rich to be a notable source of t,hat acid. From this circumstance, and the presence of considerable quantities of potash, it seems probable t<hat the juice of imperfectly ripe mulberries may be found to be vahable as an antiscorbutic, and as a substitute for lime juice.

ISSN:0368-1645    

DOI:10.1039/CT8783300078

出版商:RSC    

年代:1878

数据来源: RSC

摘要:

80 TILDEN ON THE RYDROCARBONS OBTAINED FROM XI1.- On the Hydrocarbons obtained from the Pinus Sylvestris, with Remarks on, the Constitution of the Terpenes. By WILLIAM A. TILDEN, D.Sc. (Lond.). I. Russian Turpentine Oil. SOME months ago, by the kindness of Dr. Armstrong, I received a quantity of Russian turpentine oil, with the information that it would distil chiefly between 168" and 180°, that is a t a temperature considerably above the boiling point of the terpenes of ordinary Ameri- can and French turpentine. The sample contained a small quantity of acetic acid and empyreu- matic products, and thcre can be no doubt, therefore, that this oil is obtained, not from the natural exudation from the living tree, but as a bye-product during the distillation of the wood for the purpose of preparing tar, as practised extensively in the north of Europe. Ac- cording to H a n bury and Fluckiger (Pharmacographia) the trees used for this purpose are chiefly the Pir~us syhestris and Pinus Lede- bourii.The Russian turpentine oil as it came into my possession had the specific gravity 0.8682, and 100 mm. of the liquid, t'ested by Wild's instrument, using the soda flame, were found to rotate the polarised ray about 17" to the right. It has a yellowish colour, and a peculiar pleasant odour, quite distinct from that of common turpentine oil. After sLaking with solution of caustic sr;da to remove acetic acid and creosote, the oil was submitted to fractional distillation, the frac- tions uItirnately obtained of nearly constant boiling point, being finally distilled once or twice from sodium.There are four principal ingre- dients in this turpentine- 1. The most volatile constituent is a terpene boiling at the same temperature as australene (from American oil), but its action on the polarised ray is much greater t*han that of australene. 100 mrn. give a rotation of + 23.3". There can be no doubt, however, that it is identical from a chemical point of view with austlralene, since itTHE PINUS SYLVESTRIS, ETC. 81 behaves in the same manner as that hydrocarbon when acted upon by nitrosyl chloride gas. This terpene constitutes 10 to 15 per cent. of the turpentine oil. 2. A second terpene present in Russian turpentine oil is an entirely different substance. After a most tedious series of fractionations and examination of the products, I have come to the conclusion that the pure hydrocarbon boils under ordinary atmospheric pressure at 171", or thereabouts.A considerable quantity of it, boiling at 171" t o 171*5", was collected. It possesses a characteristic odour. 100 mm. rotate the polarised ray 17" to the right. It gave by combustion 88.09 per cent. of carbon, and 12.14 of hydrogen, and by Hofmann's process a vapour density =65*8 (H = 1). The formiila ClOHl6 requires 88.23 per cent. of carbon, 11.76 per cent. of hydrogen, and vapour density 68. This terpene occurs in the turpentine oil to the extent of about two- thirds of its volume. The product I have just described is, I believe, as pure as it is possible to get it. Nevertheless, I think it contains traces of cymene, a hydrocarbon of which this turpentine contains a considerable quan- tity, and from which it would be very difficult to separate it com- pletely, in consequence of their boiling points lying so close together.3. Cymene was isolated by the usual process from the two fractions boiling at 1'72-173" and 173-175". These were mixed together. A portion of the mixed liquid was oxidised by chromic acid, when it gave about 3 per cent: of a mixture of toluic and teTephthalic acids. The rest was divided into two portions. 50 C.C. were cooled by ice and salt, and then mixed very gradually with more than an equal bulk of oil of vitriol. After standing for twenty-four hours the mixture was diluted, and from the separated oil a quantity of cymene was obtained equal t o about 79 per cent.by weight of the liquid operated upon. The second part of this liquid, consisting as it did mainly of the new terpene, was submitted t o the action of bromine in order to re- move if possible two atoms of hydrogen and convert it into cymene. In order to moderate the action of the bromine upon the hydrocarbon, the latter was diluted with about twice its bulk of chloroform. 30 C.C. of terpene and 60 C.C. of chloroform were mixed, and the liquid cooled t o - 10" before the bromine (rather less thac 28 grams) was gradually added. The resulting nearly colourless liquid was distilled, the chlo- roform being collected separately, and the distillation carried on till the thermometer went up to 240", and only a few drops of black liquid remained. Much hydrobromic acid was evolved throughout the opera- tion.The liquid was returned to the flask and redistilled five or six Its specific gravity was 0.86529 at 15".82 TILDEN ON THE HYDROCARBONS OBTAINED FROM times till the fuming ceased. It was then distilled several times from sodium. About 14+ grams were collected, corresponding to 56; per cent. by weight of the mixed hydrocarbons taken. The cymene was in both these experiments recognised by smell, optical inactivity, boiling point, and oxidation products. In order to represent the amount of cymene produced by the splitting np of the dibromide, the quantity which was obtained in the first ex- periment, and represents pre-existent cymene, must be subtracted from the quantity obtained in the second: that is, 56+--i* = 49 per cent., OP nearly half its weight.I have not succeeded in obtaining from the liquid, which I believe to be the nearly pure terpene, any solid hydrochloride by the action of hydrochloric acid gas upon the hydrocarbon alone, or upon its solution in ether. Nitrosyl chloride gas passed into the hydrocarbon, whether pure or diluted with chloroform or with alcohol, produces no crystalline nitro- sochloride as in the case of all other terpenes hitherto examined. After passing the gas into a mixture of the terpene with chloroform and allowing the solution to evaporate spontaneously, a few scaly crystals were deposited. These, when collected and dried by pressure, were found to be very easily soluble in rectified spirit, and the solution when set aside deposited nothing but oily drops.4. The presence of cymene in the Russian oil has been already proved. 5 . The oil contains small quantities of viscid hydrocarbons boiling at high temperatures. Within the past few months an examination of Swedish turpentine oil has been published by A. A t t e r b e r g (Dezk Chem. Ges. Ber., X, The one boils a t 156*5-157*5", and has the specific rotatory power + 36.3". The other is said to boil a t 173" to 175", with a specific rotatory power = + 1 9 * 5 O , and a specific gravity ~8612 at 16". The latter is called by A t t e r b e r g '' sglves- trene." I believe it to be identical with the terpene I have described, partly on account of their close agreement in boiling point and rota- tory powers, partly because tthey are almost certainly derived from the same source.I have not, however, been able to obtain a crystallised dihydrochloride in the manner described by A t t e r b e r g. 1202). He finds in this oil two terpenes. 11. Oleurn foliorum Pimi sylvestris. Under this name an oil is prepared for use in medicine by dis- I believe it to be tilling the leaves of the Scotch fir with water. identical with the " Fir-wool oil " imported from Germany.1WE PIKUS SYLVESTRIS, ETC. 83 The specific gravity of the sample I examined was 0.8756, and 100 mm. of the liquid turn the plane of polarisation 5i0 to the right. When distilled it began to boil at 80", owing, as I afterwards found, to the presence of a small quantity of alcohol. The temperature went up rapidly to near 165", below which point about one-fourth of the whole passed over.Between 165" and 175" a distillate was obtained equal to about two-thirds of the original liquid. By careful fractionation this oil was found to contain, beside small quantities of other bodies, two terpenes corresponding in boiling point with those obtained from Russian turpentine oil. The first smells like common turpentine, boils at 156" to 159", and a column of the liquid 100 mm. long rotates the plane of polarisation -k 18' 48'. It is, therefore, like australene dextrorotatory, but more strongly so than the usual variety. It possesses, however, the same chemical constitution, for it behaves with nitrosyl chloride in precisely the same manner. The second terpene, which constitutes about two-thirds the bulk of the oil, boils at 171" or it little above.It is laworotatory. The rotation per 100 mm. is about - 4", but this number can be considered only as an approximation, since the liquid with which the determination was made was undoubtedly contaminated with traces of cymene, as well as of another compound present in the oil, and it was found impossible to purify it completely. This hydrocarbon possesses the sameodour and behaves in the same manner towards reagents as the liquid boiling at the same tempera- ture obtained from Russian turpentine. It also has the same specific gravity at 15", viz., *86529. No solid hydrochloride could be prepared by saturating with hydro- chloric acid gas and exposing the resulting liquid to spontaneous evaporation, or to a very low temperature in a freezing mixture.In addition to these two terpenes, the essential oil of the Pinm syZvestris contains a small quantity of cymene and of pleasant-smelling liquids of higher boiling point. 111. Remarlcs o n the Constitution of the Terpenes. In discussing this question, several facts must be taken into con- sideration : 1. From experiments carried out in conjunction with Mr. Shen- stone (J. Chem. Soc., 1877, i, 554), I find that the number of isomeric terpenes is certainly very small, and according to my belief, there are amongst the natural terpenes only three isomerides essentially dif - ferent in chemical constitution. The known varieties of these differ84 TILDEN ON THE HYDROCARBONS OBTAINED FROM only i x i odour, in action on polarised light and other optical properties,* arid these differences can be fully accounted for without assuming any but mechanical differences of constitution.Thus I find that the terpenes from the following sources yield the same nitroso-derivatives. The terpenes thcmselves boil a t 156" to 159", and have nearly the same density, viz., about 0.860. Dextro-rotatorg. .... Russian turpentine oil ...... Natural order. Conifera?. American turpentine oil.. Oil of leaf of Pinus sylvestyis.. Lmvorotatory. French turpentine oil .......... N.O. Coniferae. Oil of sage .................. N.O. Labiatae. Oil of juniper ................ N.O. Coniferae. To these I feel pretty confident may be added the non-rotating hydrocarbon, terebene, which boils at 155-156", and has the specific gravity 0.860 at 20" (Riban).Like terebenthene, it yields a crystal- line monohydrochloride. The sem i-hy drochlor ide which this substance was supposed to form, has been shown by Riban to be a solution of the monohydrochloride in cymene. To the presence of cymene may also probably be ascribed my failure to obtain a crystalline nitroso- compound from the terebene upon which I operated. The second group of terpenes comprises those which boil a t or near t o 174", and which have a density somewhat below -85 at 20". These all yield the same nitroso-substitution compounds having the same melting point and crystalline form. They are obtained from the fol- lowing volatile oils :- Dextrorotatory . l, Natural Order Oil of sweet orange peel Oil of lemon .............. Oil of bergamot ............ 1 Aurantiaceae.Oil of caraway ............ N. 0. Umbelliferae. The third class comprises the two terpenes of higher boiling point described in this paper as derived from Russian turpentine ........ }N. 0. Conifer@. Oil of leaf of P. syZuest& . z . . * The slight differences observed in density and boiling point in the several members of the same group of terpenes are probably i? the main owing to the fact that in very few cases have the substances operated upon been in a pure state.THE PINUS SYLVESTRIS, ETC. 85 With the former of these, as already stated, Atterberg’s “syl- vestrene ” will, I believe, be identified. They all boil at 171-175”, and have zt specific gravity higher (-865 at 15”) than that of any of the others, whilst they yield no crystalline monohydrochloride or nitroso- chloride.2. All known terpenes yield, by the action of bromine, one and the same cymene, and that a-cymene, the constitution of which is admitted to be that of methyl-propyl- benzene, probably containing iso-propyl. 3. Terpenes are almost entirely broken up by oxidation into carbonic and acetic acids, and yield neither toluic nor terephthalic acid when pure. In those cases in which minute quantities of these acids have been obtained, their production is to be attributed to the presence of traces of cymene in the terpene operated upon. This has been already pointed out by Dr. C. R. A. W r i g h t , and I agree with him upon this point. The production of toluic and terephthalic acids by oxidation of terpin (Hempel, Liebig’s AnnaZen, clxxx, 71) seems to me to throw no light upon the question.I shall refer to this again presently. Terebic and terpenylic acids, from what is known of them, are not benzene derivatives. And, lastIy, it must not be forgotten that con- siderable quantities of oxalic acid are always produced when turpen- tine is oxidised by nitric acid. 4. Cymene cannot be made to combine with hydrogen, so as to pro- duce a terpene. 5. Terebene has been obtained from diamylene by removal of four atoms of hydrogen. Von Richter’s formula for diamylene is repre- sented as follows :- (C,H,) H H CHS H H, I I I I I I I H-C-C-C-C-C=C I I I I H H H H + u It was the consideration of this last fact which chiefly led me to observe that 0 p p e n h e i m’s formula for turpentine, which is identical with the formula for terebene proposed by v.Richter, is not the only nor even the most probable formula which presents itself for these bodies. That formula represenh turpentine as containing the benzene ring of six carbon atoms, as being in fact cymene with two atoms of hydrogen added. Hz l3 H, C-C ,c<c - c>c-cH3 CSH, H-H ThiR formula agrees with my hypothesis that there exist but three VOL. XXXIJI. H86 TILDEN ON THE HYDROCARBONS OBTAINED FROM isomeric terpenes, assuming that the propyl group is always the same. It also agrees with the fact that cpiene can be obtained from tur- pentine by the removal of two units of hydrogen and two of bromine from the dibromide. But it is very difficult t o reconcile with the fact that the same cymene is obtained from all the known terpenes, the isomerism of which must be explained, according to this hypothesis, by the assumption that the hydrogen symbols change their position in the formula. It is also difficult t o explain by this formula why, as I maintain, toluic and terephthalic acids are not obtained by the action of oxidising agents upon the terpenes.The formula which I propose for discussion is derived very simply from the formula for diamylene; for on removing the two pairs of hydrogen symbols, bracketed together in the formula written above, we come to the following expression :- Terpefie a. C,H, H H CH, H H H-C==C-CC---C-CC----C-H I I I I I I It is now clear that this admits of two other modifications, as repre- sented below, viz. :- Terpene p.H C3H7 H H CH3 H H-C=C-Cv-C - C-C-H I I I I I I Teiperze 'y. H H C3H7 H H CH, I I I I I I H-C---C-C=C-C---C-H The isomerism arises, therefore, from the varying posit'ions of the propyl and methyl groups upon this chain of carbon. So long as these two radicles maintain their distance from one another in the formula, the remora1 of one hydrogen symbol from each end of the chain and the linking of the terminal carbons together, result in a formula which is always the same, and which agrees with the received formula for ordinary cymene. The following diagrams represent the most probable expressions for the dibromides of the respective ter- penes, and their conversion into cymene by loss of 2HBr. From a-Terpene. CaH, H H CH, H H I J I I I I Dibromide C-C-C-C-C-C I H A.I H Br BrTHE Cymene Dibromide Cymene D i bromide Cymene PINUS SYLVESTRIS, ETC. C3H7 H H CH3 H H I I I I I I c..c-c=c-c=c From (3-Terpene. H C3H7 H H CH3 H I I I I I I c - c - c ~ c - c ~ c /\ I B Br Br I H H C3H7 H H CH3 H I I I I I I c ~ c - c ~ , c - - - c ~ , c I I From q-Terpene. H H C3H7 H H CH3 c=c-c=c-c-c I I I I I I I H I /\ Br Br H 87 These three formula for cymene are evidently identical. Hempel has found that terpin hydrate yields, when oxidised, toluic and terephthalic acids, and hence concludes that the production of these acids by oxidation of ordinary turpentine cmnot be wholly attributed to the existence of cymene or other impurities in the turpentine. Now when terpin hydrate is heated with diluted nitric acid, the first effect i6 the removal of the elements of water and production of terpinol, which, if it really has the formula usually assigned to it, namely, C,H,,O, or (&HS3(OH), is a condensation product.Since it con- tains but one oxygen-atom, and that supposed to be in the form of hydroxyl, it must evidently be generated by the union of carbon to carbon in some way at present unknown. On the other hand, there is the not improbable suggestion put forward by Gerhardt, that ter- pinol may be a hydrocarbon, an isoterpene. This supposition derives support from the fact, that the terebene semi-hydrochloride, C,H3,C1, to which terpinol was supposed to correspond, does not exist. Whatever be the real nature of terpinol, my object in referring to it is only t o point out that the products of its oxidation must not be assumed without further evidence to be the same as those of a ter- pene.88 TILDEN OX THE HYDROCARBONS, ETC.I have only further to say, with regard to this question, that the formulz proposed in this paper for the terpenes are brought forward with the utmost diffidence. But although I do not insist upon them, it seems to me that, in view of the dead-lock a t which we have arrived in regard to the question of the constitution of these compounds, the time has come when we may fairly test the capacities of some hypo- thesis different from that which has hitherto chiefly found favour. From the terpenes to camphor is a comparatively short step; and although I have no experiments of my own to offer, I cannot forbear a few words upon the subject.The following facts seem to have been established :- 1. Camphor, identical with ordinary camphor in all but rotatory power, has been obtained by Riban by oxidising the lsvogyrate cam- phene from Brench turpentine oil. Camphor is also said to have been formed by oxidising turpentine by permanganate (B e r t h elo t). 2. Camphor, by losing the elements of water, yields ordinary cymene identical with that obtained from the terpenes. These two circumstances seem to connect camphor with turpentine, and at first sight it would appear that the grouping of the carbon symbols must be the same in the formulz of the two compounds. But although I have represented the terpenes as consisting of an open chain of carbon, I feel disposed to consider camphor as a benzene or cymene derivative, and chiefly for the following reasons :- 3. Camphor yields substitution-derivatives with comparative ease. Thus the following compounds have been obtained :- Bromo-camphor, ClOHI5BrO. Chloro-camphor, CloH15CI0. Nitro- camphor, CloH,, ( NOz) 4 0 . 4. Sodium camphor, treated with carbonic anhydride, yields the sodium salt of camphocarbonic acid, a compound which is easily re- solved again into GO, and camphor. This reaction is parallel to the production of salicylic acid from phenol. CloH1,O + C02 = CioH,5O.COOH CsH,O + C02 = C,H,O.COOH 5. By the action of nitric acid, camphor yields, amongst other pro- ducts, a large quantity (more than half its weight) of camphoric acid, which contains as many C and H atoms as camphor. 6. By loss of H,, camphor is converted into carvacrol. These last characteristics, it may be observed, are unlike those of ketones in general, a class of compounds to which camphor, on account of its relations to borneol, is very commonly referred.

ISSN:0368-1645    

DOI:10.1039/CT8783300080

出版商:RSC    

年代:1878

数据来源: RSC

摘要:

89 XIII.-Oi% the Luminosity of Bewzol when twrnt with noidurninow Cornbustib le Gases. By E. FRANKLAND, F.R.S., and L. THORNE, Jodrell Scholar. As early as the year 1852 it was pointed out by one of us that hydro- gen, carbonic oxide, and marsh-gas practically contribute nothing to the light of coal-gas, and that the only constituents of this gas having any substantial value as light-giving agents are those hydrocarbons which combine with fuming sulphuric acid.* The chief of the lumini- ferous hydrocarbons are benzol, ethylene, propylene, butylene, and acetylene ; but although a knowledge of the intrinsic individual luminosity of these and other similar bodies is of very great importance in connection with the subject of artificial light, no successful attempts have yet been made to determine it.We have therefore endeavoured to supply the necessary data, and the following pages contain t,he results of our experiments upon benzol. They will be followed by a similar series upon each of the other chief illuminating constituents of coal- gas. All our attempts to determine the illuminating power of benzol when burnt alone were futile, on account of the extreme difficulty of obtaining a smokeless flame b r the combustion of the pure hydro- carbon. In our efforts to evercome this difficulty we were most kindly assisted by Mr. A l b e r t S i l b e r , who constructed for us several lamps specially designed to consume this liquid ; nevertheless, as the utmost light obtainable without smoke, even with these lamps, did not exceed that of one candle, we were compelled to abandon the attempt as hope- less, and to confine our experiments to the determination of the luminous effect of benzol vapour when diffused in hydrogen, carbonic oxide, and marsh-gas.The illuminating power of benzol, as thus determined, is probably a more trustworthy guide to the value of this compound in coal-gas than would have been any direct determinations with the liquid alone, had such been possible. Moreover, these experiments with benzol vapour have brought to light some points of considerable interest in connection with the relative fitness for their office of the three non-illuminating ga,ses, or diluents, of coal-gas. The determinations were made in the following manner :-Each non-illuminating gas to be charged with the vapour of benzol was collected in sufficient quantity in a holder capable of containing 20 cubic feet, and to which a pressure of 8 feet of water from a ball- * Memoirs of the Manchester Literary and Philosophical Society (2nd Series), vol.x, p. 71. VOL. XXXlII. I90 FRANKLAND AND THORKE ON THE cock cistern could be conveniently applied. From this holder the gas was led through a &-inch tube to a photometric room, where it was received in a floating bell-gasholder of 1 cubic foot capacity, which served to reduce the pressure of the gas delivered from the large holder, so as to bring it within the cont'rol of an experimental gcjvernor, whence it passed to a test-met,er of the usual construction, showing the hourly consumption of gas by observations of one minute's duration. On leaving the meter the gas entered a benzolizer consisting of a brass cylinder 6% inches long, and 3 inches internal diameter, filled with sponge saturated with pure benzol, and so arranged as to compel the whole of the gas to pass through the sponge.The benzolizer was entirely immersed in a large vessel of water, the temperature of which was maintained constant during the con tinuance of the experiments. Each determination of luminosity was the mean of at least ten separate observations. At the close of the photometric readings, and whilst the current of benzolized gas was maintained, a sample was collected for eudiometric determination of the percentage of benzol vapour, which was effected by fuming sulphuric acid in the usual manner .* A.Beizzolized Hydrogem. The hydrogen was prepared from commercial zinc and dilute sul- phuric acid, and contained the usual traces ofimpurities. It is almost needless to say that a flame of it, burning a t the rate of 5 cubic feet per bouy, possessed no measurable amount of illuminating power. After pwsage ihrough the benzolizer, the gas was burnt froin a fish-tail Iiurner, when the following photometric results were obtained :- Bate at which hydrogen passed through meter, 4.95 cubic feet per hour. Temperature of water in which beiizolizer was immersed.. .. Temperature of room. ......... Barometer .................. 29.6 inches. Luminosity corrected to 120 grs. sperm, and 5 cubic feet hydro- gen per hour .............. Ditto, and t o 30 inches barometric 14.8" C .(58-6" F.). 16.0" C. (60.8" F.). 28.13 candles. pressure and 60" F. ........ 28-58 ,, Percentage of benzol vapour in gas 7%; or 100 vols. of hydrogen passing meter, took up 8.22 vols. of benzol vapour. * We find that ordinary sulphuric acid (S02H02), absorbs benzol-vapour rather rapidly, and may be used for its eudiometric determination.LUMINOSITY OF BENZOL, ETC. '31 B. Benzolized Carbonic Ozide. The carbonic oxide was prepared by heating a mixture of potassic ferrocyanide and concentrated sulphuric acid, and was freed from traces of carbonic anhydride by passage through concentrated solution of caustic soda. The gas was then manipulated in the manner just described for hydrogen. It was, however, found impossible t o burn carbonic oxide from a fish-tail burner, under suitable conditions, at R greater rate than 4.22 cubic feet per hour.The following results were obtained :- Rate at which carbonic oxide passed through meter 4.22 cubic feet per hour. Temperature of water in which Temperature of room .......... Barometer .................. 28.88 inches. Luminosity corrected to 120 grs. sperm, and 5 cubic feet of car- bonic oxide per hour ...... 22.66 candles. Ditto, and to 30 inchcs barometric benzolizer was immersed ... 13.0' C. (55.4" F.). 15.0" C. (59.0" F.) . pressure and 60" F. ........ 23.48 ,, Percentage of benzol vapour in gas 6.0, or 100 vols. of carbonic oxide took up 6.38 vols. benzol vapour. C . Bemolixed Marsh-gas. The marsh-gas used in these experiments was made by heating a mixture of sodic-acetate and soda-lime in an iron mercury bottle.So prepared it was far from pure. as the following results of its analysis show ; but we were unable, by this process conducted upon a sufficiently large scale, t o obtain a purer product, and we shrank from the labour necessary t o prepare so large a quantity of pure marsh-gas from zinc-methyl. Indeed had we resorted to this latter method the diffusion of atmospheric air into the pure gas could scarcely have been prevented. Composition of the crude Marsh-gas used in the experimeizts. Marsh-gas .................. 70.08 Hydrogen.. .................. 20.60 C,H,,. ....................... -55 Nitrogen .................... 8.1 7 Oxygen,. .................... -60 100-00 7- 1 292 FRANKLAND AND THORNE ON THE Burnt a t the rate of 5 cubic feet per hour this gas gave the light of 1.4 standard candle.After passing t,hrough the benzolizer it was found impossible to consume the gas from a fish-tail burner, under suitable conditions for the development of light, a t a greater rate than 2.96 cubic feet per hour. The following numbers were recorded in two series of observations :- Hate a t which marsh-gas passed through meter . Temperature of water in which benzolizer was immersed. ........... Barometer ............ Imminosity corrected to 120 grains sperm, and 5 cubic feet marsh-gas Ditto, and to 30 inches Ditto, after deducting 1.4 candle for luminosity of C,H,, in marsh-gas Percentage of benzol- 100 vols. of marsh-gas took up of benzol-va- pour ................ Temperature of room.... per hour ............ bar. press. and 60" F.. . vapour in gas.. ...... I. 11. 9-96 cub. ft. per hour 2.85 cub. f t . per hr. 13.0" C. (55.4" F.) 25.0" C. (77.0" F.) 30.2 inches 29.75 candles 30.56 ,, 29.16 ,, 6.1 6.49 12.0" C. (53%" F.) 22.0" C. (71.6" F.) 30.4 inches 22.92 candles 23.10 ,, 21.70 y , 4-44 4.66 The results of the foregoing experiments may be thus sum- niarised :- 5 cubic feet of hydrogen after benzolization a t 14.8" C., gave for one hour the light of 5 cubic feet of carbonic oxide after benzo- lization, a t 13.0" C., gave for one hour the light of ........................ 23.48 ,, 5 cubic feet of marsh-gas after benzolization at 134", gave for one hour the light of 5 cubic feet of marsh-gas, after benzolization at 12'0" C., gave for one hour the light of ............................21.70 ,, But the volumes of benzol vapour taken up by 100 vols. of the three gases a t the different temperatures jush specified were :- 28.58 candles. 29.16 ,,LUhIINOSITY OF BEKZOL, ETC. 93 For hydrogen . . . . . , . . . . . , . , 8.22 vols. a t 14.8" C. ,, carbonic oxide . . . . . . . , . . 6.38 ,, 13*O0 C. ,, marsh-gas (1st experiment) 6.49 ,, 13.0" C. 5 , ,, (2nd ,, ) 4-66 ,, 12.0" C. Otherwise expressed it may be stated that, measured at 60' F. and 30 inches barometric pressure- ,410 cubic foot of benzol rapour buimt with H gave for one hour the light . . . . . . . . -320 cubic foot of benzol vapour burnt with GO gave for one hour the light of . . . . -3154 cubic foot of benzol vapour burnt with CH4 gave for one hour the light o f .. . . .231 cubic foot of benzol vapour burnt with CH, gave for one hour the light of . . . . 1 cubic foot of benzol vapour burnt with H gave for one hour the light of . , . , . . . . 1 cubic foot of benzol vapour burnt with CO gave for one hour the light of . . . . . . . . 1 cubit foot of benzol rapour burnt with CH, gave €or one hour the light of . . . . . . . 1 cubic foot of benzol vapour burnt with CH4 gave for one hour the light of . . . . . ,. . 28.58 candles. 23.48 29.16 21.70 .. ,, ,, Hence at the standard temperature and pressure- 69-71 candles. 73.38 92.45 93.94 > 7 \, ,, Or if N cubic feet of benzol vapour burnt with H give for one hour the n cubic feet of benzol vapour burnt with CO will give for one hour 1% cubic feet of benzol vapour burnt with CH, will give for one hour TL cubic feet of benzol vapour burnt with CH, will give for one hour light of 1 candle, then the light of 1.053 candle ; the light of 1.326 candle ; the light of 1,347 candle.Now 1 cubic foot of benzol vapour a t 60" F. and 30 in. bar. press. weighs 1,444 grains, and therefore 1 lb. (7,000 grains) of benzol burnt with hydrogen gives a light equal t o that of 337.9 sperm candles for one hour, or 5,793 lbs. of spermaceti. Hence 1 lb. aroirdupois of benzol gives when burnt with- H the light yielded by 5.793 lbs. of spermaceti. CO ,, ,, 6.100 9 , ,? CH4 > 1 9 , 7.682 ,, 7 , CH4 ,> > > 7.803 ,> 7 )94 FRASELAND AND THORNE ON THE LUMINOSITY OF BENZOL. The light evolved by the luminiferous constituents of coal gas is therefore not altogether independent of the proportion of the diluents (hydrogen, carbonic oxide, and marsh-gas) with which they are mixed; for the foregoing experiments show that a given weight of benzol produces 5.3 per cent, more light when it is diluted with car- bonic oxide than when it is diffused in hydrogen, and between 32% and 34.7 per cent.more in marsh-gas than in hydrogen, and tlie last numbers would doubtless have been still higher had the marsh-gas been pure. This difference in the luminosity of benzol when burnt in different media is probably due, in part at least, to tlie different pyrometric t Iiermal effects of the three gaseous media employed. The actual pyrornetric effects of hydrogen, carbonic oxide, and marsh-gas when burnt in atmospheric air have never been determined, but calculated from their absolute thermal effects as measured by F a v r e and Silbermann, the temperatures of their flames would be- Hydrogen.................. 2,080" C. Carbonic oxide ............ 2,828" Marsh-gas ................ 1,935" The actunZ pyrometric effects of hydrogen and marsh-gas are pro- bably nearly equal, whilst that of carbonic oxide is considerably higher. H e r t helot, however, estimates the average pyrometric effect of car- bonic oxide burnt in air (1,975' C:) to be only 75" C. higher than that of hydrogen (1,900" C.). If the actual pyrometric effects of the three gases bear the same relation to each other as the calculated values, the greater amouut of light emitted by benzol when burnt with car- bonic oxide, receives a satisfactory explanation, but the still higher illuminating effect obtained by burning the benzol in marsh-gas is not accounted for. It has been shown by one of us (JozwnuZ of Gus Light- k q , 1867) that marsh-gas burns with a flame of' considerable luminosity when it is heated to about 300' C. along with the air necessarg for its combustion, and it is certain that the pyrometric effect of marsh-gas would be augmented by the presence of 5 cr 6 per cent. of benzol vapour, but whether this is the sole cause of the increased light must be determined by further investigation.

ISSN:0368-1645    

DOI:10.1039/CT8783300089

出版商:RSC    

年代:1878

数据来源: RSC

摘要:

95 X1V.-Action of Reducing Agents on Potassium Permanganate. By FRANCIS JONES, F.R.S.E. h a paper on Stibine (this JozcrnaZ, xxix, 642), read before this Society last year, I mentioned incidentally that this gas and its analogues decompose solution of potassium permanganate with sep: - ration of oxide of manganese. I also pointed out that the precipitate consisted only of oxide of manganese, and that the antimony, arsenic, &c., passed into solution." I have since examined these reactions more fully, as well as the action of hydrogen itself, which has long been known to act on permanganates (Gmelin's Han,dboolc, iv, 211). Tl-e results show that hydrogen, ammonia, phosphine, arsine, and stibine all decompose permanganates with separation of hydrated sesquioxide of manganese, and formation of salts of phosphorus, arsenic, &c.The experiments were made by passing the purified gases into a moderately strong solution of potassium permanganate until the dis- appearance of the purple colour. The precipitate was then allowed to settle, washed by decantation, and dried over sulphuric acid or on the water-bath. The liquid was poured off, filtered, and examined qualita- tively. The oxides were analysed in various ways, but generally by reduction in hydrogen to protoxide, or by ignition in air to manga- noso-manganic oxide. Occasionally the combined water was also estimated as a check. I. Action of Hydrogen. (a.) In Neutral Solutions.-When hydrogen is passed through a neutral solution of potassium permanganate, a light brown precipitate soon separates, but settles very slowly.After the prolonged action of the gas the precipitate becomes denser, and the superuatant liquid becomes perfectly clear and colourless. This clear liquid is alkaline to test-paper, and contains only potash ; the precipitate is hydrated sesqni- oxide of manganese. 2KMnOl + BH = Mn,O, + 2KH0 + 3H20. Tlie reaction may be thus represented :- Analysis of Oxide. A. 0.4465 gram 0.3658 gram = 63.44 6'2.50 (Mn203 + H,O) * E. S c h o h i g has since proposed this reaction as a means of purifying hydrogen from these gases, a method which I had likewise adopted with excellent results. J. pr. Chenz. [ 2 ] , xir, 289. Substance. MnO. Per cent. Mn. Calculated.96 JONES ON THE ACTION OF REDUCING AGENTS The absorption of hydrogen by solution of permanganate is tolerably rapid, and increases with the temperature and with the surface of liquid exposed t o the action of the gas.It may be shown experi- mentally, by filling a wide test-tube with hydrogen, and placing it mouth downwards in a solution of permanganate ; the solution will steadily rise in the tube until all the hydrogen has been oxidised. Or, if a tube filled with hydrogen and containing a few drops of a satu- rated solution of permanganate be sealed up and shaken from time to time, the whole of the hydrogen will be oxidised in two or three days, so that, if the end be broken off under water, the liquid will rise to the top of the tnbe. A similar result may be obtained in half-an-hour by placing the sealed-up tube for that length of time in a water- bath.(b.) In Acid Solutions.-The permanganate was acidified with a few drops of pure dilute sulphuric acid, and the hydrogen passed through. A precipitate soon separated, darker in colour than in the neutral soh- tion, and very dense. It consisted of manganese sesquioxide ; the fil- trate contained only potassium sulphate. Analyses of Oxide. Substance. MnO = per cent. manganese. Calculated. C. 0.4318 ,, 0.3408 ,, = 61.14 62.50 Mnz03 + H?O B. 1.8040 gram 1.455 gram = 62.50 62.50 D. 0.6220 ,, 0.5395X ,, = 62.49 62.50 (c.) In. Alkaline Solutions.-Pure caustic soda was added to the per- manganate ; the hydrogen acted much more slowly than in the pre- vious cases ; the liquid first became green, by reduction to manganate, and this colour disappeared only after the prolonged action of the gas.The precipitate was pale brown, and very similar in appearance to that produced in neutral solutions. 1 AnaZyyses of Oxide. Substance. MnO = per cent. manganese. Calculated. E. 0.5415 gram 0.4410 gram = 63.08 62.50 ‘1 Mnzos + H,o F. 0.5940 ,, 0.4850 ,, = 63.24 62-50 11. Action of Ammonia. The action of ammonia on potassium permanganate has been examined by several chemists. It is stated to precipitate hydrated peroxide of manganese and t o evolve nitrogen (Grnelin’s Handbook, iv, 237). Wohler (Jahresbericht, 1865, p. 150) found that nitrous acid was also produced in quantity. * Weighed as Mn304.ON POTASSIUM PERMANGANATE. 97 On adding a strong solution of ammonia to one of permanganate, the mixture becomes hot, nitrogen is slowly evolved, and a brown flocculent precipitate of manganese sesquioxide separates out.The filtrate contained potassium nitrite and nitrate. The reaction may be represented by the following equation :- 8RMnOa + 8NH3 = 4&tn203 + KNO, i KNOz + GKHO + 9HZO + 6N. Analysis of Oxide. Water. Substance. MnO Calculated. Found. Calculated. G. 1.0613 gram 0.1508 = 62.09 62.50 10.71 10.22 111. Action of Phosphine. Phosphine, prepared by warming phosphorus with solution of pot- ash, was passed through a series of flasks containing solution of potas- sium permanganate (the air had been previously expelled from the apparatus by a current of hydrogen). The escaping gas was not spontaneously inflammable so long as any pernianganate remained un- decomposed ; the completion of the readion was therefore easily noted by the gas regaining this property at the exit-tube of the apparatus. The excess of phosphine was expelled by hydrogen, and the precipi- tate collected and analysed.One portion of the oxide dried over sulphuric acid was found to contain a molecule more of water than the other portion, which was dried on the water-bath, but in each case the oxide obtained was the sesquioxide. The filtrate was quite clear and colourless, and had a slightly alka- line reaction. It gave the reactions both of phosphorous and phospho- ric acids. 6KMn04 + 4PH3 = 3Mn2O3 + 21C2HP03 + 2KH2P03 + 3H20 and 2KMnOa + PH3 = Mn,O, + KzHP04 + H,O. These changes may be thus represented :- Analyses of Oxide. H. 0.7804 gram 0.5674 gram = 56-31 56.70 (31n203 + 2H20) I.0.7995 ,, 0.6328 ,, = 61-31 62.50 (Mn,O, + HzO) Substance. MnO = per cent. of manganese. Calculated. IV. Action of Arsine. Arsine, prepared by allowing R solution of arsenic in hydrochloric acid to drop on granulated zinc, and purified by passing the gas through a dilute solution of soda, was passed into a neutral solution of potassium permanganate. The colour of this solution rapidly disap- peared, and a dark brown precipitate, which contained a trace of arsenic, separated out. The precipitate was found on analysis to be98 JONES ON THE ACTION OF REDUCING AGENTS manganese sesquioxide ; the filtrate, which was faintly alkaline, con- tained only potassium arsenate. The reaction may be thus repre- sented* :- 2KMn04 + ASH~ = Mn203 + K,HAsO4 + H20.Analyses of Oxide. J. 0.8250 gram 0,6135 grain = 57-60 56.70 (Mn203 + 2H,O) Substance. MnO = per cent. manganese. Calculated. K. 1.0200 ,, 0.8325 ,, = 63.19 62.50 (M11203 + H,O) V. Action of Stibine. This gas, prepared similarly to arsine, behaved like that gas, except that the precipitate was more flocculent ; the filtrate contained potas- sium antimonate and a small trace of manganese. The reaction may be thus represented- 2KRlnOi + SbH, = MU203 + KZHSbOa + HZO. Analyses. Substance. MnO. Per cent. Mn. Calc. Found. Calc. L. 0.9100 0.7465 = 63.53 62.50 9.81 10.22 M. 0.8895 0.7075 = 61.61 62.50 - -- So far then, the results show that ammonia and its analogues react on potassium permanganate in a closely similar manner, and that hydrogen agrees with them in so far as the nature of the precipitated oxide is concerned ; it ir, uniformly the hydrated sesyuioxide.On ex- tending the investigation to the action of other reducing agents on potassium permanganate, I obtained as before precipitation of the sesquioxide, but accompanied (in all the cases I have examined) by the Zibeyatio?a of oxygen. Water. I now give time results. VI. Actio$L of Oxulic Acid. The action of oxalic acid on permanganates has been made the sub- ject of investigation by many chemists. €3 e r t h e lo t (Juhresbem'cht, 1867, page 334) found that it is oxidised to carbon dioxide and water, not only in acid, but also (though slowly) in alkaline solutions. Ver- non H a r c o n r t (this Jouurttul [el, v, page 460) in a paper on the * S c h o b i g (Zoc.cit.) represents this reactiou by the following equation, but gives 10H385 + 16KMn04 = 5K34s04 + KRTnAsO4 + 2Mn3(As04)a + 9Mn(OH)2 The reaction has also been studied recently by P a r sons (ChmicaE News, 1877, page 236), who represents it by the following equation :- 3K2&h208 + ~ A S H ~ = 3Mn202(0H):: + 2As203 + 6KH0. no proof of the formation of the various products formulated- + 6Hz0.ON POTASSICW PERMANG ANATE. 9 9 action of oxalic acid on permanganate, gives the following equation for the reaction- 21(Mn04 + 3HzSOa + 5HzCz@4 = KzSOa + 2MnS04 + loco2 + 8HZO. I find, however, that this equation does not express all that occurs: since oxygen is evolved along with the carbon dioxide, both when sul- phuric acid is present and when it is absent. On adding solution of potassium permanganate to a warm solution of oxalic acid, the purple colour of the former rapidly disappears ; the liquid remaining colourless up to a cert.ain point, when oxalate of man- ganese separates out even in the warm liquid.Beyond this point, the further addition of permanganate produces a brownish coloration, and then precipitation of oxide of manganese, which continues until the whole of the oxalate has been decomposed. The reaction of the liquid, acid a t first, changes to neutral, and finally to alkaline. Carbon dioxide is evolved from the beginning to the end of the oxidation, and along with it oxygen. These two stages in the reaction may be represented by the follow- ing equations :- (a.) 2KAl'n04 + 8C2H204 = 2MnC204 + K2C2Oa + loco2 + 8H20, (b.) 2MnC204 + 2K1Sln04 = 2Mn203 + KZC03 + 3c02 + 0.The presence of oxygen in the evolved gases was ascertained by ex- periments made in one or other of the following ways :- (1.) Solutions of oxalic acid and potassium permanganate were separately poured into a long glass tube which was completely filled, then closed with the thumb, inverted and opened under water con- tained in a small beaker. The liquids soon mixed by diffusion and bubbles of gas rose to the top of the tube. When no more gas was evolved, the quantity obtained was decanted into another tube, shaken up with caustic soda to remove the carbon dioxide, and the residual gas tested for oxygen in the usual way. (2.) A flask was closed with an india-rubber stopper through which passed three glass tubes ; one of these reached to the bottom of the flask, and was connected with an apparatus evolving carbon dioxide, another conveyed the evo1-i-ed gases to a glass gas holder, and the third was wide enough to admit the point of a stoppered burette which was fitted air-tight into the tube.The flask contained the liquid to be examined (e.y., oxalic acid solution or oxalic mixed with dilute sul- phuric acid), the burette contained the permanganate. With this apparatus an experiment was made by first expelling the air with a current of carbon dioxide which was stopped as soon as the air was expelled. The permanganate was then allowed to flow in, and the gases produced by the reaction were received in the glass gas-holder100 JONES ON THE ACTION OF REDUCING AGENTS which contained solution of caustic soda to absorb the carbon dioxide.The unabsorbed gas was collected in a tube and tested for oxygen as before. I intend to make this reaction of oxalic acid on permanganate the sizbject of further investigation, and in the meantime need only say tha't in whatever way I varied the conditions of the experiment, oxygen was uniformly obtained as a product of the reaction; so that, whether there be excess of oxalic acid or of permanganate, whether the solutions be strong or dilute, whether another acid be present or not, in each case oxygen is evolved. It could scarcely be doubted that other reducing agents than oxalic acid might act similarly on permanganate, and liberate oxygen. I therefore examined its action on ferrous salts, and at once perceived that this was the case; oxygen is evolved in presence or absence of acids, in dilute or in strong solutions.Further, a few experiments soon showed me, that in the action of sulphuric acid upon manganese dioxide in presence of an oxalate, oxygen is evolved along with the carbon dioxide. Obviously, these observations are of importance in connection with the analysis of manganese dioxide, and with the use of permanganate in volumetric analysis. VII. Manganese. Chloride. When a strong solution of permanganate is added to one of man- ganese chloride, sesquioxide of manganese separates out and bubbles of gas are evolved. On examining this gas I found it to consist of a mixture of chlorine and oxygen. The reaction may be thus repre- sented- MnClz + RlfnOp = Mn,O, + KC1 + C1 + 0.On mixing dilute solutions of the same salts, oxygen was evolved, I also ascertained that oxygen is evolved when but not chlorine. manganese sulphate is added to solution of potassium permanganate. Analysis of Om&. N. 0.879 gram 0.505 gram = 62.13 62.50 (1\In203 + H,O) It will be notieed in the preceding experiments that the oxide of manganese uniformly precipitated is the sesquioxide, and not the dioxide, which is generally stated to result from the decomposition of permanganates. I f the dioxide be actually precipitated, I think it not improbable that it a t once decomposes into sesquioxide and oxygen (hence the oxygen in the above experiments), behaving in this respect like man- ganese tetrachloride, which is formed when cold hydrochloric acts Substance. MnO = per cent.of manganese. Calculated.ON POTASSIUM PERMANGANATE. 101 upon manganese dioxide, but which soon splits up into the dichloride and free chlorine. And if the dioxide be not obtained by the reduc- tion of permanganates, it seemed doubtful whether it can be obtained at all by precipitation. Some confirmation of this supposition was obtained by an examina- tion of two oxides prepared by methods which are said to yield the hydrated dioxide of manganese, viz., the oxide obtained by the addi- tion of bromine to a mixture of a manganese salt with ammonia, and the oxide obtained in Weldon's process for the recovery of manganese from the chloride. In the former case the oxide contained 62.36 per cent. of manga- nese, in the latter the oxide, after washing with dilute nitric acid to remove lime, &c., was found to contain 62.57 per cent.of manganese. Both these analyses agree closely with the formula, Mn,O, + H20, which requires 62.50 per cent. of manganese. Surnnaary. (u.) Hydrogen decomposes neutral, alkaline and acid solutions of potassium permanganate, with separation of sesquioxide of manganese in each case. (b.) Hydrogen left in contact with solution of permanganates is completely absorbed a t the ordinary temperature, more rapidly at 100" c. ( c . ) Ammonia decomposes potassium permanganate with liberation of nitrogen, separation of manganese sesquioxide, and formation of potassium nitrite and nitrate. (d.) Phosphine precipitates sesquioxide, and potassium phosphite and phosphate are formed. (e.) Arsine precipitates sesquioxide, and potassium arsenate is formed. (f.) Stibine precipitates sesquioxide, and potassium antimonate is formed. (g.) The first action of oxalic acid on potassium permanganate re- sults in the formation of manganese and potassium oxalates, water and carbon dioxide. After this stage has been reached, the further addi- tion of permanganate produces precipitation of manganese sesquioxide, formation of potassium carbonate, and evolution of carbon dioxide and oxygen. (h.) Oxygen is evolved along with carbon dioxide when sulphuric acid acts on manganese dioxide in presence of an oxalate. (i.) Oxygen is evolved when ferrous sulphate, manganese sulphate, or manganese chloride act on potassium permanganate. Oxygen is also evolved in presence of sulphuric acid.

ISSN:0368-1645    

DOI:10.1039/CT8783300095

出版商:RSC    

年代:1878

数据来源: RSC

摘要:

XV.-On the Decomposition-products of Quinine. By W. RAM SAY, Ph.D., Tutorial Assistant of Chemistry, Glasgow University; and J. J. DOBBIE, MA., Clark Scholar in Nab. Sc., Glasgow University. Fhst Paper (Oxidation with Permanganate). CLOEZ and Guignet (Compt. rend., xlvii, 710), by oxidising quinine with permnnganate of potash, obtained nitxate and carbonate of potas- sium and apeculiar acid. With the view of examining this acid and the other products of de- composition of quinine, we repeated their experiment. The oxidation, and subsequent separation of the acid were conducted in the following manner:-5 grams of quinine were treated with 50 grams of permanganate, a t the ordinary temperature, a gentle heat only being applied to start the action. When reduction of the per- manganate mas complete, the alkaline liquid was filtered from the manganese dioxide and neutraIised with nitric acid.On adding nitrate of lead to the hot neutral solution, a curdy white precipitate of the lead salt of the unknown acid was obtained. This salt was decomposed with a current of sulphnretted hydrogen, the liberated acid filtered from the lead sulphide, and evaporated to dryness. On taking up the residue with alcohol, the alcoholic solution deposited on standing a red powdery substance. The free acid, filtered from the red powder, mas thrown down with silver nitrate, and the silver salt treated in the same way as the lead salt with sulphnretted hydrogen. The filtrate from the silver sulphide, on being slowly evaporated over sulphuric acid, gave delicatle needle-like crystals of the free acid.A small portion of the acid thus liberated, on being heated, gave off the smell characteristic of the decomposition by heat of dicarbopy-idenic acid, and afforded strong evidence in favour of the identity of the acid produced from quinine with that which Professor Demar obtained by oxidising picoline with potassium permanganate. The acid from quinine has been obtained in two different forms- &., in plates and in short prisms. As yet we have not succeeded in getting the long hair-like needles, in which dicarbopyridenic acid crystallises when free from water. On heating for several hours a t 100°C., 0.3373 gram of the acid lost 0.0324 gram = 9.6 per cent. C,H,N04.H20 contains 9-83 per cent. H,O. Combustion of 0.1334 gram acid gave 0.338 gram H20, and 0-218 gram CO, = 3-16 per cent.H, and 44.56 per cent. C.RAMSAY AND DOBBIE ON THE DECOMPOSITION, ETC. 103 Dicarbopyridenic acid contains H, 3.00 per cent. ; C, 50.39 per cent. The carbon of the acid obtained from quinine is thus between 5 and 6 per cent. lower than that of dicarbopyridenic acid; but as the quantity burned was very small and apparently not quite pure, the approximation of the results obtained by experiment to the calculated percentage of C and H in dicarbopyridenic acid may, taken together with the facts to be mentioned, render the identity of the acids at least highly probable. A qualitative examination of the acid showed that i t contained nitrogen. Owing to the difficulty of getking entirely rid of the red powder already mentioned-a trace of which always comes down with the salts-it was found impossible to make an exact determination of the melting point.The purest specimen obtained blackened below 200", and melted apparently at 251-2.52". The melting point of dicar- bopyridenic acid is 237.5" ; but this can be observed only when very pure specimens are used. With ferrous sulphate the acid gave the red colour characteristic of dicarbopyridenic acid. The silver salt of the acid comes down in boiling solution as a white curdy precipitate. 0.1425 gram of the salt gave 0.0801 gram Ag = 56.21 per cent. The neutral silver salt of dicarbopyridenic acid con- tains 56-69 per cent. Ag. The silver salt, on heating, behaves like mercury sulphocyanide. The silver salt of dicarbopyridenic acid has the same peculiarity.On titxating the acid with a standard solution of potash, 0.2948 gram acid required for neutralization 0.16!)2 gram K,O = 0.1404 gram K. Calculating this amount of potassium to hydrogen, we obtain 0.00358 gram, as the weight of hydrogen replaced by potassium; therefore, 0.2948 gram less 0.00358 gram, plus 0.1404 gram = 0.43162 - 100 x 0.1404 0.43162 - gram = the amount of potassium salt formed, and 32.50 per cent. The percentage amount of potassium in the neutral potassium salt is therefore 32.50. The corresponding salt of dicarbopyridenic acid contains 32.15 per cent. K. On titrating the acid from the products of another oxidation uTith soda in the same way, 0.0792 gram acid required for neut,ralization 0.0239 gram NazO = 0.0218 gram Na.Calculating this to H as before, we find 0.00895 gram. Therefore, 0.0792 gram, less 0.00095 gram, 0.10015 = plus 0.0218 gram = weight of salt = 0.10015 gram, and 21.76 per cent. The neutral sodium salt of dicarbopyridenic acid contains 21.80 per cent. NR. 100 X 0.0218 Percentage of Na in salt = 21.76.104 RILEY ON THE ESTIMATION OF These results -the analysis of the silver and alkali salts, the analysis of the acid itself and its behaviour on burning, and with ferrous sul- phate-seem to leave but little doubt as to the identity of the acid which we have obtained from quinine with that got in the same way from picoline. Unfortunately the very high price of quinine prevented us in the first instance working with a quantity sufficient to give a yield of the acid large enough for a complete investigation.Having ascertained how the acid may be most economically separated, it was our intention to repeat our experiments on a larger scale; but as the attention of others (Deut. Client. Ges. Ber., 1877, p. 1930) has recently been directed to the same acid, we believe that it is unnecessary to apologize for the immediate publication of our results in their present imperfect form, It has been mentioned, that on dissolving in alcohol the residue obtained by evaporation of the filtrate from the lead salt, the solution, after standing for some time, gave a red deposit. This red substance is probably a product of imperfect oxidation, and seems to be iden- tical with Bl a r c h a n d ' s quinetin, which is obtained by oxidizing quinine with peroxide of lead and sulphuric acid. If the oxidation of quinine with potassium permanganate, instead of being conducted a t the ordinary temperature, is carried on a t 100" C., the quantity of red substance obtained is less, and the yield of acid greater. M. Marchand having kindly furnished us with the details of his method of oxidation with peroxide of lead, we prepared a quantity of quinetin. On subjecting this quinetin to oxidation with perman- ganate, we obtained an acid apparently identical with that got by the direct oxidation of quinine. At present we are engaged in investigahg the nature of March a n d' s quinetin, and in our next paper shall give the results of that investi- gation, together with those of experiments on the action of barium hydrate, and various oxidising agents on quinine and allied alkaloids.

ISSN:0368-1645    

DOI:10.1039/CT8783300102

出版商:RSC    

年代:1878

数据来源: RSC

摘要:

104 RILEY ON THE ESTIMATION OF XVL-On the Estiqnatiorh of Phosphorus in Iron and Steel. By EDWARD RILEY. THE accurate determiriat,ion of the amount of phosphorus present in iron and steel, more especially since the introduction of the Bessemer and Siemens-Martin processes, now so largely used, has become of the greatest technical impor tance. The method most generally employed at iron and steel works isPHOSPHORUS IN IRON AND STEEL. I05 that known as the molybdate method, the other is known as the magnesia method; the latter is not so much used, as the results cannot be obtained so quickly. I need hardly say that in iron and steel works, where so many determinations are required, time is a most impor tan t consideration. It is not my intention, in this communication, to enter into very minute details as to ths method employed in precipitating phosphorus by molybdic acid, or by molybdate of ammonia; as it has been so frequently described in various works, and I find practically that almost every operator varies in the exact method he employs.The percentage of phosphorus is as a rule so small in the pig iron used and the steel made, that to determine it accurately requires much practice and some amount of analytical skill. Speaking from my own experience of more than 25 years, and from my experience and observation as to the results obtained by others who use the molybdate method, I must say that as a practical fact the results obtained by many chemists by it are not satisfactory. I have hesitat,ed to adopt it in my laboratory, although I must admit I have on some occasions obtained very satisfactory resuits ; still I have always felt a certain amount of doubt about the process, whereas witb the magnesia method I have no doubt whatever.I must however admit that grave errors may be made by the magnesia method, and that great care is required in using it. It is quite the exception to find either iron or steel without phos- phorus, only some very few Swedish and foreign irons are free from it. I have, however, very frequently samples and analyses sent to me in which no phosphorus is given, whereas on examining the samples I find in most cases a very appreciable and weighable amount. I am speaking now of analyses made by chemists who have some expe- rience in iron and steel analysis ; by others it is not a t all unfrequent for -10 to -20 per cent.to be overlooked. The cause of this low estimation, or failing to detect the phosphorus, is, I believe, in the case of the molybdate method, due to having the solution too acid, or in other cases not adding a sufficient amount of molybdate solution. In the case of high estimates, which are not unfre- quent, the excess is due to molybd-ic acid being thrown down together with the phosphorus precipitate. The great importance of the accurate determinat'ion of phosphorus, induced me to have a series of experiments made by various operators, so as to ascertain how nearly the practical results obtained in iron and steel works, and in various metallurgical laboratories, actually agreed with the absolute amount of phosphorus present. For this purpose pure peroxide of iron mas prepared, ordinary iron borings were dissolved in dilute sulphuric acid, the solution filtered VOL.XXXIII. K106 RILEY ON THE ESTIMATION OF from the residue, and the sulphate of iron crystallised out ; the mother- liquor was separated and the cryst,als washed with distilled water, re- dissolved in distilled water and recrystallised. The crystals having again been washed, were then dissolved in distilled -water, the solution peroxidised with pure nitric acid, and the peroxide of iron precipi- tated from the diluted solution with ammonia. After washing four times by decantation, the precipitate was redissolved in pure hydro- chloric acid, and reprecipitated by ammonia; the oxide of iron was washed until it was practically free from ammoniacal salts, then detached from the calico filter used, dried and ignited at a dull red heat in a muffle.Before using the peroxide it was thought desirable to ascertain if it was absolutely free from phosphorus. It was tested by the magnesia method usually employed by me. The peroxide of iron was dissolved in strong hydrochloric acid, then reduced, after diluting the solution with sodium sulphite, and the excess of sulphurous acid was expelled by boding ; the solution was nearly neutralised with ammonia, acetate of ammonia added ; the phosphoric acid was then precipitated on boiling with n small amount of peroxide of i'ron, as basic acetate and phosphate. When only minute quantities of phosphorus are present, there is usually enough peroxide of iron in the solnt'ion to precipitate the phosphorus ; if not, a drop or two of a dilute solution of perchloride of iron is added, or a few drops of bromine-water, enough to make the precipitate of a red tinge.The solution after boiling is filtered, the precipitate dissolved in strong hydrochloric acid (it is not necessary to wash the precipitate before dissolving it), and the filter thoroughly washed. The solution of the phosphoric acid with some iron is then evapo- rated to a small bulk, about half an ounce (15 c.c.) ; to this is added about 200 grams of citric acid (13 grms.) ; the solution neutralised with -960 ammonia ; some 20 to 30 drops of magnesia solution added, then a moderate amount of -880 ammonia, so as to make it strongly alka- line.The whole bulk of liquid should not exceed 16 to 2 ounces (50 c.c.). No immediate precipitate is formed unless the phosphorus amounts to -10 or more per cent. ; on standing, however, for R night, the characteristic small star-shaped crystals of the ammonia-mag- nesium phosphate are found adhering to the sides of the beaker and on the stirrer. The solution is strongly agitated the next day with the stirrer, either at once or after the lapse of a little time, whereupon a further precipitate of the granular characteristic ammo- nia phosphate is formed. The solution is allowed to stand for another night, and filtered off on the following day; and the residue is mashed with ammonia-water, dried, ignited, and weighed. The precipitate, after ignition, is either perfectly white or colouredPHOSPHORUS IN IRON AND STEEL.107 only with a little carbon. If any difficulty is experienced in burning this over the gas, it may be heated with a few drops of fuming nitric acid with the cover over the crucible; it then becomes perfectly white. In no case do I find that any iron is precipitated with the magnesia salt. The precautions necessary are to have not too much iron present. I have found that the usual quantity is from 5 to 6 grains of iron from a phosphorus determination on 150 grains of steel. A large excess of citric acid must be used, and also of ammonia. The soh- tions should be of a paleish yellow-green colour ; if it is very dis- tinctly red, good results are not obtained ; if it is dark-red, the results are altogether fallacious.The precipitate obtained by magnesia is so characteristic that there cannot possibly be any mistake about it. The peroxide of iron was found to contain a distinct amount of phosphorus ; 206.595 grains gave Mg2Pz0;*0135 grain. Equal to phosphorus per cent. in the Fe,O,. ........... .0018. 7, 7 7 in iron or steel.. ........ *OQ26. Some pure Mg2Pz0, was prepared by taking about +-pint of mag- nesia solution, made by adding a considerable amount of ammonia and chloride of ammonium to a saturated solution of ordinary sul- phate of magnesia, and filtering off the precipitate and insoluble matter; this solution on standing generally yields a deposit. The clear solution is used for phosphorus determinations. To the above solution, after dilution, was added phosphate of soda, the precipitate formed was allowed to settle, the supernatant liquid decanted off; and the precipitate washed four times with distilled water ; it was then redissolved in hydrochloric acid, reprecipitated with ammonia, filtered, and washed until no appreciable residue was left on evaporating the washings to dryness.The dried precipitate was ignit,ed in a muffle until it. was quite white. In carrying out the experiments, each of my assistants ignited from 213 grams to 218 gramsof the pure peroxide of iron, this quantity re- presenting about 150 grams of metallic iron, the usual quantity taken for phosphorus determinations in steel. The above quantity was dissolved in strong hydrochloric acid. I then very carefully myself weighed out the phosphorus salt, giving each a different quantity.The solution of the peroxide was poured on the magnesium phosphate in a small beaker, and warmed until i t was completely dissolved. The phosphorus waB then determined by my ordinary method, each K 2108 RILEY ON THE ESTIMATION OF assistant working on a solution of iron containing a quantity of phos- phorus unknown to him. The following are the results that were obtained by each :- Peroxide of iron Mg2P,07 Mg,P,O, Mg2P20i taken. added. found. reprecipitated. I. W. H, H e r d s m a n . . 218.62 -46 *475 *460 11. A. E. Tucker ...... 213.45 -48 ,500 -500 111. G. A. J a r v i s ...... 215.26 -35 *380 -365 IV. F. J. Bolt . . . . . . . .214-255 *72 -775 ,745 V. A. L. H u g h e s . . .. 215.215 -71 * 725 - Converting the peroxide of iron into metallic iron, and calculating the percentage of phosphorus present in the iron (after deducting the small amount of phosphorus found in the peroxide), the results are as follows :- Peroxide of iron to Phosphorus p.C. Phosphorus p. c. Difference p. c. in metallic iron. added. found. phosphorus. I. 153.034 -0839 *0840 .0001 11. 149.415 -0897 -0908 -0011 111. 150.682 *0648 -06 78 ,0030 IV. 149.978 -1340 -141 7 -0077 V. 150-6.50 ,1316 *1336 *0020 or a mean error in excess of *0028 per cent. I n all cases the calculation is made on the first precipitation and weighing of the magnesium phosphate. The first four, as my assistants, have had considerable practice in determining phosphorus. No. 5 determination was made by one of my pupils who has had but little practice, not having made more than three or four determinations of phosphorus in iron and steel.The nbo-re were the only experiments made, and it will be seen that practi- cally the exact amount of phosphorus was obtained that I weighed in. In reprecipitating the MgJ'ZO, after weighing, it was dissolved in strong hydrochloric acid, a very small crystal of citric acid added, and excess of ammonia ; and the precipitate after standing for two nights was filtered and weighed as before. An experiment was made on some of the phosphate of magnesia to see what was the actual loss on reprecipitation. Mg,P,O;. Ignited oTer Bunsen burncr. Ignited in muffle, 2.46 gave 2*445* 2.42 The experiment was made with the same bulk of liquid as in an ordinary phosphorus determination, and in precisely the same way, except that no citric acid or magnesia salt was added.* Not quite white.PHOSPHORUS IN IROX AKD STEEL. 10:) I shculd perhaps mention that when there is much phosphorus pre- sent, as in ordinary pig iron (not Bessemer pig), I operate on smaller quantities, and if there is much precipitate I use a rather larger bulk of liquid. From the above experiment, and also from the results obtained in the previous experiments, it will be seen, as I have always found it, that there is no appreciable loss on reprecipitating the Mg2P207, thus proving the practical purity of the precipitate obtained on the first precipitation. I n order to compare the results obtained by the molybdnte method, 1,000 grains of the Fe203, weighed after ignition, mere dissolved in hydrochloric acid ; and t o this 2.496 grams of ignited Mg2P207 were added ; after solution the whole was reprecipitated by ammonia, washed with distilled water, dried, ignited, and weighed.The above quantity of magnesia salt represents in the iron calculated from the Fe203- Phosphorus per cent. .......... *0994 Phosphorus in iron ............ ,0026 *I020 This gives the actual quantity of phosphorus present. I_ To be q u i k certain that no mistake was made, Mr. Herdsman determined the phosphorus by the magnesia method. Grams of Fe203. Mg,P,O,. Phosphorus per cent. in iwn. 213.27 gave -52 equal -09 72 or difference - -0048 Various portions, from 80 to 150 grains, mere sent t o three of t h e largest steel works in the country, where phosphorus determinatioiiv are made daily, by some of our most expert analysts of iron and steel; two other portions were sent, one to a well known chemist with a mxy large experience in iron a,nd steel analysis, and another to a chemist, also with a large experience, but not so well known.The following are the results returned :- Phospho~*us per cent. by Molybda fe Metiiod. I. Phosphorus per cent. .... -0780 -0821 11. ? 9 .... { } Mean, 00785 1, 111. ,9 >9 .... -0640 11. .:0460 IV. .... -0700 v. .... -0760 obviously low, the mean of the five results is- 7, 9 7 ?, 9 9 Kot taking into consideration the secortd result of No. 111, which is110 RILEY ON THE ESTIMATION OF Phosphorus per cent. .................. *0733 Error in determinations per cent......... '0287 All the results are very concordant, except perhaps No. 111, and all low, thus showing that phosphorus determinations as now carried out by our best operators are too low. The above experiments were partly undertaken in consequence of a statement that my determinations of phosphorus in a steel rail were too high, and also that my results were always higher than those given by the Sheffield Steel Works. Take the rail in question : the phosphorus was determined three times. A. 150 grains of steel gave phosphorus per cent. .... ,094 C. 150 ,, ,, .... -096 B. 200 ,, ,, .... *090 71 ,, 9 9 ?, All the analyses were made by different operators. The molybdate gave, analyses made at Steel Works- ,0602 -0586 A. Phosphorus per cent. ..................{ } *0597 99 .................. -0976 B. ,> C. Y ? Mean by magnesia method. Mean by molybdate. Difference. -0933 -0 722 *0211 thus showing a difference between the results very closely approxi- mating the difference in the previous case. Take another case of same sample bars of steel. Two of my assistants (one now at a steel works) made- I. 11. Magnesia method. A Phosphorus per cent. ................ -17'2 -180 B ,, >, ................ *162 -164 B Repeated by same operator.. .......... *165 -170 Molgbdate method. C Chemist at Sheffield Steel Works returned -867 -273 This high result differing so much from the above, the analyses were repeated, and the following results sent by same chemist :- Molpbdate method. C' Phosphorus per cent. ................ -142 0166 C" ................a154 -154 D Another ironworks chemist .......... -145 ,158 thus clearly showing that the magnesia results are always higher. 17 9 ,PHOSPHORUS IN IRON AND STEEL. 111 I have had a very lengthy correspondence with chemists who have had considerable experience in the determination of phosphorus, mostly with chemists at iron and steel works. The opinion of several is that the two methods may be made to give the same results. This I think is quite possible, as the magnesia process may readily be worked to give slightly lower results. In the case of the molybdate method, I find frequently that dupli- cate analyses are made on the same quantity of steel. Now it is quite possible that corresponding results may be obtained, and that they may be quite wrong, as I regard this as no check OD an analysis. The better way is to take twice the quantity in one case to that taken in the other.Before instituting the above experiments, I have most thoroughly tested the magnesia method, and had every confidence in its accuracy when carefully performed. I have used five times as much steel in one case as another, and obtained corresponding results, and numerous cases double, treble, and so on. The experiments given, made by so many different operators, clearly shew, I think, that as the molybdate process is now carried out, the results are too low. The method is, however, much more rapid tban the magnesia pro- cess, and from experiments I have made, I think the molybdate process may be improved. The method I propose is t'o dissolve the steel or iron in 1-20 nitric acid, avoiding m much excess as possible ; to the solution, diluted to rather more than half a pint, sodium sulphite is added, so as to reduce the iron to FeO after boiling off the sulphite (a large excess should be avoided) ; the phosphorus is precipitated with some peroxide as basic acetate and phosphate, precisely as in the magnesia method ; the preci- pitate is dissolved in hydrochloric acid; the solution made alkaline with ammonia; and the precipitate formed dissolved in 1.40 nitric acid.The solution is then precipitated with molybdate of ammonia in the ordinary way. In an experiment made by Mr. Herdsman it was found that the phospho-molybdate came down at once ; in twenty minutes the preci- pitate had settled ; and in less than an hour after adding the molyb- date, the liquid was filtered, and the precipitate ready to dry. The result obtained was phosphorus -077 per cent. in a steel rail containing by the magnesia method -093 ; it was found that some fnrther precipi- tate of phospho-molybdate was formed on heating the filtrate. Although this experiment was not successful, still I am inclined to think that by allowing a little more time, and with more practice, it may be made to succeed, and to give results more accurate than the112 PICICERING ON THE ACTION OF ordinary process, and in about the same time. I propose carrying out a series of experiments in this direction. I have made no remarks on the method adopted by some chemish of dissolving the molybdate precipitate in ammonia and precipitating the phosphorus by a magnesia salt ; this, in my opinion, is no improvement on the ordinary magnesia mcthod (in iron or steel analjses). I n submitting the above results to the Society, I am under great obligations to the chemists who so readily assisted me in making th& various phosphorus determinations, and also to the aid I have received from my assistants, more especially bj- my senior assistant, Mr. Herdsman, who has in fact carried out the larger nhrnber of analyses I have given.

ISSN:0368-1645    

DOI:10.1039/CT8783300104

出版商:RSC    

年代:1878

数据来源: RSC

摘要:

112 PICICERING ON THE ACTION OF XVII. The Action of Su@liurir Acid on Copper. By SPENCER PICKERIXG. Brackenbury Scholar of Balliol College Oxford. $ I. Although Maurnen6 in 1846 made many analyses of the black substance which is generally formed during the action of sulphuric acid on copper no one up to the present time has made a thorough investigation of the subject it was therefore with a view to throw some light on tlhe nature of this reaction by studying the primary and ultimate products and the circumstances which influence their forma-tion that the experiments detailed below were performed. 8 11. Nature of the Reaction. There appear to be two and only two primary reactions the one resulting in the formation of copper sul phatc sulphur dioxide and water according to the following equation :-1.CU + 2HzSO4 = CUSO~ -+- SO2 + 2Hz0, a reaction which may be regarded as consisting of two stages the first being the formation of copper sulphate and nascent hydrogen, thus-() CU + H2S04 = CUSO~ + 2H, the second being the immediate action of the nascent hydrogen on another portion of the acid forming sulphur dioxide and water, thus-(6.) 2H + HZSO = SO2 + 2EE2O SULPHURIC ACID ON COPPER. 113 The other primary reaction is expressed by the equation-2. ~ C U + 4HzSO4 = CUZS + 3C~S04 + 4H20, and this reaction unlike the former one does not necessitate the previous formation of nascent hydrogen. Of these two reactions either may take place alone or they may both occur together and in various proportions. The other products which are found in the residue insoluble in water and which are not accounted for by these equations are the results of the decomposition of the subsulphide by the hydrogen sulphate thus :-CU~S + 2HZS04 = CUS + CUSO~ + SO + 2Hz0 CUS + 2HzSO4 = S + CUSO~ + SO + 2HzO.It was found that this residue invariably consisted of copper and sulphur only and never contained oxygen as stated by Berzelius and Maumen6 (comp. p. 135). § 111. Mode of Experimenting. The experiments were performed in a small flask of about 100 C.C. capacity the gas liberated being passed through a short wide delivery tube into an ammoniacal solution of silver nitrate as a means of ascer-taining whether any hydrogen sulphide was liberated o r not the temperature of the flask being kept constant by means of a water or oil bath.The acid employed was pure and strong-density 1.843-and it was always raised to the required temperature before the intro-duction of the copper which latter was pure electrotype foil 0.15 mm. in thickness 3 grams exposing in all a surface of 65 square cm. The proportion of the metal and acid employed was 1 part of copper to 10 parts of hydrogen sulphate by weight ; the actual quantities generally used being 3 grams of copper to 16.3 C.C. of acid. The time allowed in the majority of cases was 30 minutes. For the sake of obtaining more strictly comparable results in many instances the same piece of copper was used in several experiments due allowance being made for the relative increase of surface thus exposed ; and for the same reason wherever possible the tempeyature chosen was 100" C.; this tempera-ture being more easily maintained constant than higher or lower ones. § IV. General Appearance of the Action. Sulphuric acid attacks copper at all temperatures from 19' C. (and probably even still lower) upwards to an extent increasing rapidly with the increase of temperature ; with the exception of a few minute and occasional bubbles of sulphur dioxide no gas is evolved from th 114 PICKERINCI ON THE ACTION OF liquid till about 130' as soon as the copper begins to be attacked its surface becomes dull and covered with a film of black subsulphide; when the amount of subsulphide floating in the liquid is small it exhibits a brownish colour similar to that exhibited by small quantities of the protosulphide when suspended in a liquid; but as the quantity of subsnlphide increases the colour deepens and soon appears perfectly black.If the temperature be allowed to rise the liquid generally begins to boil below 300" C. the boiling point of pure strong hydrogen sulphate being 327" ; when the source of heat is withdrawn the sus-pended sulphide subsides leaving a bluish-green solution containing copper sulphate which on cooling crystallises out fi*om the acid in white acicular anhydrous crystals leaving the hydrogen sulphate free from dissolved copper and when the proportion of metal and acid above mentioned is used but little diminished in density. After the copper is entirely dissolved and sometimes even before this a deposit of sulphur appears in the neck of the flixsk.On leading the gas evolved through water collecting that portion of it which remains iindissolved (the remainder being of courbe the air contained originally in the flask &c.) and analysing it it was proved that no gas insoluble in water such as oxygen or hydrogen, was given off from the liquid during the action. A small black precipitate deposited in the silver nitrate solution was at first mistaken for silver sulphide precipitated by evolved hydrogen sulphide but this was afterwards found to be reduced silver sulphite, which latter is precipitated as soon as the ammonia becomes neutra-lised by the sulphur dioxide and it was proved beyond doubt that in no case was any hydrogen sulphide liberated. (a.) By replacing the test tube containing the silver nitrate by another similar tube with a fresh solution whenever the white silver sulphide made its appearance in the previous tube and (6.) By placing a roll of filter paper moistened with a solution of lead acetate in the delivery tube itself and which never became darkened by the formation of any lead sulphide.The copper sulphide appears to be deposited on the metal itself and not in the liquid the coating thus formed on the copper being com-pact and when the metal used is impure difficult to remove. The sulphide shows no crystalline structure but is quite amorphous. In determining its amount it was transferred as quickly as possible by washing and other means to a weighed filter and then carefully dried at 100" C. ; after treating it with carbon disulphide to ascertiain the presence and if present, the amount of free sulphur which it contained, the whole or a portion of it was oxidised by hydrogen nitrate the copper being generally determined by reduction with pure zinc or else by Parke's potassium cyanide method o r as oxide by precipitation SULPHUMC ACID ON COPPER.115 with potassium hydrate ; and the sulphur partially in the free state, and partially as barium sulphate. (From the fact that in all cases where free sulphur was present and estimated as above the snlphide left contained the amount of copper theoretically present in the proto-sulphide I conclude that the sulphur was entirely soluble in carbon disnlphide.) Maurnen6 mentions that the sulphide obtained in this way is “ trks altthble A l’air,” and consequently in washing and drying it used many precautions which I found to be quite unnecessary.This sub-sulphide is not oxidised to the smallest appreciable extent either by washing with water not freed from air or by exposure to air for a considerable time when moist or dry or by drying in a steam bath at 100” C.; though in some cases it was dried over sulphuric acid i 7 b uacuo then washed and dried again at 100” in air to ascertain whether any increase or diminution in weight was occasioned by employing this latter method but none was found to have occurred. The protosul-phide though more oxidisable than the subsulphide is not too unstable to admit of being accurately estimated and analysed in the same way as the subsulphide ; and when formed by the decomposition of this latter, as in the action of sulphuric acid on copper it is more stable than when precipitated from a solution of a copper salt by hydrogen sulphide.Weighed portions of the subsulphide and of the protosulphide ob-tained in various experiments and of the persulphide precipitated by hydrogen sulphide were each exposed moist on filters for 14 days, after which-None of the subsulphide had been oxidised. 1.8 per cent. of the protosulphide (from experiments) had been 9.5 per cent. of the protosulphide (precipitated by H2S) had been Again some of the subsulphide which had been kept in a small bottle for several months on being washed did not yield sufEcient copper sul-phate to give the slightest trace of colour when tested by potassium ferrocyanide although some precipitated copper protosulphide wliich had been kept for the same length of time in a similar bottle showed that 43 per cent.of it had been oxidised. Many other experiments on the oxidisability of the different sulphides gave similar evidence.# f That copper protosulphide varies in the facility with which it is oxidised, according to the method by which it is prepared has been shown by Rose who found that when this body is precipitated from solutions containing copper by am-monium sulphide it is more oxidisable than when precipitated by hydrogen sul-phide. It is generally stated that copper protosulphide is green owing to the pre-sence of copper sulphate but this was shown to be incorrect by preparing solxe copper protosulphide washing it with solution of hydrogen sulphide and drying it oxidised.oxidised 116 PICKERING ON TEE ACTION OF 6j V. Influence of Temperature. After a number of preliminary experiments a series mas made at constant temperatures ranging from 100" to 220" C. ; the time allowed for each being 30 minutes. It was however soon apparent that those performed a t the temperatures 170" 195" 220" C. in which cases the insoluble residue did not consist of copper subsulphide were not com-parable with the others because a t tbese higher temperatures the copper had entirely dissolved before the time allowed had expired and consequently secondary reactions might have taken place. The last ekperiments were therefore repeated diminishing the time of action, so that in each case some of the copper taken might be left undissolved, and the results thus obtained together with other experiments per-formed at lower temperatures are given in Table I.It will be seen on examining experiments 3 t o 9 in this table each of which is the mean of a great number that the amount of copper dissolved in eqnal times (given for one minute in the last column) in-creases rapidly with the temperature and also that the proportion of copper converted into sulphide to that converted into sulphatc dimi-nishes as the temperature is higher till finally at 27'0" C. we get no sulphide a t all formed the action consisting solely of the first of the primary actions given on page 112 namely-1. CU + 2H2S04 = CUSOA + SO2 + 2HZO. It will be seen on examining the second primary action-2.~ C U + 4HzSOJ = C U ~ S + 3CuSO4 + 4H20, that in this the proportion which the copper converted into sulphide bears to that converted into sulphate is two atoms to three atoms and that this is the greatest proportion which could be formed if these two reactions are correct; and also as will be shown below the greatest ratio which could exist according to any theory of the formation of the sulphide. After performing experiments at temperatures from 100" upwards and thus ascertaining that the proportion of sulphide in a current of that gas when it was proved to be green in colour though no sul-phate could possibly have been present in it The protosulphide when obtained in the copper action is rather darker in colour than when precipitated by hydrogen sulphide ; probably owing to the fact that the former is in a more compact state than the latter.It is also stated that copper protoeulphide is not attacked by cold hydrogen nitrate and that the subsulphide is converted into the protosulphide j but this latter is undoubtedly attacked to a considerable extent when dry by cold hydrogen nitrate, and therefore also the subsulphide is in all probability not conrertcd into the proto-sulphide by the action of this acid but both sulphides are attacked to varying and indefinite extents SULPHURIC ACID ON COPPER. 117 to sulphate increased as the temperature was lower it was thought probable that at still lower temperatures the proportion of 2 3 might be reached i.e. that the action (§ I p.112) might be obtained alone ; and although in most cases owing to circumstances not entirely evi-dent this ratio was not obtained still in three instances it was obtained within the limits of possible error; once at 80" C. once at a lower temperatu?e and once at 130" C. with dilute acid. The actual ratios found being-2 2.914 2 2964, besides other instances in which this ratio was nearly attained but in no case was a higher ratio for copper as sulphide to that of sulphate than 2 3 observed. TABLE I. Showing the InjlueiLce of Temperature.* Percentage pro-portion of Copper converted into Percentage cOm-position of insol uble residue. Percent -age of cop-per clis-solved in one minute. Percent-age of Copper dissolved. 5.7 2 -532 1 503 Tempera-ture.Time allowed. 14 days 120 min. 30 min. 30 min. 30 min. 30 min. 30 min. 30 min. 10 min. 2 min. 0.5 min. f afem 1 seconds -cu2s. Cu28 -100 100 100 c u s S. cuso4. 17 '33 5 *25 30 *20 83 -67 94 -75 69 -80 0 0 0 0 0 0 1. 19°C. 2. 60 3. 80 4. loo 5. 124 6. 130 7. 137 8. 150 9. 170 10. 195 11. 220 12. 270 13. 170 14. 195 15. 220 -0 -0003 0 '0211 0 '0501 0 .lo41 0.76 1 -09 1 *17 2 *31 5 -19 26 -75 70 -57 clis-solred in + minute ----75 '00 78 '47 82 '40 83 -00 86 '73 89.18 98 .OO 92 '84 00 .oo 100 100 100 100 100 100 100 100 100 25 '00 21 -53 17 -60 17 *oo 13 -27 10 '82 8 '00 7 -16 to 11 *53 7 *20 2 -136 3 '123 22 *7 32 -6 35 .o 69 -2 51 *92 53.5 70 -57 30 min.30 min. 30 min. 88 '47 92 .SO 97 *S64 0 G 0 -4.17) 100.0 .o*oo 100.0 3.001 100.0 * Columns 3 and 4 in this Table 4 and 5 in Table 11 and corresponding columns in other tables showing the proportion of copper converted into sulplde to that converted into suiphate are made out so as to show the amount of copper originally as subsulphide calculated from the amount of subsulphide protosulphide and free sulphur (see secondary actions) found in the liquid a t the conclusion of the experi-ments 118 PICKERING ON THE ACTION OF The combination of these two primary reactions of which the one takes place alone at high temperatures only the other only at low tem-peratures explains all the results obtained at various interniediate temperatures as given in the first twelve analyses of Table I and equations can easily be formed representing the action in any given case thus the following equations represent approximately the actions which take place at loo" 130" and 170" C.respectively. l l C u + 16H,SO = Cu2S + 9cuso4 + 6S0 + 16H20, ~ C U + 10HZSO4 = CUZS + ~ C U S O ~ + 3502 + 10Hz0, 2 4 C ~ + 42HzSO4 = CU~S + 22CuSO4 + 19SO2 + 42H2O. § VI. Xecondary Actions. The1 ast three results given in Table I were those obtained originally at the temperatures 17O" 195" and 220" C. in all of which ca8es the whole of the copper had been attacked before the time allowed for the experiment had expired thus better opportunity for secondary re-actions was afforded.It will be seen that in none of these cases was there any of the subsulphide left which had been proved by experi-ments given higher up in the table to have been first formed in each case but in its stead a mixture of copper protosulphide and free sul-phur and in other cases not given in the table protosulphide only or a mixture of the protosulphide and subsulphide was found. I n order to ascertain whether the formation of tbese products was explicable by the decomposition of the subsulphide at first formed by the excess of hydrogen sulphate present some of the sulphides were prepared by the ordinary methods analysed and then decomposed by beating with strong sulphuric acid. The protosulphide was attacked by the acid at a temperature as low as lOO"C.and was found by quantitative experiments to break up in the following manner :-GUS + 2H2SO4 = S + G U S ~ ~ + 2Ha0 + SO,. This may be regarded as consisting of the following stages-(1.) GUS + HzS04 = CuSOI + S + 2H, (2,) S + 2H = H,S, ( 3 . ) H2S + HzSOd= SO2 + 2HzO + S, but it seems to be more probable that the second molecule of hydrogen sulphate is decomposed directly by the nascent hydrogen as in the main action of copper on the acid thus-(2.) H2SO4 + 2H = SO + 2H30, and not by the intervening formation of hydrogen sulphide becaus SULPHURIC ACID ON COPPER. 119 (n.) The hydrogen sulphide if formed would probably react on the copper sulphate instead of on the acid. ( b . ) Hydrogen sulphide does not react on hydrogen sulphate at moderately high temperatures with great energy and therefore a con-siderable portion of it would probably be evolved free from the liquid, whereas in reality no traces of it could be detected.For these reasons it is therefore more rational to regard the steps constituting this reaction to be-(1.) CUS + H2so4 = CUSO + S + 2H, (2.) 2H + HzS04 = SO + 2H20. The subsulphide was attacked by hydrogen sulphate at temperatures below loo" breaking up first into the protosulphide and forming at the same time copper snlphate sulphur dioxide and water thus :-(1.) CU~S + HZSO, (2.) 2H + HzSO4 = 2HzO + SO,, GUS + CUSO~ + 2H, and then after the whole of the subsulphide had been decomposed in this manner the protosulphide formed by its decomposition was further broken up with formation of snlphate and liberation of sulphur dioxide and free sulphur as shown above.These decompositions of the protosulphide by the excess of acid present explain all the results obtained in every experiment ; and in various cases every step in the decomposition was traced some of which will be found in the tables below namely cases in which The copper was not entirely dissolved and the black residue con-sisted entirely of subsulphide. The copper was onlyjust dissolved and none of the subsulphide had been attacked. The copper was entirely dissolved and varying proportions of the subsulphide also leaving a mixture of the two sulphides. The copper was entirely dissolved and the subsulphide just con-verted altogether into protosulphide.The copper and subsulphide were entirely dissolved and also the protosulphide to varying extents. The copper and both the sulphides were dissolved and nothing but sulphur left in the liquid. 8 VII. Formation of the Szclphide. The following are arguments :-(a.) That the sulphide is not formed by the action of nascent (1.) I f the subsulphide was produced by the action of nascent hy-1Lydropn 120 PICKERIKG ON THE ACTION OF drogen on the copper sulphate it would be according to the following equations-(1.) ~ C U + 6H:,SOA = GCUSOI + 12H, (2.) 12H + 2CuS04 = CuZS + SO + 6H0, in which case the greatest possible ratio which the copper converted into subsulphide could bear t o that converted into sulphate would be 2 4 whereas the ratio 2 3 is obtainable.(2.) I f nascent hydrogen could react simultaneously on copper and copper sulphate it would be according to the equation-~ C U + 4HZSOI = 3CuS04 + CU~S + 4Hz0, this equation being then composed of two steps. (1.) ~ C U + 4H,SO = ~ C U S O ~ + 8H, (2.) 8H + CU + CUSO~ = CUZS + 4HZO. But that nascent hydrogen cannot react in this way ma'y be proved by treating a piece of zinc with dilute hydrogen sulphate mixed with a solution of copper sulphate in which case no trace of copper subsul-phide is formed although hydrogen is here liberated in the nascent state in presence of metallic copper and copper sulphate. (6.) That the sulphide is not formed by the action of hydrogen sdphide :-(1.) Some hydrogen sulphide would in all probability be given off as such from the liquid and its presence would ha've been easily recog-nised by the solution of silver nitrate.(2.) The hydrogen sulphide would be formed by the previous liber-ation of nascent hydrogen and the subsequent reaction of this body either on the hydrogen sulphate or on the copper sulphate ; if on the hydrogen sulphate the reactions would be represented by the follow-ing formuke :-(1,) ~ C U + 8CuS04 = ~ C U S O ~ + 16H, ( 2 . ) 12H + 3HZS04= HZS + 2SOZ + 8HZ0, (3.) H,S + 4H + 2CuSOa = CuZS + HZSOa + SO2 + 2HZ0, and if on the copper sulphate by the formula+-(1.) 11 CU + 11H,SO = llCuSOi + 22H, ( 2 . ) 18H + ~ C U S O = HZS + CUZS + 8H20, (3.) H,S + 4H + ~ C U S O ~ CUZS + HZS04 + SO2 + 2H20. In the former of these cases the grestest proportion which the copper as subsulphide conld bear to that as sulphate would'be 4 12, and in the latter 4 7 whereas in reality the proportion 4 6 is obtainable SULPHURIC ACID ON COPPER.121 (3.) Hydrogen sulphide reacts on copper sulphate forming copper protosulphide and not subsulphide which latter is the product obtained in the action in question. (4.) The subsulphide is apparently formed on the surface of the copper and not by the passage of bubbles of gas through the liquid. (c.) That the sulphide is not formed by the union of the metallic copper with free sdpuhur previously liberated during the action as stated by Calvert and Johnson. (1.) Since t'he formation of hydrogen sulphide is untenable the sulphur could only be liberated by the actiou of nascent hydrogen on the hydrogen sulphate o r sulphur dioxide present both of which re-actions are improbable and unsupported by fact.(2.) No sulphur is ever found in the insoluble residue produced during the action of hydrogen sulphate on copper till after the decom-position of the copper sulphides and all the experiments performed on the subject prove t'hat this sulphur so far from being the cause of their formation is in reality the product of their decomposition. (3.) If the sulphide was formed by the combination of the copper with free sulphur the amount of it produced would be increased by increasing the quantity of that sulphur ; but this was proved not to he the case by adding a weighed quantity of sulphur to the acid used in one of the experiments; after the conclusion of the experiment the sulphur which had been added was not appreciably diminished in weight nor was the quantity of copper sulphide formed greater than in other similar experiments where no sulphur had been added to the liquid.(It is sometimes stated in t e s t books that sulphur when sus-pended in a liquid as obtained in the preparation of pentathioiiic acid, may be precipitated as copper sulphide by agitation with copper turnings as if the metal combined directly with the sulphur. But the sulphur is in reality carried down with copper sulphide formed by the decomposition of copper pentathionate as shown by W a c k e n r o d e r, who proposed this method.) We may therefore conclude that the snlphide cannot be formed in the way supposed by C a l v e r t and Johnson nor by the action of nascent hydrogen or hydrogen sulphide but that the hydrogen snl-phate is decomposed by the copper directly forming copper subsul-phide &c.I n several experiments where only a mere trace of copper was left unattacked none of the subsulphide was decomposed the reason being obvious namely that the acid would continue to act on the copper as long RS any of this latter remained in the free state and that not till after all the free metal had been dissolved would it attack the sulphide it being much easier for the acid to combine with the VOL. XXXIII. 122 PICmRING ON THE ACTIOX OF Percent,agc composi-t.ion of the insoluble residue. copper in the free state than to decompose a compound body contain-ing it and then combine with the liberated metal.The temperature at which these experiments were performed was above 170" C. i.e. a t a temperature when the brisk evolution of gas would prevent the metallic surface from becoming so densely coated by the deposition of subsnlphide a i d sulphate as to protect it from the action of the acid ; it was therefore anticipated that at lower temperatures when the evolution of gas was slow the coating of subsnlphide and sulphate might be deposited so compactly on the copper that it would protect it entirely or to a great extent from the action of the acid which would then be a t liberty to attack the subsulphide. This anticipation was realised by a number of experiments perfoymeci at various tem-peratures and forvarious lengths of time some of which are shown in Table 11.The protective effect of the coating of sulphide is shown in columns 6 7 and 8 where it will be seen that the amount of subsul-phidc decomposed increases with the duration of the experiment and it is also shown in the last four experiments in column 9 where the amount of copper dissolved during successive intervals of thirty minutes is given. (In this column the first three experiments appear to give evidence contradictory t,o that afforded by the last four but this will be satisfactorily explained below p. 128). TABLE 11. COPP~ dis-solred in Tem-perature. 1. 100OC. 2. 100 3. 100 4. 137 5. 137 6. 137 7. 137 Percent-age of Copper dis-solTed. 3 -336 13 '31 18 *94 40 '20 65 '82 85 -67 99 '50 Time allowed.30 inin. 90 min. 120 min. 30 iiiiii. 60 min. 90 min. 120 min. Proportion of Colqwr con-verted into s. 0 0 0 0 0 0 0 corisecut ive intervals of 30 minutes. 3 -336 4 *987 5 '630 40.20 25.62 19 3 5 13 *83 cu.,s. 18-60 18.14 18.64 16.00 8.60 cuso4 -~ - -81.4 81 -86 81.36 84.00 91.4 - -CUZS. -LOO 6'3.0 51.0 100.0 90-6 72.1 31-16 8 VIII. Proportion of Acid to Metal. The amount of copper dissolved and the relative amount of sul-phide formed are apparently not influenced by the proportion of acid and metal used when these are varied. Thus experiments were made with 1 part of copper to 0.6 5.0 10.0 and 20.0 parts of acid but the means of many results obtained with these several proportions did not vary in any (lofinite direction or differ from each to a greater extent cus.0 4,l.O 49.0 0 9.4 27'9 68-8 SULPHURIC AUID ON COPPER. 123 than did the results of single experiments in which the same propor-tions of metal and acid were employed. § IX. The Water formed. After the action is over the acid is found to contain no copper sul-phate in solution though water being formed during the action it might be thought at first that some of the sulphate would certainly be dissolved since this body is soluble in dilute though not in strong acid. But the fact is that with the proportion of metal and acid used in most of the experiments the water given off would be too insignificant to alter the density of the acid to any considerable degree.Thus supposing that the action in which most water is formed with a given weight of copper namely, CU + 2HZSO4 = CUSO~ + SO2 + 2Hz0, to take place only and that the whole of the copper in the experiment were dissolved the diminution in the density of the acid as found experimentally would only amount to about 0.008. Even a very small proportion of this water is given off at temperatures below 150" C. as mas found by connecting a weighed calcium chloride drying tube with the flask taking care after the cxperirnent to expel the sulphur dioxide by a current of dried air. This increase in weight of the drying tube might possibly have been due to the spray of the acid carried off in the current of gas ; but as the evolution of gas was very gentle and as in other experiments the acid was not found to have experienced quite the theoretical diminution in density it is probable that it was principally due to the water formed during the action.At higher temperatures more water is given oE and it makes its appearance in minute drops in the neck of the flask and in the delivery tube. I n addition to there being more action and therefore more water formed at higher temperatures ibs volatilisation would be augmented by the increased evolution of gas. It was a t first thought possible that owing t o the great hygroscopic powers of anhydrous copper sulphate that this salt might retain the water and form partially hydrated crystals, but this does not appear to be the case because-(1.) The crystals which separat.e out on cooling are perfectly white, like anhydrous copper sulphate and do not exhibit any trace of a blue colour as do all its hydrated salts.(2.) It was found by experiment that when copper sulphate con-taining even 1 molecule of water of crystallisation onl7 was heated with strong hydrogen sulphate that it entirely gave up its water to the acid this latter becoming diluted t o a corresponding degree and the copper sulphate crystallising out in white anhydrous crystals. L 124 PICKERING ON THE ACTION OF That the acid retained most of the water liberated in the majority of my experiments is proved not only by the slight diminution of density observable a t the conclusion of the experiment but also by the fact already noticed that the acid generally boils at a temperature a little below the boiling point of perfectly pure hydrogen sulphate.tj X. The Hydrogen Szclphate used. Some experiments were made to see if the acid actually entering into the reaction agreed with the amount required by the equation. The percentage of true acid in the hydrogen sulphate employed was first determined both volumetrically by a freshly-prepared standard solution of ammonia and gravimetrically as barium sulphate. A weighed quantity of the acid was then heated as in other cases with a weighed quantity of copper. After the time allowed had expired, the acid was diluted and boiled in a current of carbon dioxide to free it from sulphur dioxide. I n order to prevent any acid from being carried off during boiling the delivery tube dipped into another flask containing a little water and this second flask was similarly con-nected with a third flask the contents of both of which were boiled in turn to free them from sulphur dioxide.* The loss in weight ex-perienced by the copper and the amount of copper sulphide formed were then ascertained from which data the equation representing the reaction which had taken place was constructed.The residual hy-drogen sulpbate was afterwards determined and found to agree within experimental error with that required by this equation. Several determinations were made all of which gave satisfactory results. § XI. Determination of the Xulphzcr Dioxide. The equation was first constructed from the amount of copper attacked and the amount of sulphide formed; the gas eliminated from the liquid by boiling as in the determination of the hydrogen sulphate was collected in a large volume of water carefully freed from air by long boiling a, * Beforc the determination of the hydrogen sulphate preliminary experiments were made by w-hich it was ascertained-(1.) That boiling about 100 C.C.of a saturated solution of sulphur dioxide for 30 minutes in a current of carbon dioxide was amply sufficient to free it from all traces of the former gas. (2.) That the two washing flasks were nccessary but also sufficient t o prevent any loss of acid from the experimental flask. (3.) That the copper sulphides were not appreciably decomposed by boiling in weak hydrogen sulphate (1 V O ~ . of acid to 10 vols. of water being the proportion used) for 30 minutes the liquid and apparatus being freed from air and filled with carbon dioxide.The sulphur dioxide evolved was then determined SULPHURIC ACID ON COPPER. 125 current of carbon dioxide being drawn through the a.ppitratus during the experiment. The sulphur dioxide thus liberated and collected was determined either gravimetrically as barium sulphate after oxida-tion by means of bromine or volumetrically by standard solutions of iodine and sodium hyposulphite. Good results were obtained in this case also two of which are given below. In the first of these the primary reactions alone took place the black residue consisting en-tJrely of copper subsulphide ; in the second all the primary secondary, and tertiary action's had occurred the residue consisting of copper protosulphide and free sulphur.I. SOz required (as determined by copper dissolved and copper sub-sulphide formed) = 0.06517 gram. SO2 found = 0.06513 gram. = (39.94 per cent. 11. SO2 required (as determined by the copper dissolved and the persul-phide and sulphur formed) = 0.3419 gram. SO found = 0.3364 gram. = 98.363 per cent.* Thus having determined accurately every factor (with the exception of the water and that necessarily only approximately) on both sides of the equation representing the action of hydrogen sulphate on copper, and the eecondarg action entailed by it and finding these determina-tions to agree perfectly with the explanation above given of this action, there can be little doubt that this explanation is correct and that the explanations given by others to be discussed below are incorrect, since if otherwise in none of these cases could the factors be what experiment shows they really are.§ XII. The Sublimate of Sulphur. The appearance of a small sublimate of sulphur in the neck of the flask and in some cases in the delivery tube occurred as already men-tioned only after the complete solution of the copper ; and since its formation was also observed on decomposing the sulphides of copper by hydrogen sulphate we may conclude that it owes its origin to this latter action and not to either of the primary reactions. Now since no hydrogen sulphide was detected by the silver nitrate solution as being liberated during the decomposition of the sulphides this sulphur In the second one owing to the necessarily small quantity of copper taken and small quantity of the insoluble residue obtained a very sinall error in the determination of the free sulphur would account for the difference of 1-64 per cent.obtained. # Both of these results are within the limits of experimental error 12 6 PICKERING ON THE ACTION OF could not have been formed by the mutud reaction of the hydrogen sulphidc on the sulphur dioxide. This may a t first sight appear a false argument but in observing other similar reactions such as the decomposition of tetrathionates by hydrogen chloride in which the main gnseous product is sulphur dioxide a sinall quantity of hydrogen sulphide being liberated together with it it is seen that a comparatively small deposition of sulphur is accompanied by a comparatively large indication of hydrogen sulphide in a silT-er solution into which the delivery tube is made to dip.Therefore the formztion of the sulphur sublimate in the copper action may be more reasonably attributed to a cause which must inevitably come into play namely the volatility and tendency to creep up the sides of the containing vessel exhibited by sul-phur wheri in a state of fine division. This is supported by the fact, that the sublimate is visible in the neck of the flask in greater quan-tities and long before it is visible in the delivery tube and in this latter only at high temperatures ; whereas owing to the comparative narrowness of the tube if formed by the reaction of two gases on each other it would as in the decomposition of the polythionates, show itself sooner and in greater quantities here where the gases are brought into closer proximity with each other.It is more probable that the free sulphur is expelled from the liquid chiefly owing to its tendency t o creep up tthe sides of the containing vessel and not to its volatility because when a compact piece of sulphur is heated with hydrogen sulphate none of it sublimes till some time after that in tbe liquid has attained its melting point ; whereas if sulphur in the finely-divided state is employed a deposit is observed in the neck of the flask as low as 110" C. Still sulphur is volatile to a certain extent, even a t 100" C. especially when its volatilisation is aided by the evolution of a gas or vapour in proximity to it as shown by the notable smell of this body perceived when drying a precipitate con-taining it in a steam bath or when boiling liquids in which it is sus-pended.$ XIII. I?juence of an Electric Current. The influence of an electric current on copper while being acted on by hydrogen sulphate was then tried chiefly with a view of ascer-taining whether the relative amount of copper sulphide and sulphate formed would thus be altered. This was done in two ways either by connecting the copper with one of the plates of a small Daniell's cell the other plate being connected by a platinum wire with a small piece of platinum foil immersed in the acid or else the copper was made electropositive by simply attaching it to a piece of platinum wire coiled up and entirely immersed with the copper in the acid.O SULPHURIC ACID ON COPPER. 127 course the more electropositive the copper was made the more of it was dissolved in a given time and vice vewd (though the poles wcre not arranged so as to get the greatest amount of action) ; but in addi-tion to this it mas found that when the copper was electropositive the proportion of siilphide to sulphste formed was increased whereas when electronegative the proportion was diminished as shown in Table 111 where the means of many experiments are given. The diminution and increase in the proportion of sulphide to sulpliate formed according as the metal is made electronegative or eleutro-positive respectively is not great but in all cases it varied in the same direction though to a greater or less extent.TABLE 111. ,Showity the Ffeect o,f aiz Electric Cuwent. Tem-perature. 1. 100°C. 2 . 100 3. 100 4. 100 5. 100 6. 100 -Time allowed. 30 min. 30 min. 30 min. 15 min. 30 min. 60 min. Condi-tion. Positive Ordinmy Negative Positive Positive Positive -Percent-age of Copper dis-solved. 14 *214 3,707 3 -2% 6 *978 13 *197 18 *184 Percentage com-position of the insoluble residue. cu,s.l cus. s. - 1 I-Proport ion of Copper as cu,s. CUSOd. l l Percentage of Copper 1 3 s -solved in consecutive intervals of 15 minutea. , I- I It will be observed that when the copper was made electropositive, the sulphide did not consist as in other cases of subsulphide only, but of a mixture of subsulphide and protosulpliide.This is easily explained thus When the copper is made electropositive as much metal is dissolved during the first 15 minutes as is dissolved in about oiie hour when it is not made electropositive or when made electro-negative ; and consequently in the former case as much or even more sulphide (since also the relative proportion of sulphide is increased) is formed as in the latter case ; but as shown above the amount of subsulphide formed during about one hour at 100" C. under ordinary conditions is sufficient to coat the copper to such an extent that it greatly protects the metal and itself become attacked ; consequently, when the copper is made electropositive and the action proceeded with about four times its ordinary rapidity me should expect as is the case? that the sulphide will begin to be decomposed after about the first 15 minutes.The protective action of the sulphide is shown by the last three experiments given in Table 111 where (in the las 128 PICRERING ON THE ACTION OF column) a relatively smaller amount of action is seen to occur as the time allowed is longer. I n order to make sure that in these cases as well as in those already considered the subsulphide was in reality the first product and that the protosulphide owed its origin to the secon-dary reaction and was not produced directly from the copper expe-riments were made with copper rendered electropositive for 5 10 and 15 minutes; always when 5 and 10 minutes and sometimes when 15 minutes were allowed the insoluble residue consisted entirely of subsulphide showing that this was in reality the first product.From the moderately good conducting power of copper sulphide and the fact that being less easily attacked by hydrogen sulphate than metallic copper it would act i n an electronegative manner towards this latter body it was thought probable that the sulphide as i t was formed by making the copper more electropositive would increa,se the actual amount of action during the first stages. That this was in reality the case was proved by performing several series of experi-ments a t the same temperature wit'h the same piece of copper (to make the several results more strictly comparable with each other due corrections being made for the relative increase of surf ace exposed) for successively increasing intervals of time.Two of these series are given in Table IV and tliese may also be taken in conjunction with those given in Table 11 &c. as illustrative of the eff'ect of time on the products of the action. The figurcs in the last column of tliis table TABLE IT. Shouhg the Actio?L of the Szdphide o n the Anxount of Copper Bissolved. Tem-perature. -1. 100°C. 2. 100 3. 100 4. 100 5. 100 6. 100 7. 100 8. 100 9. 100 1. 100 2. 100 3. 100 4. 100 5. 100 -Percent-age of Copper dis-solved. 0 *2001 0 '834 2 -300 3 -336 4 -987 7 -171 7.572 13 *310 18.94 0.513 1.310 3.574 7.206 9 '072 Percentage composi-tion of the insoluble residue.CU2S. -. 100 100 100 100 100 100 59 .o 51 '0 -----_ -c u s . 0 0 0 0 0 0 4.1 -0 49 -0 -Proportion of Copper LlS 3usoq -90 '4 87.25 86 -9 86.7 81 '4 --Percentage of Copper dissolved in consecutive intervals of 5 minutes. -0 '2001 0 %34 0 -767 0.901 0 *825 1 -093 0 -2005 0 *9565 0 *go5 0 -513 0 -797 1-132 0 '932 0 -44 SULPHURIC ACID ON COPPER. 129 sh0.w the additional quantities of copper dissolved in consecutive and equal increments of time and it is thus seen that the amount dissolved increases rapidly a t first then more gradually till after reaching a maximum it begins to decrease chiefly owing as was said above in connection with other experiments,' to the protective action of the coating of sulphide and partially also to the increasing diminution in density of the acid a very small diminution of which is capable as will be shown below of having considerable influence on the amount of copper attacked.I n the series given in Table IV the amount and composition of the sulphide formed was not determined with much accuracy this being unnecessary and indeed with the small amount of action in many cases it would have been impossible t o do so j but as might have been anticipated from the effect of making the metal electropositive by other means the proportion of sulphide to sulphate increases with the amount of copper. acted on i e . with the actual amount of sulphide present. (When the copper acted on is made the negative electrode the pla-tinum which acts as the positive electrode naturally remains bright, but when the current is reversed the negative electrode ( i e .the pla-tinum) becomes slowly coated with a black deposit which as far as can be judged by qualitative analysis (since sufficient of it was not obtained to admit of a quantitative determination) consists of copper sub-sulphide. This evidently arises from the deposition of metallic copper on the platinum which acts as the negative electrode owing to the electrolysis of the copper sulphate in the liquid ; the copper thus deposited soon becomes attacked by the acid in the same way as but to a smaller extent than the copper constituting the positive electrode, thus giving rise to it film of copper sulphide covering the platinum.The prior deposition of the metal may be observed by taking a.bright piece of copper coating one half of it with mercury and then immers-ing it without connecting it with the battery in heated hydrogen sul-phate ; almost as soon as the exposed copper begins to be attacked the mercury acting as a negative electrode becomes coated with a thin film of riietallic copper and if the acid be poured off beiore the action has proceeded too far this deposit will exhibit most beautifully the colours of thin films in which owing to the natural colour of the copper rich purple and magenta tints prevail. I f left in the acid this film soon becomes reddish and finally black consisting then of copper sulphide. These colours first exhibited by the film would prove that a deposition of a layer of nietallic copper must be the origin of the coat-ing of copper sulphide on the platinum or mercury since no such colour can be seen during the deposition of sulphide or) uncoated copper and it is indeed impossible to see how any copper subsulphide could be otherwise deposited on the negative electrode.130 Proportion of copper as PICKl3RISQ ON THE ACTION OF I Percent-age of Copper 0 XIV. Iujlzience of Puw*ty. (a.) Of the MefQZ.-The influence of the purity of the metal used was then studied. The copper employed in the above experiments as already mentioned was ordinarily pure electrotype foil and the nsual tests failed to detect any mctallic impurities in it. Some commercial sheet copper was then taken containing small quantities of arsenic, tin silver iron and lead and substituted for the electrotype metal ; the mean of several experiments with t,he impure metal is given in Table V 5 comparable with 2 of the same table yesults which were obtained with the pure metal under similar circumstances.TABLE V. Showing the Inflzience of Impurity itz the Copper. ~~~~ ~ ~ Quality of Sample. 1. Purest electru-tppc wire . . . . 2. Pure electrotype foil. . . . . . . . . , 3. Less pure elec-troti-pe foil . . 4. Copp& binding wire . . . . . . . . 5. Commercial sheet copper 6. A bronze coin 7. Copper turnings (very impure) ~ ~~ Tem-p m t u r e -looo c. 100 100 100 100 100 100 ~~ ~ Time a1 lo wed, Pcrcezlt,age compo.sition of the insol-uble residue. cuzs. 100 100 100 -83 '3 --cus. The main points that will be noticed in the experiments performed with the common metal are firstly that the insoluble residue does not consist of tlie subsulphide only but of amixture of the two sulphides, and secondly that a far greater amount of the metal is attacked than when pure copper is used. The former of these two results is a con-sequence of t h e latter being explicable in the same manner as when an increase in the amount of action is produced by making the metal electropositive namely that sufficient sulphide is formed in the first part of the reaction to protect the metal considerably from the acid, and thus the subsulphide itself becomes attacked before the action has proceeded far.In this case a s in the others it was proved by making tbe experiment last only 10 or 15 minut>es that the first product was invariably copper subsnlphide only. Tlie reason why much more copper should be dissolved in a given time when im SULPHURIC ACID ON COPPER. 131 pure than when pure is not so obvious. From the near accord-ance of the amount of impure metal dissolved with the amount of pure metal dissolved when rendered electropositive I thought at first to attribute the increase of action obtained when the metal is impure to its being made electropositive by the metallic impurities present in it ; but it was found that this explanation would not hold good from the following consideration :-Far a day has shown that the metals which exist as impurities in commercial copper namely, lead tin bismuth iron antimony,* and silver are with the exception of this last-named metal electropositive towards copper in weak hydro-gen sulphate silver being electronegative towards it ; and as far as can be judged from rough experiments these metals hold nearly the same position in the elect~ochernical series towards copper when the liquid is strong hydrogen sulphate a t a temperature of 150" C.; arsenic and silver being electronegative towards copper since it is improbable that the small traces of arsenic and silver in commercial copper should so entirely counteract the effect of all the other impuri-ties present as to render the metal decidedly electropositive we should expect to find impure copper less electropositive than pure copper towards hydrogen sulphate.The following facts show that this is in reality the case When copper either pure or impure is acted on by sulphuric acid it is found to be in a more electronegative than electropositive condition for the increase in action when made electro-positive is much greater than the decrease when made electronegatire. But when pure the increase when made electropositive is 3;?$ and the decrease when made electropositive is c?.F whereas when impure the increase in action 7i&5 and the decrease f'?g the impure being obvi-ously more strongly electronegative than the pure and thercfore the increase of action caused by the presence of impurity i n the copper cannot be attributed to the galvanic influence of that impurity.In addition to the two main points noticed as above in connection with the purity of the copper it will also be seen that the relative pro-portion of sulphide formed is rather greater when the metal is impure than when pure. I can give no satisfactory explanation of this and can only state that a t the same temperature the relative amount of sulphide formed increases slowly with the amount of metal acted on ; and it would follow from this that the proportional increase of sulphide observed when pure copper is rendered electropositive and zice veysd is not due to the fact of the metal being in a certain electrical condition, but merely to the increased or diminished amount of action owing to that electrical condition. * F a r a d a y did not experiment on arsenic which is also a common impurity in copper but it seems t o be ekctronegatirc towards copper and electropositive towards d v e r in hydrogen sulphate either Btrong or weak 138 PICKERING ON THE ACTION OF The increased relative amount of sulphide formed with impure cop-per is also seen by its forming a notable amount of sulphide at 2'70" C., when the pure metal forms none.Pure copper also when rendered electropositive by being attached to a platinum wire also forms an easily distinguishable amount of sulphide a t 270" C. The best mode of observing it is to string tlie pieces of copper on to a loop of platinum wire fused into a glass rod ; this may be passed through a hole in the cork closing the tube or flask used and gradually lowered into the acid when it has attained the required temperature ; the action is thus rendered manageable and the escaping gas may be conducted away through a delivery tube and be absorbed.On examining the piece of copper after it has been attacked by the acid it is found that when impure the surface is far more rough and uneven than whea pure showing that in the former case the action has been very unequal in contiguous parts owing to tlie presence of impurities. The coating which the sulphides (afterwards becoming attacked and beihg replaced by sulphur) together with the anhydrous sulphate forms first in the rugosities and then over the whole surface, is naturally much more compact than when formed on the even sur-face retained by pure metal throughout the action so much so that after a certain amount of metal has been dissolved the remainder is almost conipletely shielded from the acid and remains unattacked, even after prolonged immersion in the acid at moderately high tempe-ratures.This protective action of the sulphide deposited on impure copper may be shown by the following experiment:-A piece of impure cop-per is immersed in acid in contact with a piece of pure metal both pieces exposing equal surfaces ; being in contact the effect is the same as if the impurity were equally divided between both pieces and each should be acted on t o the same extent but it is foucd that the pure metal is invariably most attacked showing that the impure must have been protected to a greater extent than the pure by the coating of sulphide.Other samples of copper were experimented with and an average of the results obtained with each is given in Table V.* The results obtained at higher temperatures agreed in the several instances with those obtained at 100" C. which are here given. They are arranged, beginning with ssniples which gave the least amount of action and ending with those that gavc the most and the order thus obtained is, a s far as can be judged without accurate quantitative analyses of each * The results given in the table are corrected so as to exhibit the amount of action obtaiued with equal weights esposing equal surfaces to the acid this being the o11Iy way in which eqwriments performed with samples of various thicknesses can be rendered comparable SULPHURIC ACID ON COPPER.133 sample the same on the whole as that which would be obtained by arranging the metals according to their relative purity the greater being the amount of action according as the amount of impurity is greater. (The coin probably contained a considerably smaller per-centage of copper than the turnings but it owes its position in the table to the zinc present in it which would act electronegatively in the strong acid and therefore in opposition to the other impurities.) This fact and the fact that a verysmall amount of impuritlyis capable of causing a great increase in action leads to the conjecture that if such a thing as perfectly pure copper could be obtained it might not he acted on a t all by hydrogen sulphate but from the impossibility of obtaining absolute purity this must f o r the present remain but a mere conjecture.(b.) Of the Acid.-The usual amount of impurity in commercial hydrogen sulphate is too minute to have any appreciable effect on the action ; but if the arsenic usuaWy present in it be increased in amount, it becomes deposited on the copper and being electronegative towards it increases the action.* If the amount of lead is increased no altera-tion is caused in the action since lead is electropositive towards copper in hydrogen sulphate. Ej XV. Actim with Dilute Acids. Table TI exhibits the influence of diluting the acid employed in the experiment,s; it will be seen from it that the amount of action decreases rapidly with the decrease in densit'y of the hydrogen sub phate.The amount of copper dissolved during the time allowed-30 minutes-began to be appreciable a t 130" C. with the acid H2SOa,H20 and at 165" C. with the acid H2S0d,2Hz0 ; though pro-bably if the time allowed was much prolonged an appreciable action would take place a t considerably lower temperatures since the amount of action obtained with the stronger acid at 130" C. and with the weaker one a t 165" C. is about equivalent to that obtained with pure acid at 100" C. No appreciable action was obtained with acid weaker than HzS02,2Hz0. The composition and quantit'y of sulphide formed agreed with the composition and quantity of it formed by strong acid at such temperatures when equal amounts of copper were acted on. The results given in Table VI agree with those obtained by Gal-r e r t and Johnson as near as can be expected considering what minute differences in the purity of the metal and dilution of the acid alter to a great extent the amount of action.* Reinsch's test may thus be effectually performed in hydrogen eulphate elren when weak though it is far less quick in operation than when the liquid used is hydrogen chloride 134 PICKERING ON THE ACTION OF TABLE TI. Showing the Action of Acid of Various Strengths. Percentage of Copper dissolred' Tem-perature. -1. 100OC. 2. 100 3. 100 4. 100 5. 130 6. 130 7. 130 8. 165 9. 165 10. 165 to t6at dissolved by aciod sp. gr. 1.843 at e same tempera-ture and for the same Time allowed. -Density. 1 -843 1 %295 1 *780 1 '620 1 '843 1 -780 1 '620 1 -843 1.780 1.620 1 Proportion dissolved 1 length of time.I--- -2 -380 0 *585 0 0 32 *6 1 *182 0 'Oin 15min. 16 -54 2 '744 1 l 0.246 1 0 l 0 l 1 l 0.0363 1 0 l 1 l 0.018 1 0.11 :'1 § XVI. Variation of Results. The experiments given in the above table are either means of a large number or clse characteristic results selccted from several. It would be superfluous to give the results of more experiments than are here given since they all bear the same evidence as to the nature of the action and the circumstances which influence it. Often in comparing together several results of experiments per-formed as nearly as possible under similar circumstances considerable variation on either side of the mean was observed.From what has been said above it is not difficult to see that this would naturally be the case from the minute and unavoidable circumstances which influ-ence the action namely :-(1.) A very slight change in the density of the acid. (2.) A minute alteration in the amount or kind of impurity in the metal so small that different thcugh contiguous pieces of the same sample of metal may givc considerably different results as is shown by the greater concordance observed when several similar experiments are performed with the same piece of metal than when performed with different pieces of the same sample. (3.) The mode in which the sulphide is deposited; since a small alteration in temperature or in the purity of the metal makes a con-siderable difference in the compactness of the film.(4.) The mode in which the pieces of copper are placed in the liquid ; since it appears that between two pieces touching each other, the film of sulphide and sulphate is deposited so compactly as t o m:ake them adhere together. (The pieces of copper which hare been in contact with each other are invariably thicker after the action tha SULPHURIC ACID ON COPPER. 135 Time allowed. those which have not been in contact and also on the former the sul-phide leaves a darker and more indelible stain than on the latter.) (5.) The difficulty of keeping the temperature of the bath exactly constant for any length of time except the temperature employed be 100" c. (6.) And lastly the fact that the thickness of the copper varies sufficiently (especially when it is in foil as in the majority of the above cases) to cause the same weights of it to show considerably different amounts of surface.But in spite of the impossibility of getting very accurate and con-cordant results by performing a number of experiments in each case,% sufficient concordance is obtained to leave no doubt whatever as to the true reaction. The amount of variation may be seen in Table VII (and indeed in most of the previous tables) where the extreme results obtained in a few classes of experiments are given. Percentage composition Percent- of insoluble age of residue. Copper dissolved. -TABLE VII. Shouting Exteqit of Variation. of Results. 3. Pure 4. Pure ., 5. Pure ,. 6. Pure 8.Impure} " * ' ' 9. Impure . . . . . 7. Impure 100 100 135' 137 100 100 100 __I-I 1 tugs. 90 ) 97.0 90'6 90 , I 85.6 1 72.1 cus. Proportion of Co;Fper as I cu,s. cuso4 -- I - - I - 14.58 85 -42 18 *18 1 81.82 18.12 I 81 *88 16 so0 j 84 .oo $ XVII. Othei- Opiiiions as to the Action. The explanation of the action of sulphuric acid on copper given above is a t variance with t,hose already given by others who have studied the reaction. Berzelius (Tratite'de Chimie iv 324) mentions the formation of a black insoluble powder oxidisable by hydrogen nitrate and which * I have performed about 250 experiments on this subject. t Same piece of copper used in both experiments 136 PICKERING ON THE ACTION OF " appears to be " copper subsulphate though this body requires only 56-76 per cent.of copper whereas the copper in the residue after the extraction of free sulphur is never less than 66.316 per cent. in addi-tion to which recent experiments show that copper subsulphate is a soluble and not an insoluble body. B a r r u e l (Journ. de Pharnz. xx 13 1834) showed that the action between copper and sulphuric acid takes place at ordinary tempera-tures if sufficient time be allowed ; though he obtained a far smaller amount of action than that given in Table I. He states as has also heen noticed above that a t low temperatures the sulphur dioxide formed is dissolved in the liquid and he considers that this reacts on the copper forming protosulphide and protoxide of copper the latter afterwards dissolving in the acid.The only experiment which he adduced in support of this view was to enclose some copper in a her-metically sealed tube with some sulphurous acid. After six months a brownish body appeared in the liquid containing sulphur and copper, and whicli there is no reason to doubt was a sulphide of copper. But though sulphur dioxide in sohition may attack copper under certain circumstances still it is not difficult to prove that in the action of sul-phuric acid on copper it does not do so to any appreciable extent for if some copper be heated in an aqueous solution of hydrogen sul-phite and a constant current of snlphur dioxide be drawn through the liquid during the experiment it will be found that the copper remains perfectly untarnished and nnattacked whereas under similar circum-stances but using hydrogen sulphate instead of hydrogen sulphits a large amount of copper is found to have been dissolved and converted into sulphide.Rarruel like Berzelius does not appear to have made any quantitative analyses of the black residue. Maurnen8 (8.12~. Chim. Ph?ys. 1846 3rd series xviii 311) after performing several analyses of the insoluble residue arrived at the fol-lowing conclusions as to its formation and composition :-That besides the main reaction forming copper sulphate sulphur dioxide &c. there is another distinct reaction consisting of four dis-tinct steps and giving rise to four different bodies-(1.) Copper subsulphide Cn,S. (2.) An oxysulphide of copper Cu0,2Cu2S 01- Cu,S,O. (3.) Another oxpsulphide of copper CuO,2CuS or Cn,8,0.(4.) Another oxysulphide of copper CuO,CuS or Cu,SO. The first of these steps namely the formation of the subsulphide is the same as that which I consider takes place. As regards the other steps it is difficult to understand how Manmen6 failed to see that) the percentage of copper and sulphur together invariably made up 100 per cent. of the black residue. Th SULPHURIC ACID OX COPPER. 187 explanation perhaps lies hid in an unintelligible passage which occurs in his paper (p. 316) in which he mentions that granulating the copper was an expedient whicli he used to render easg the separation of the oxysulphide from the unattacked copper and at the same time to prevent any copper remaining unattacked. In the same passage he refers to a “ matter insoluble in acids,” which existed i n large quanti-ties in the copper turnings which he employed ; this matter concen-trated itself in the copper sulphides increasing their weight by as much a,s one-twentieth and in many of his analyses he made allowance for this though in what way he does not state.The first oxpsulphide contains nearly the same percentage of copper as the subsulphide ; the others contain percentages intermediate between that of the sulphide and protosulphide. Thus-Cu2S contains . . Cu 79.814 S 20.186 0 0.0 CuO.ZCu,S contains Cu . . 7!>-82l S . . 16.150 0 . . 4.029 cuo.2cus ?> Cu 70.356 S 23.726 0 5.918 c u 0 . c u s )) Cu . ‘72.511 S 18.339 0 9.150 cus ? ? Cu 66.408 S 33.592 0 0.0 The last three steps which he considers to take place suppose the formation of three bodies the existence of which has never been proved and is not supported even by the majority of his own analyses, as he says that the percentage of copper or sulphur required by the formuls Cu4Sz0 Cn,S,O Cu2SO were never exactly obtained by him and the strongest proof which he adduces for the formation of these bodies is the fact that Pelouze has shown the existence of a body 5CuS,CuO.If Maumen6 had let the action continue longer, he would have ascertained that the last state of the residue is by no means one in which the copper- amounts to as much as 72.414 per cent. but only to 66.316 and taking into consideration the free sul-phur which he does not appear to have recognised indefinitely less.In addition to the improbability of copper oxide being formed and remaining unattacked in presence of excess of strong hydrogen sulphate the following experiment disproves its formation. A piece of copper bent at right angles was placed in a large watch-glass containing hydrogen sulphate so that half the metal should be im-mersed in the acid and half should project into the air the whole heing placed under a bell-jar t o prevent diminution in the density of the acid by absorpt,ion of moisture from the atmosphere ; the portion of the metal in the air being unacted on or acted on only to a very small degree performed the part of an electronegative metal towards the copper in the acid which becoming thus more electropositive was acted 011 to a greatly increased extent (on an average about five times as much as if it was entirely immersed) ; and instead of the relative VOL.XXXIII. i 138 PICKERIKL'G ON THE ACTION OF SULPHURIC ACID ETC. proportion of sulpliide formed being increased as when rendered electropositive under other circumstances it was greatly decreased, so that only a trace of it could be discerned. Now this could not be due to the fact of the copper being made electro-positive since doing so incyeases the amount of sulphide ; it must therefore have been due t o the copper sulphide being oxidised a t the time of its appearance by the oxygen which would be liberated at the surface of that portion of the copper which is immersed in the acid since the whole arrangement would form a galvanic cell consisting of a metal a liquid and a gas.If therefore this black residue consists of or contains copper oxide it i 3 wholly imonceivable that the action of more oxygen can diminisli the amount of oxide formed especially when this oxide according t o Maumen6 is the peroxide. The fact that the presence of free oxygen will diminish the proportion of the insoluble residue was also shown by acting on some copper first with acid carefully freed from oxygen by boiling and by passing a current of carbon dioxide through it and then with acid through which a current of air was passed throughout the experiment a larger proportion of sulphide being formed in the former than in the latter case. The determinations of the sulphur dioxide made also give conclusive proof that the residue can contain no oxygen.The fact already noticed that the sulphide is a t first of a brownish colour does not argue at all that any body besides the sulphide is formed nor does Maurnen6 consider it to do so since he agrees with me that a t the time when the brown colour is niost conspicuous the body consists undoubtedly of copper subsulphide only ; the brown colour at first visible appears to be due merely t o the smallness of the amount of the subsulphide present which moreover is exactly similar to that produced by a small quantity of the protosiilphide when suspended in a liquid. Unfortunately Naumen6 gives no particulars as to the circumstances under which his cxperimeuts were performed so that they cannot be repeated. Calvert and Johnson (Jourm. Cham. SOC. xix 435 1866) per-f'ormed a few experiments on the relative effect of strong and dilute sulphuric acid 011 copper at temperatures of 130" amti 150" C. the re-snlts of which as mentioned above agree moderately well with those given on p. 134. T h y mention the formation of copper subsulphide, and consider it to be due to the liberation of free sulphur which latter afterwards combines directly with the metal. This view they sup-ported by no experinleiits on the subject or analyses of the sulphide, but held it for the following reasons :-(1.) No hydrogen sulphide is evolved. (2.) Sulphur is volatilised GLADSTONE AND TRIBE ON THE ACTION ETC. 139 (8.) From the similarity between this action and that of sulphuric acid on tin, The first two of these reasons have already been discussed and much weight can scarcely be given to the last reason when in the account of their experiments on the action of hydrogen sulphate on tin given in the same paper they state “that hhe action of various strengths of sulphuric acid upon tin differs entirely from that which they exert upon copper.” They failed to obtain any action below 130” C. and considered that none took place in spite of the fact that Barruel as early as 1834 had proved that it took place even at ordinary atmo-spheric temperakures. Experiments detailed above show that tthe difference in action obt,ained at low temperatures (except indeed where the action 5Cu + 4H,SO = Cu,S + 3CnS0 + 48,O alone takes place) up to 270” C. is one of degree only and not of kind

ISSN:0368-1645    

DOI:10.1039/CT8783300112

出版商:RSC    

年代:1878

数据来源: RSC

摘要:

GLADSTONE AND TRIBE ON THE ACTION, ETC. 139 XVIII. An, Inquiry ilzto the Action of the Copper-zinc Couple on Alka- line Ozy-salts. By J. H. GLADSTOKE, Pres. C.S., F.R.S., and ALFRED TRIBE, F.C.S., Lecturer on Chemistry in Dulwich College. PART I. IN 1873 Professor Thorpe established the fact that the copper-zinc couple in presence of nitre and water converts the whole of the nitrogen of the salt into ammonia. Some months prior t80 the publi- cation of his paper it had been noticed by ourselves that the couple quickly reduces an aqueous solution of this salt to nitrite of potassium. This reduction first to nitrite, then to ammonia, is of considerable interest, and appeared to us t o call for a more extended study. A close observation of the course of the chemical change we thought might reveal Dr.Diver’s hyponitrite about which so little is known, and perhaps lead to the real explanation of this and similar reactions, about which nothing definite has yet been ascertained. The couples used in this research were made by adding 100 C.C. of a 2 per cent. solution of copper sulphate twice to every meter of zinc foil 5 centimeters wide. Potassium Nitrate. We give the details of two experiments on the reduction of this salt. The nitrite ar;d ammonia were each estimated daily at about the same Y 2140 GLADSTONE AND TRIBE ON THE ACTION OF TEE ICNOZ. 0 '6'73 0'820 0.778 0.704 0.589 0'347 0.150 Jsil hour ; the ammonia by the Nessler method, the nitrite by potassium permanganate. In the first experiment 4 meters of foil were used, and 500 C.C. of a 1.2 per cent.solution of the salt; in the 2nd, 8 meters of foil and 640 C.C. of a 2.4'7 per cent. solution. The results are given below :- NH,. -- 0 -012 0.025 0.03 0-0425 0'0'72 0'1212 0.184 - Ezpt. I. ~~ Time. 1 day .......... 3 days.. ........ 4 ) , .......... 5 ,, .......... 6 ,, .......... 7 ,, .......... 7 days 12 hours.. 8 ,) .......... 4 hours ........ 1 day .......... days.. ........ 4 ............ 5 ............ 5 days 6 hours . . >> - . * . * * ' * ~~~~~ ~ remperature Centigrade. 15'-17" 1 , 9 ) 7) ), >, 9 9 )S 1'1 13 14 14 ' 5 14 5 15 -5 17 0 '526 1 -182 1,429 1 -587 1 *587 0-758 Nil - 0 -006 0 -022 0 '036 0.0456 0 -07 0.256 0 *40 Equal to KN03 reduced. --- 0.871 gram 1 *lo3 ), 1.132 ,, 1-24 ,, 1-123 ,, 1-09 ), 1.127 , l - 0.66 ,) 1.535' ), 1.912 ,l 2.157 ,, 2.302 )) 2-422 ), 2.376 ,, iVork done each day expressed n rnil1igra.m~ of Hy dr0qen.x 107 % 23 -3 6 .6 19 -5 51 -3 78 *6 215 - 583 '6 241 *7 74 *2 47 62 -5 342 *4 955 '2 During the progress of the experiments, hyponitrite was tested for with silver nitrate twice daily, but in every case with a negative re- sult. The amount of permanganate used up in the estimations during the latter part of the action, jointly with the ammonia formed, points not only to the non-formation of this hyponitrite, but also of any body requiring for its oxidation more permanganate than the nitrite. It starts some- what energetically, then diminishes considerably, again increases, and finally ends more rapidly than it began. Ammonia and its equivalent of potash increase but slowly from the commencement until the time when the maximum amount of nitrite is produced, when this salt rapidly gives way, accompanied of course by an increasing amount of The course of this chemical change is remarkable.* Calculated in accordance with equations :- (a.) E N 0 3 + H? = HyO + KNOa, (b.) KNO, + HB = KHO -t ZHSO + NH,.COPPER-ZINC COUPLE ON ALKALINE OXYLSALTS. 141 the alkalies. This rapid breaking down of the nitrite is coincident with the renewed activity of the couple, and it might therefore be thought that it is a consequence of the smaller stability of the nitrite ; but this can scarcely be the explanation, since we see that almost from the very commencement the couple elects to deoxidise the nitrate, when it has the opportunityof attacking the nitrite.'The question therefore arises, are the variations in the amount of the action, especially the acceleration, due to the ammonia and pot- ash produced P The following series of experiments show the in- fluence of these bodies on the amount of hydrogen set free. The first column represents the hydrogen from a couple immersed in water alone ; the second and third from similar couples immersed in similar volumes of aqueous solutions of NH, and KHO respectively. The strengths of the solutions of ammonia and potassium hydrate in each set of experiments approximate t o the equivalent proportions. The gas measurements were taken after two hours. In Expt. A, the strength of NH, used was 0*026 per cent. ; KHO, In Expt. B, the strength of NH, used was -0256 per cent.; KHO, I n Expt. C, the streugth of NH, used was 0.51 per cent.; RHO, I n Expt. D, the strength of NH, used was 20.0 per cent. ; KHO, 0.087 per cent. 0.846 per cent. 1.69 per cent. 65.8 per cent. Taking the action of the water couple in each set of experiments as unity, the numbers below express the relative quantities of hydrogen obtained :- Water. Ammonia. Potash. A ............ 1 1.8 2-0 B ............ 1 1.75 2-75 c ............ 1 0.91 2.27 D ............ 1 0-36 1-59 from which it appears that the two weakest ammonia solutions aug- ment the action, while the stronger undoubtedly diminish it. The influence of potash is always an accelerating one, but the effect is a t the maximum when the alkali is present in comparatively small quan- tity.These unexpected results were corroborated by the following series of experiments with different strengths of the alkalies. In I, ammonia, 0.21 per cent. was used; in 11, 0.41 per cent. ; and in 111, 0.78 per cent. I n IV, potash, 0.65 per cent. was used; in V, 1.27 per cent. ; and in VI, 2-12 per cent.142 GLADSTONE Ah'D TRIBE ON THE ACTION OF THE i Temperature. Time. 1 Hydrogen in C.C. reduced to 0" and 'I60 mm. ! ___ Ammonia. Potash. 4 hours.. 20 ), .. 68 ,, .. I. 12" 46 11*3* 175 12" 1 544 2 hours .. 14' 75 18 12 -5" 358 66 :: ::I 13" 1 1055 111. - - - 12 133 861 11. IT. v. ---- 55 60 160 175 455 522 36 28 205 210 645 817 --~-- 36 128 442 50 303 888 TI. 45 135 416 23 195 743 -- The ammonia produced in the reaction cannot, it is evident, be the cause of the diminution or of the acceleration already noticed, because where the diminution occurs, the ammonia present would increase the action, and where the increase occurs, it would occasion a de- crease.Potash does augment the production of hydrogen, but this throws no light on the cause of the diminution, and only partially accounts for the great amount of reduction a t t'he end of the reaction : for it appears from our experiments that the maximum amount of hydrogen obtainable per day from couples with water corresponding with those used, amounts to 24 milligrams. And leaving out of con- sideration the influence of the ammonia-which in general is a retard- ing one-the potash produced in the reaction might give 66 milli- grams of hydrogen, whereas thc reduction of the last day in Expt.1 is equal to 107.2 milligrams above that of the first day, whilst in that of Expt. I1 it is 185.8 milligrams for the same quantity of couple. This reduction to nitrite may be shown to an audience as fol- lows :- Pour a solution of nitre-about 10 per cent.-with enough copper sulphate to colour the liquid distinctly, on to some granulated zinc in a tap-funnel ; leave it for a few seconds, and then run off some of the liquid, when the green colour of copper nitrite will be evident. Drop the remainder of the liquid into some starch-solution with potassium iodide and acetic acid : the blue iodide of starch will be instantly formed. F o r this purposeadd to about 5 C.C. of solution 12 drops of copper sulplzate and four or five pieces of zinc foil (1 x 6 inch).Wait about three minutes, then pour the liquid, or a part of it, into about 5 C.C. of starch solu- tion containing a little potassium iodide and acetic acid. A blue coloration forms at once, or in a second or two. By inverting the test- tube containing the test before pouring off, the liquid will be seen to The reaction may also be utilised as a test for nitrates.COPPER-ZIKC COUPLE ON ALKALINE OXT-SALTS. 143 be green. Confirmation may be had by pouring some Nessler reagent into the completely decolorised solution. The reaction with starch can be readily and certainly obtained with 1 part of nitre in 500 of water, and the Nessler reaction with 1 part in 10,0!)0. PART 11. At least three views may be taken of the foregoing change :- I.It may be considered that the zinc, augmented in its activity by contact with the copper, combines with the oxygen of the nitrate. 11. That the zinc and copper electrolyse the water present, and that the nascent hydrogen set free effects the reduction in the vicinity of the negative metal. 111. That the two metals electrolyse the nitrate of potassium, with formation of nitrate of zinc, the reduction being effected a t the nega- tive pole through the agency of the potassium. The first view may be expressed by the following equation:- KNO, j- Zn = ZnO + KNO,, while the further action requires the intervention of water, with the following result :- KNOz + 3Zn + 5H,O = KHO + 3Zn(HQ)2 + NH,. Of course this may be brought about by the formation of interme- The second view may be represented thus- diate compounds.(..) Zn I OH, 1 Cu= ZnO 1 H, ] Cn, ( b . ) KNO, + H, ( c . ) KNOZ + He = HZ0 + NH, + KHO. HZO + KNOZ, And the third view thus- Zn I NO,K I NO,K 1 Cu = Zn(NOJ2 [ K, I Cu. J t may be conceived that this potassium is actually set free and at once acts upoii the water, thus- K, + 2H2Q = 2KH0 + H,; or other combinations of the elements present may be easily conceived to take place with the same final result. The KHQ and Zn(N03)2 produced would of course react, with formation of zinc hydrate and potassium nitrate, so that the sereral changes at each cycle produce a molecule of hydrogen or its equiva- lent, which acts on iiitre in accordance with equations b and c. With reference to the first view, it was found that powdered zinc144 GLADSTONE AND TRIBE ON THE ACTION OF THE and dry nitre, when heated together, detonate explosively, a quantity of gas-probably nitrogen-being produced, together with a solid, consisting of zinc oxide and potassium nitrite and oxide.And Schon- bein and Divers have shown that a solution of nitre is reduced by metals more positive than zinc to potassium nitrite and ammonia ; but in this case it must be borne in mind that hydrogen is simultaneously produced by the decomposition of water. Again, an experiment suggested itself which we hoped would assist in deciding between this and the second and third views. A boxwood cell was cut vertically into two equal parts, some pieces of parchment paper were placed between these, and the divisions of the cell held firmly together by a clamp.A solution of nitre was placed in each of the divisions, a strip of zinc being placed in one, a strip of platinum in the other. The strips were connected together by a metallic wire, and allowed to remain so for two or four days, the action being a feeble one. The general result of several experiments was, a little ammonia in each of the divisions ; free potassium hydrate in the platinurn one, none in the zinc ; and about ten times less nitrite in the platinum than in the zinc division. This great increase oE nitrite in the zinc division would appear to lend material aid to the first view, which requires the reduction to take place by, and in the immediate vicinity of, the zinc plate. At this stage it occurred to us that this reduction might, after all, be due to a couple action, the negative element of such couple being the impuri- ties in the zinc itself; and on trial, we found that similar zinc, when not connected with platinum, reduced nitre to almost the same extent as when metallically associated with that metal as described above.Moreover, we found that equal quantities of granulated redistilled zisc and commercial zinc placed in contact with equal volumes of nitre solution gave in equal times nitrite in the ratio 1 : 2.7. No deduction can therefore be drawn from the presence of the proportionately large amount of nitrite in the zinc division of the cell. That an electric current traverses the nitre solution in the cell ex- periment, from the zinc to the platinum in the liquid, was ascertained by including a galvanometer in the circuit, which, in conjunction with the appearance of potassium hydrate in appreciable amount along with an excess of unaltered nitre in the platinum division, lends, we think, material aid to hypothesis 111. Whether hypothesis I or 111 be the more tenable may not be con- sidered yet decided, but the results exhibited in the following table of a series of comparative experiments on the action of the couple on water, and on solutions of potassium nitrate and nitrite, certainly point to the untenability of 11.COPPER-ZISC COUPLE ON ALKALINE OXY-SALTS.145 Employed for No. 1 KNOr, 500 C.C. of -922 per cent. 9 9 9 , No. 2 7 7 481 7, 9 7 -956 7, 9 , ,, No. 1 KN03, 435 ,, ,, 1.25 ,, 9 , ,, No. 2 ,, 462 ,, ,, 1-18 ,, For comparison the total work done by the couples in the given times is expressed in milligrams of hydrogen. 1.31 -7 106 124 183 222 234 237 296 331 No obs 2. 34 -6 ---- 108 144 193 239 ervation 247 243 369 - KNO,. 28 29.4 45 46 93 87 101 93 117 108 141 132 148 136 165 153 KN03. 24 -4 39 73 84 96 116 120 134 1. ~~ 40 -2 118 200 209 273 293 - - - - 2. 33 -8 -_I 106 198 211 247 272 309 - - - It is evident that the nitre does not simply remain passive, and allow itself to be reduced by the hydrogen evolved from the direct decomposition of water by the couple, which hypothesis I1 requires : for were this the case, the reduction of the salt, a t least at the begin- ning of the action, would be equivalent only to the hydrogen set free from the water couple alone, whereas the oxygen actually removed is equivalent t o about 29 times that amount.It is noticeable that the first numbers given by the nitrite and the nitrate are nearly the same, and that in the respective columns of the salts they do not diverge much from one another for some time, which is of considerable in- terest, as showing that the ammonia and potassium hydrate, which must pour into the solution in the nitrite experiment from its very commencement, do not materially augment the action of the couple. The weight of evidence certainly inclines to hypothesis 111, which is to a great extent confirmed by the following experiments. ElectToZysis of Nitrate of Potassium. I. A V-shaped tube was used, the bend being well plugged with fine asbestos. About 25 C.C. of a 5 per cent.solution of nitre were poured into each of the limbs. An amalgamated zinc plate 1.5 centimeters wide, connected by a wire with the platinum end of 4 Grove’s cells, was immersed to the depth of one decimeter in one limb of the tube, a copper plate, of double the surface connected with the zinc end of the146 GLADSTOKE AND TRIBE ON THE ACTION OF THE battery, being placed in the other. The current was allowed to pass through the liquid for four hours. A trace only of gas escaped from the copper electrode, in the vicinity of which alkali was found imme- diately after making connection. A quantitative examination of the solutions in the respective limbs gave, in addition to the undecornposed 11 i tre- Zinc limb . . . . . . . . 0.3273 gmms Zn(N03):! 0.197 ,, KHO Copper limb .. . . . , 0.0765 ,, KNO, { 0-00375 ,, NH3. The amount of zinc nitrate was ascertained by precipitating the metal as carbonate, and calculating the oxide subsequently obtained as nitrate. Had zinc oxide been produced in this experiment and passed into solution, this method of analysis would give a quantity of nitrate greater than that actually present. The question therefore amrose, does zinc oxide form in the experiment? and, if so, does it dissolve in a solution of nitre op zinc nitrate ? We agitated zinc hydrate with nitre solution, also boiled the substances together. No zinc passed into solution. Small quantities of zinc hydrate were agitated with a solu- tion of zinc nitrate. None disappeared. Schindler also states (GnzeZirz, v, 34) that zinc oxide when boiled with the nitrate does not dissolve. Again, zinc oxide was looked for on the zinc plate, and in the solution in its neighbourhood, during the action in this and subsequent expcri- ments. Not a trace could be seen even when 20 Grove cells were employed.Every NH3, therefore, represents 4 of the ZII(NO,)~ estimated as described, as seen by the equation :- (u.) 4Zn I 8N03K I Cu = 4Zn(NO,), I K, 1 Cu ( b . ) 8K + GH,O + KNO, = 9KHO + NH,, and every KNO, represents one of zinc nitrate, thus :- (c.) Zn I 2N03K I Cu = Zn(PU’03)2 I I(, I Cu (d.) K2 + H,O + KNO3 = KNO2 + 2KHO. Calculating then the ammonia and nitrite found in the copper limb into zinc nitrate, according to these equations, we obtain 0.397 gram of that salt, which is 0.01 in excess of that found in the zinc limb by analysis, and equal to 0.0043 gram of zinc oxide-a quantity which might have formed on the zinc plate and yet have escaped detection.I n other respects it was similar to the last. 11. A 3 per cent. solution was used in this experiment. Found in zinc limb.. . , . .. . 0.2596 gram !&I(NO~)~ 0.1366 ,, KHO KNO, 0.00294 ,, NH,, Copper limb . . . . . . . . . . . . 0.05355 ,,COPPER-ZINC COUPLE ON ALEALINE OXY-SALTS. 147 Nitrate. Chlorate. 1st hour .... 1 : 1-15 3rd ,, . .. . 1 : 2.50 the two latter of which products give 0.2501 gram of Zn(N03)2, which is slightly less Bhan that found. 111. A 3 per cent. solution was used, the current passed for three hours. In other respects similar to I and 11. Found in zinc limb . .. .. . 0.1645 gram Zn(NO& 0.0542 ,, RHO Found in copper limb . . . . 0.03706 ,, KNO, { 0.00157 ,, NH3, the latter of which are equal to 0.1524 gram of Zn(N03)2, which is again below that actually found by analysis. We may therefore con- clude, that in these experiments nitre alone suffered electrolytic de- composition. One other point is worthy of notice here. I n the experiments just described not a trace of nitrite or ammonia could be detected in the zinc limb, which we t.hink finally disposes of hypothesis I, because, if the zinc electrode, when charged with positive electricity, fails to reduce nitre in its immediate vicinity, the zinc of the couple so charged might reasonably be expected not to act. Of course we do not contend that in these electrolytic experiments we have identically the same conditions as obtain in the couple decompositions, but that we have a similarity of condition no one can doubt.Nitrate. Clilorate. 5th hour .. .. 1 : 3.86 21st ,, . . . . 1 : 2.97148 GLADSTONE AND TRIBE ON THE ACTION OF THE electrolysed by an external battery, alkali may a t once be detected close to the negative electrode, but instead of the potassium chlorate being reduced to chloride, the greater part of the hydrogen escapes a.s gas. Employing the arrangement as used for the nitre solution, a current. of four cells gave in four hours 0.00244 gram of potassium chloride in the copper limb, and 0.4775 of zinc chlorate in the zinc limb. Calculating the equivalent of the potassium chloride found according to the equa- tions- ( U .) 3zn I 6C103K I C U = 3Zn(C10,)2 I K6 I CU. (b.) &, + 3820 + KCLO, = GKHO + KC1. we get only 0.0228 of zinc chlorate. Therefore 95.2 per cent. of the hydrogen formed in the experiment passed through the liquid. About four years ago it was pointed out by one of us (Chem. Soc. Jour., 1874, p. 415) that finely divided copper, immersed in acidulated water, agglomerated-that is, formed into more or less coherent lumps- when subjected to the action of nascent hydrogen : also that the finely divided particles of palladium and platinum-metals known to con- dense hydrogen, agglomerated, when similarly treated ; further, that the agglomerated copper, palladium, &c., deglomerated when treated with nascent oxygen:-from all which it was inferred that the copper of the couple was also capable in a slight degree of absorbing hydrogen gas.Graham has shown that occluded hydrogen is a somewhat powerful reducing agent ; and to us, having traced the reducing action of the couple in some way to hydrogen, it appeared of exceptional interest to ascertain whether hydrogen associated with the finely divided copper of the couple could reduce nitre t o nitrite. With this object some copper was precipitated by immersion of a zinc plate in a 2 per cent. solution of copper sulphate till decolorised. As has been already pointed out, the deposit thus obtained contains metallic zinc. To remove this and to charge the residual metal with hydrogen, dilute sulphuric acid was added, which immediately brought about a power- ful agglomeration of the copper.After standing with the acid for about an hour, with occasional shaking, the metal was well washed, and some nitre solution added, when almost immediately the whole deglomerated, shrinking in volume to about a quarter. The solu- tion contained a small quantity of both ammonia and potassium nitrite, which was found equal per 100 grams of copper to 4 milligrams of hydrogen. For the next trial copper was deposited as before, but from a 1 per cent. solution of the sulphate. The deposit was treated with succes- sive portions of copper sulphate for some hours. The residual metal was then divided into two portions. To one, some nitre solution was added; to the other some dilute sulphuric acid. This after shakingCOPPER-ZINC COUPLE OX' ALKALINE OXT-SALTS.149 was poured into a dish, at the bottom of which was a sheet of platinum in connection with the zinc end of 4 Grove's cells. As soon as the metal had settled, the positive electrode was dipped into the acidulated water near its surface. The copper slowly agglomerated without ma- terial change in colonr, and in about 30 minutes hydrogen was freely escaping from it. After washing this a few times, and neutralising with potassium hydrate, a quantity of nitre was added equal to that added to the first portion. Ammonia and nitrite were found in both. The portion not treated with hydrogen gave, per 100 grams of copper, 3.5 milligrams of hydrogen, the agglomerated giving, for a similar quantity of copper, 8 milligrams of hydrogen. Zinc was also found in small quantity in both, but the non-agglomerated contained at least four times the amount of that present in the hydrogenised. Another effort was made to get the finely dividedcopper free from zinc. Some deposit, obtained as in the last experiment, was digested, with occasional shaking, for three days with about 5 per cent.solution of copper sul- phate. It was then well washed and divided into two parts. To one some nitre was added, The other, previously to the addition of an equal quantity of this salt, was digested with dilute sulphuric acid for am hour, washed, again mixed with dilute acid, hydrogenised for two hours, and the adhering acid neutralised with potash. The non- hFdrogenised contained nitrite and ammonia, equal, per 100 grams of copper, to 2.7 milligrams of hydrogen.The hydrogenised portion, for the same amount of copper, contained 19.3 milligrams of hydrogen. Both portions still contained a small quantity of zinc-whether as nietal or oxide, or both, there is no means of determining. It is certain that some oxide existed in the portions not treated with acid, and some zinc may have existed as metal, but completely protected by a covering of copper. The reduction effected by the non-hydrogenised portions may also be due to hydrogen occluded during their preparation, but we cannot speak with certainty about it, in consequence of the possible presence of metallic zinc. There can be no doubt, however, that the finely divided copper of our couple does condense hydrogen, and when in this condition reduces nihe to nitrite and ammonia.Two facts which appeared difficult to reconcile, now appear intelli- gible enough: the one, that the couple reduces the chlorate in the cold without the least escape of hydrogen; the other, that in the ordinary electrolysis of the chlorate, nearly the whole of this gas escapes without reducing the salt. The reason is obvious. I n the first case the hydrogen is probably wholly occluded the moment it is set free, while in the other, only a small quantity of the gas is con- densed by the negative plate. Taking into consideration all the facts brought out by this inquiry, we consider it proved that-150 GLADSTONE: BND TRIBE ON THE ACTION, ETC. Time. NH3. 1 NH,N02. 1 Equil:lcnt PITHdKO3. a. The action of the copper-zinc couple on these oxy-salts is of an electrolytic nature.b. The negative radicle combines with the zinc, whilst the positive radicle, or its equivalent of hydrogen from decomposed water, is set free against the copper crystals. c . The reduction and hydrogenisation of the salt take place in the immediate vicinity of the negative metal. We also think it probable that hydrogen is actually set free against the copper, but is condensed by the finely divided metal, and in that condition does its work of reduction and hydrogenisation. Of course the resulting zinc compouiid and the alkaline hydrate decompose one another, producing the original salt and zinc hydrate. Work done each hour expressed in milligrams of IIy drogen. It may be assumed that this action of the couple is a general one, true not only of nitre, but of all nitrates containing metals which de- compose water a t the ordinary temperature.Animonium nitrate, though not strictly belonging to this class of bodies, should, according to what is known of the electrolysis of ammonium salts, and to the views just enunciated, give off a fourth of the hydrogen in its positive radicle when its solution is subjected to the action of the couple ; and since it is very probable that the real reducer in these actions is hydrogen, it naturally occurred to us that this salt ought not to form an exception to the above generalisation. But t o place the matter beyond doubt, we instituted a few additional experiments. A qualitative experiment with the couple showed at once that both nitrite and ammonia were produced, but not hyponitrite. We give the details of a quantitative trial:-410 C.C. of about 1.2 per cent. solution of ammonium nitrate were added to the usual quan- tity of couple (temp. 15" C.), and the ammonia and nitrate estimated. Subjoined are the results reckoned for 100 parts of solution :- 1 hour. ......... 4 hours ........ 11 . . . . . . . . . . 23 . . . . . . . . . . 0 -039 0 9209 0 -4445 0.114 1 0.185 0 -767 0 -179 0-159 1.04 I 0'2443 1 Xi1 1 -143 I---- -------- 100 45 * 5 16.4 7.8 The action of heat on a solution of ammonium nitrite resolves it, as is well known, into nitrogen and water, from which it was inferredWRIGHT AXD LUFF OS THE ALKALOIDS, ETC. 151 that were this reduction attempted a t or near the boiling point of the solution of the nitrate, the nitrite as quickly as produced would be decomposed in like manner. On trial, gas was evolved, but this proved to be mainly nitric oxide, which gas Thorpe had noticed on boiling solution of ammonium nitrate with the couple (Chenz,. Xoc. JournaZ, 187% p. 544). The amoitnt of this oxide of nitrogen we found in- creased with the strength of the nitrate solution. Thus with strengths of 20, 10 and 5 per cent. and an excess of couple, the nit,ric oxide was 8.5, 6 and 3 respectively. I n the cold the nitrate, even in solution of 20 per cent., was completely reduced to ammonia in about 24 hours without the escape of nitrogen free or combined. We might suggest therefore that, in estimating unlinown nibrates by T horpe’s process, it would be well to allow the couple to remain in contact with the nitrate solution for a t least 24 hours prior to distillation.

ISSN:0368-1645    

DOI:10.1039/CT8783300139

出版商:RSC    

年代:1878

数据来源: RSC

摘要:

WRIGHT AXD LUFF OS THE ALKALOIDS, ETC. 151 XIX. The dlkalods of the Aconites. Part 11. On the Alkaloids con- tained in Aconitum Feroz. By C. R. ALDER WRIGHT, D.Sc., Lecturer on Chemistry, and A. P. LUFF, Demonstrator of Chemistry, in St. Mary's Hospital Medical School. 8 1. Composition of Pseudacoizitine. FOR some years it has been known that the mixtures of alkalo'ids ex- t,racted commercially from A. NapeZZus and A, ferox are not at all identical, and it has been shown by von Schroff, T. B. Groves, and others, that the approximately pure alkalo'ids isolated from the two species, and purified by crystallisation from ether, alcohol, &c., differ in this respect, that whilst the N~peZZus base yields well cryatallised salts with facility, that from A. feroz does not form any kind of crys- tallisable salt at all (as shown below, we have found that there are exceptions to this rule), Accordingly, the terms aconitine and pseudaconitine have been employed t o designate the two alkalolds.These two substances have probably baen confused together by most of the older experimenters on the aconite alkaloids, who moreover did not obtain the crystallisable bases free from uncrystallisable alkalo'ids accompanying them (or formed from them by decomposition during extraction ?). The results detailed in Part I of these researches (this JowfiaZ, 1877, i, 143) tend to show that the crystallisable physiologically active base152 WRIGHT AND LUFF ON THE of A. Nayellus is a uniform homogeneous alkalond indicated, when per- fectly pure (to obtain which condition is a matter of some difficulty), by the formula C33HA3N0,2 ; for the perfectly pure base isolated from several specimens of roots exhibited exactly the same properties, and gave identical numbers agreeing well with this formula.Further ex- periments, which will be given in detail in a future paper, show that under certain conditions this base readily loses the elements of water, forming a well crystallised anhydro-derivative, closely resembling the parent base ; the somewhat irregular numbers obtained with different specimens of aconitine nearly, but not perfectly purified, are probably in many cases due to varying admixture of this derivative (produced during the process of extraction) with the unaltered aconitine. When subjected to the action of saponifying agents, it breaks up in accord- ance with the equation- forming belzzoic acid and a new alkaloid.The crystallisable physio- logically active base of A. fwox is in many respects very similar to aconitine. Like that base, it forms a derivative closely resembling the parent alkalo?d, by loss of the elements of water ; and the presence of this derivative, formed during the process of extract'ion, in the base obtained from the roots can, under certain conditions, be recognised : the action of sapoiiifying agents, however, sharply distinguishes the A . ferox base, pseudnconitine, from the aconitine of A. NapeZlzcs : for it splits up, by a reaction parallel t o the above, forming an acid identified as d i ~ e t h y ~ r o t o c a t e c h u i c acid, C6H3 O.CH, , together with a new alkalo'id altogether different from that produced in like manner from aconihe.In Part I it was incidentally stated that pseudaconitine is repre- sent,ed by the formula C3sH,,NOll : since these earlier experiments were made, we have found that the base then examined was not wholly pure, as it contained an admixture of the anhydro-derivative, upopseud- aco?zitiue, above referred to : pseudaconitine, when perfectly pure, is represented by the formula, C36H49N012, apopseudaconitine being formed from it by the reaction, COOH {0CH3 The specimen of alkaloi'd from which these earlier results were obtained was prepared by Mr. T. B. Groves (Year-book o j Pharmacy, 1873, 500) by exhausting the powdered roots with methylated spirit acidulated with hydrochloric acid in the proportions of 2 drachms to the gallon (1 in 640 by volume, corresponding to about 0.06 per cent.byALKALOIDS OF THE ACONITES. 153 weight of anhydrous HCl), evaporating to a small bnlk, aud extract- ing alkaloids by means of ammonia and ether, the ethereal solution being allowed to evaporate spontaneously, and the crystals thus formed separated from noncrystalline matter by filtration, pressure and crys- tallisation from alcohol. Owing to accidental circumstances, how- ever, some six or seven weeks elapsed between the concentration of the alcoholic extract to a small bulk and the further treatment of the con- centrated liquid ; probably this circumstance (or perhaps some over- heating during evaporation, &c.) was the cause of the partial dehy- dration of the pseudaconitine ; for other batches of roots worked up by Messrs.Hopkin and Williams (with the sole difference that 30 grains of strong sulphuric acid were used per gallon of alcohol instead of 120 of aqueous hydrochloric acid, which is not far from the same proportion of actual anhydrous acid) yielded, as described below, an alkalo'id which had not been noticeably dehydrated at all ; whilst the results detailed in Ej 4 show that contact with excess of dilute hydro- chloric acid at 100" for some hours suffices entirely to convert psenda- conitine into apopseudaconitine. The following numbers were obtained :- (A). Crystallised base as received from Mr. Groves dissolved in a rnixtu1.e of alcohol and ether, and recovered by spontaneous evaporation :- 0.3165 gram dried at 100" gave 0.7410 CO, and 0.2180 H20.0.8090 gram gold-salt gave 0.1575 Au. (B). Second crop of crystals regained from mother-liquors of A by further spontaneous evaporation :- 0.2925 gram dried at 100" gave 0.6805 CO, and 0.1970 H,O. 1.3260 gram gold-salt gave 0.2565 Au. 0.5730 gram of base burnt with soda-lime gave 0.0845 Pt. Calculated for Found. C36H49N012. C3RK7NOll. A. B. Carbon in base.. . . 62.88 64.38 63.84 63-45 Hydrogen ?, .. .. 7-13 7-03 7.65 7.48 Nitrogen ,, . . . . 2.04 2.09 - 2.09 Gold in gold-salt . . 19-10 19.44 19.46 19.34 Manifestly these numbers agree well with mixtures of pseudaconi- tine and apopseudaconitine, the latter being contained in larger proportion in Specimen 4, as might be expected from its somewhat less solubility i i i alcohol and ether (vide § 4).Another sample of pseudaconitine prepared by Mr. Groves from a different batch of roots, and purified not only by numerous crystal- lisations, but also by conversion into mercuriodide and regeneration VOL. XXYIII. N154 WRIGHT AND LUFF ON THE therefrom, gave numbers closely accordant with the formula C,,H,,NO 12- 0.3540 gram gave 0.8140 GO2, and 0.2410 H,O. 0.3195 gram gave 0.7365 CO,, and 0.2200 H,O. Calculated for C,,H,J012. Found. Carbon .......... 62-88 62.71 62.87 Hydrogen.. ...... 7.13 7.57 7-65 Unfortunately this specimen was too small in quantity for any extended examination. In order to subject pseudaconitine to a thorough examination several ounces were purchased of the rough alkaloid extracted from A.ferox roots by DiIessrs. H o p k i n and Williams by percolation with alcohol acidulated with sulphuric acid in the proportion of 30 grains to the gallon (about 0.05 per cent. by weight) ; from this the crystallised base was prepared by dissolving in ether, filtering from a little undissolved matter, and allowing to evaporate spon- taneously after admixture with about half its bulk of “ light petroleum distillate ” (that portion of the ‘‘ benzoline ” of the oil-shops which dis- tilled off in a water-bath). A large crop of crystals mixed with a, little resinous matter was thus obtained, from which the crystals were sept-Lrated by stirring up with a little alcohol (which dissolved the resinous matter with some of the crystals) and filter-pumping. These crystals were again crystallised from e ther-petroleum, furnishing a crop of apparently homogeneous crystals (1).To see whether these consisted of the pure base they were purified by solution in hot alcohol, addition of hot water till a milkiness appeared, clearing up by addition of a few drops of alcohol, a n d slow cooling ; white cauli- flower-like crystals thus formed (2). Another portion of crystals (1) were crystallised four times more from ether-petroleum (3). From these three specimens the following numbers were obtaioed :- Specimen (1). Specimen (2). 0.3225 gram gave 0.7465 CO, and 0.2135 H,O. 0.3840 gram gold-salt gave 0.0750 Au. 0.9395 gram gave 0..5540 GO, and 0.1610 H,O. 0.5105 gram burnt with soda-lime gave 0.0765 Pt. 0.704-5 gold-salt gave 0.1385 Au.0.2380 gram gave 0.5460 CO, and 0.1580 H20. 0-3025 gram gold-salt gave 0.0590 Au. Calculatrd for Found. Specimen (3). C36H,,NOU. (1 .) (31.1 (3 .> Carbon ............ 62.88 63.11 63.09 62.57 Hydrogen ........ ’7.1 3 7.36 7.47 7.37 Nitrogen.. ........ 2.04 - 2.12 - Gold in An-salt .... 19.10 1 9 5 3 19.66 19.50ALKALOIDS OF THE ACOKITES. 155 It is evident from these numbers that the crystallised base thus obtained was essentially pseudaconitine, but the high percentage of gold found in the gold-salt seems to indicate that (just as with aconitine, Part I), mere crystallisation of the free base from ether, alcohol, &c., does not suffice to free it entirely from accompanying substances ; a circumstance clearly proved by the following numbers obtained with base purified by conversion into recrystallised nitrate, regeneration, and crystallisation from ether-petroleum.Specimen A.-Nitrate prepared from the crude material supplied by Messrs. Hopkin and Williams; crystals of the salt were prepared by rubbing in a mortar the rough nlkalo'id with enough dilute nitric acid t o dissolve it, adding a few drops of concentrated nitric acid, and vigorously rubbing for some time, whereby a thick magma of crystals was formed ; this was drained on the filter-pump, washed with weak nitric acid, dissolved in warm water, and made to crystallise again by addition of a few drops of concentrated nitric acid, and stirring. The crystals thus obtained were perfectly white after filter-pumping and washing with dilute nitric acid ; they were again crystallised in the same way, and then decomposed by dissolving in water, adding sodium carbonate and shaking with ether ; the base which crystallised fyom the ether on spontaneous evaporation was washed with a little alcohol on the pump-filter, and then constituted a snow-white crystdine mass :- 0.2775 gram dried at lob" gave 0.6400 CO, and 0.1845 H,O.0.2920 gram dried in a current of air at 80" gave 0.6700 CO, and 0.5015 gram gold-salt gave 0.0970 Au. Specimen B.-Similarly prepared, the purified alkaloid recrystallised from ether and petroleum several times (Specimen 3, supTa) being employed in the first instance instead of the impure base obtained from Messrs. Hopkin and Williams. 0.1980 H,O. 0.2880 gram dried a t 100" gave 0*6630 CO, and 0.1920 H20.0.5655 gram gold-salt gave 0.1085 Au. 0.3090 gold-salt gave 0.0592 du. PO230 gram of base dried at 100" gave by vacuum-combustion Specimen 0.-The preceding sample of base, B, again converted 0.2750 gram dried at 100" gave 0.1845 H,O and 0.6330 GOz. 0.4640 gram burnt with soda-lime gave by titration of the evolved ammonia 0.00945 gram N ; by conversion into platinum salt, 0.0695 Pt. process 0.000473 gram nitrogen. into nitrate, recrystallised, and regenerated from the salt :- 0.5550 gram gold-salt gave 0.1070 An. N 2156 WRIGHT AND LUFF OK THE Fouii d . A. B. C. Calculatcd. ,----- 7 Mean. C,, ...... 432 62.88 62-90 62.57 62.59 62.77 62.71 Hi, ...... 49 7-13 7-39 7.53 7.41 7.45 7.44 N . . ...... 14 2.04 - - 2.06 2.03 2.12 2-07 01, - - ...... 192 27.95 - -- - - - Calculated for Found.C3,H,SN0,2,HCI,AuCl,. A. B. C. Mean. Gold = 19-10 19.34 19-18 19.16 19.28 1924 - The determination of the nitrogen in B was made by combustion with oxide of copper and metallic copper in a Sprengel vacuum. 0.0230 gram of base thus gave 27-95 C.C. of GO2, and 0.377 of N a t 0" and 760 mm. (corrected by subtracting the minute amounts of each gas obtained in a blank experiment made simultaneously), or 0.0150 gram carbon, and 0.000473,of nitrogen. These values give 65.2 per cent. of carbon, somewhat too high, but not more so than the experimental errors might account for ; the volume ratio of N to GO, is 0.377 - 1 1 'L7.y5 - - - - 74.2, giving the ''atom "- ratio -, the calculated ratio 37 1 1 being 36- Pseudaconitine is far more readily soluble in alcohol and ether than aconitine ; when crystallised from ether, or, better, ether and petro- leum spirit, it f o r m transparent needles and sandy crystals ; but if the evaporation be not extremely slow, and especially from alcoholic solu- tions, it is apt t o separate as a varnish at the upper edge of the solution, soon becoming a confused mass of milk-white cauliflower-like crystal- line efflorescence : the crystals, when air-dry, are hydrated, the water of crystallisation being lost a t 80" in a current of dry air without any fcsion or fritting ; if heated to loo", the hydrated crystals lose their water with fritting more or less marked (the anhydrous base also frits a t looo, but less quickly).Crystals from Specimen No. 3 of base purified by several cry stallisations from etber-petro- leum ; 0.6640 gram of air-dry crystals lost a t 100" 0.0175.......................... = 2-65 per cent. Crystals from base purified by conversion into nitrate and regeneration (Specimen Aszqwa) ; 1.2770 gram lost a t 80" in a current of dry air 04360 ............................ = 2.82 ,,ALKALOIDS OF THE ACONITES. 157 Base from nitrate (Specimen C supra) ; 1,0020 gram lost at 100" 090270 ................ = 2.69 per cent. Calculated for C36H19N012,Hz0. ..... = 2.55 .. The salts of psendaconitine, for the most part, are so extremely diffi- cult to crystallise that hitherto they have only been obtained as varnishes by spontaneous evaporation ; the kind of treatment above described, which yielded a crystallised nitrate, did not answer with the snlphate, hydrochloride, acetate, oxalate, &c.If the alkaloyd be dissolved in just sufficient dilute warm nitric acid t o form a nearly neutral salt, the liquid generally dries up t o a varnish without crystal- lising ; if, however, a crystal of nitrate be placed in the liquid and the whole well stirred, the dissolved salt gradually separates in crystals : crystallisation takes place, however, with far greater facility on adding a few drops of concentrated nitric acid and stirring vigorously. The following numbers were obtained with a specimen of the salt r e c r p tallised from a nearly neutral aqueous liqclid :- 0.7920 gram of air-dry salt Iost at 100" 0.0570 = 7.19 per cent. 0.2680 gram of dry substance gave 0.5740 GO, and 0.1805 H20.Calculated for C36H4,N0,2,HN03,3H20 = 6.72 ,, Calculated. Found. Carbon .......... 57.60 58.39 Hydrogen ........ 6.67 7-48 The condensed water was strongly acid, as might have been expected in the combustion of a nitrate; whence also the high value for the carbon found. The gold-salt of pseudaconitine is distinctly crystalline when pre- cipitated from a dilute solution : after drying over sulphuric acid it can be readily crystallised from boiling alcohol in minute needles only sparingly soluble in cold alcohol : when air-dry the crystals are an- hydrous. The following combustions of different specimens of gold- salt were made, the high percentage of carbon found being apparently due to the escape of a minute quantit>y of chlorine liberated on heat- ing the gold-salt ; for the condensed water contained chlorine, and strongly acted on iodide and starch-paper.(A) Gold-salt prepared from base only purified by repeated crystal- lisation from ether-petroleum- (B) Another sample similarly prepared- 0,3215 gram gave 0.5025 CO, and 0.154,5 H,O. 0.2'330 gram gave 0.4600 COs and 0.1410 H,O.158 WRIGHT AND LUFF ON THE (C) Prepared from base regenerated from nitrate- (D) Another specimen similarly prepared- 0.4660 gram gave 0.7280 GO, and 0.2205 H,O. 0.3250 gram gave 0.5125 CO, and 0.1560 H,O. C~~H,SNOI.?,HCI,-~UCI~. A. B. C. D. Carbon . . . . 42.11 412.61 42-82 42.60 42-99 Hydrogen .. 4.87 5.34 5.35 5.25 5.33 Calculated for Found. Although crystallisalde, the auro-chloride does not seem t o be as well suited for the final purification of the nearly pure base as is the nitrate ; a sample of salt prepared from the nearly pure base crystal- lised several times from ether-petroleum (Specimen (3) supm), and containing originally 19.50 per cent.of gold was recrystallised from boiling alcohol: the crystals dried over sulphuric acid and finally a t 100" were not perceptibly altered; 0.8095 gram gave 0.1575 Au = 19.47 per cent. On the other hand, as above stated, when the same sample of base was converted into nitrate, recrystallised, and the base regenerated, the gold-salt finally obtained contained 19.18 and 19.16 per cent. Au (Specimen 13, szq~ra), the theoretical value being 19.10. It is noteworthy that just the same thing is observable with aconitine, no diminution in porcentage of gold being noticeable on crystallising from alcohol the gold-salt (prepared from the alkaloid cryatallisecl from ether, &c., only), whilst as shown in Part I, a diminution of 0-2 to 0-3 per cent.is brought about by conversion into hydrobromide and i*ecrystallising and regenerating the base, the pure alkalo'i d thus ob- tained furnishing a gold-salt containing the theoretical percentage of gold, whilst the original approximately pure base contained too high an amount by 0.2 to 0.3 per cent. The mercuriodide of pseudaconitine prepared by precipitating R solution of tbe base in acetic acid by potassium mercuriodide, is an amorphous, flocculent, white precipitate, very sparingly soluble in water : after washing and drying at 100'- 0.5510 gram gave 0.2970 AgI Calculated for C36H49N012,HI,Hg'12 ,, = 30.02 ,, Iodine = 29.12 per cent. Pseudaconitine is sparingly soluble in water and in fixed caustic alkalis, somewhat more readily in ammonia and sodium carbonate ; from the latter solution, if saturated, it can be regained in an impure state (owing to incipient saponification) by quickly evaporating, when the alkaloyd separates as a resinous film which yields crystals on solu- tion in ether, addition of petroleum spirit, and spontaneous evapora- tion, if it have not been too long exposed to the action of the hot : lkaline fluid.I n its qualitative reactions it closely resembIes aconi-ALKALOIDS OF THE ACONITES. 159 tine, being precipitated by mercuric chloride (precipitate redissolved on moderately large dilution) ; potassium mercurobromide (precipitale only sparingly soluble on adding water) ; potassium mercuriodide (precipitate 1-ery sparingly soluble) ; tannin ; iodine dissolved in potas- sium iodide ; gold chloride ; caustic potash, soda, and ammonia ; sodium carbonate, &c.; the precipitates being more or less readily dissolved on largely diluting with water.Platinic chloride only forms a precipitate in concentrated solutions, the salt being pretty readily soluble in water and also in alcohol. From aconitine pseudaconitine differs sharply in molecular weight, and in solubility in alcohol and ether ; also in crystallising with H,O (aconitine crystallises anhydrous, Part I) ; and more especially in melting point : as stated above pseu- daconitine slightly frits a t 100"; in a capillary tube it melts to an extremely viscid, transparent fluid a t about 104-105", the exact point of fusion not being very distinctly marked ; whilst pure aconitine first melts completely at 189" (corrected), a slight fritting and browning being noticeable a few degrees below the melting point.As shown below, the action of saponifying agents on pseudaconitine gives rise to dimethyl protocatechuic acid ; whilst under the same conditions, as will be shown in a future paper, aconitinc gives rise to bcnzoic acid. Pseudaconitine can be heated to 105" for some hoiirs without mate- rially da,rkenirig in colour or losing in weight (if deprived of its water of' crystallisation previously) : at somewhat higher temperatures, how- ever, it turns yellowish, and then brownish, and finally dark chestnut, losing in weight several per cents.The loss of weight, however, ap- pears to be due, a t least in part, to the removal of substances other than water, as the increase in carbon percentage does not correspond t o that due to the loss of weight, assuming water only to be removed: thus, after four hours' heating to 135", 8-38 per cent. in weight was lost, but the chestnut-coloured varnish produced contained carbon 64.30, hydrogen 7-22; had the 8-38 per cent. lost been due to the removal of water only, the percentages should have been-carbon, 68.63 ; hydrogen, 6.77. The varnish, when dissolved in tartaric acid and precipitated by sodium carbonate, yielded a base soluble in ether with brown flakes not dissolved by that menstruum ; the ethereal solu- tion furnished, by spontaneous evaporation, only a nearly colourless varnish from which no crystals or crystallised salts could be obtained : this amorphous alkaloid contained carbon, 65-51 ; hydrogen, 7-50, whilst the composition, 2CXHi9NOL2-3Hz0, would require-carbon, 65.45 ; hydrogen, 6.97.A precisely similar substance was obtained in an experiment made with a view to see if pseudxconitine resembles quinine and cinchonine in the formation of an isomeride by heating the acetate: acetate of pseudaconitine was heated to 130-140" for an hour, and the somewhat ccloured mass dissolved in aqueous t.a.rtaric160 VRIGIHT AND LUFF ON THE acid and treated with sodium carbonate and ether : the residue left on spontaneous evaporakion of the ethereal solution would not yield crys- tals nor crystalline salts ; it contained carbon, 66.27 ; hydrogen, 8.2$, the composition, C36H49N012-2H20, requiring-carbon, 66.36 ; hydro- gen, 6.91.§ 3. Action of Alkalis o n Psezcdaconitine. When pseudaconitine is heated to 100" in sealed tubes wit,h alcoholic soda for 12 hours or more, it becomes completely broken up, with as- similation of the elements of water, into dimethyl protocatechuic acid and a new base, to which it is proposed to apply the term Pseudnco- nine ; thus- A small quantity of a yellowish resinous bye-product of feebly acid character is also formed by the further action of the alkali on the pseudaconine, but the amount of colouring-matter produced is but small. If, instead of allowing the reaction to take place in a sealed tube, a boiling alcoholic solution of soda be employed, an inverted condenser being attached, complete saponification is also brought about in less than 24 hours, but the amount of resinona bye-product is increased; on the other hand it is diminished if, in the sealed tube, the air be displaced by coal-gas before closing the tube.Thus the follow- ing values were obtained, the dimethyl protocatechuic acid formed being extracted by evaporating off the alcohol from the product of the reaction, and trea,ting the residue with hydrochloric acid and ether ; three agitations of the acidified aqueous fluid with about its on-n bulk of ether were found to remove completely the dimethyl protocatechuic acid, which was obtained in a weighable form by simply allowing the ethereal extract to evaporate spontaneously and drying the residue at 100'.As the residue thus obtained contained small quantities of feebly acid resinous amber-coloured bye-product, its alkali-saturating power was carefully determined with decinormal soda solution : the percent- ages of acid calculated from the weight of the residue and from the soda neutralised in three experiments were as follows :- (A) 1.0720 gram of pure anhydrous psendaconitine heated to 100" for 24 hours with alcoliolic soda in a tubc from which the air had been displaced by coal-gas before sealing up. Residue dried at 100", weighed 0.3060 gram: soda solution neutralised cor- responded to 0.2917 gram of the monobasic acid, C9H,,Oa. (B) 1.3105 gram similarly treated, save that the air was not dis- placed by coal-gas.Residue weighed 0.3860 ; soda solution neutrnlised was eqiiivalent to 0.3733 gram C,HI0O4.ALEALOIDS OF THE ACONITES. 161 (C) 1.3730 gram boiled with alcoholic soda 24 hours. Residue weighed 0.4440 gram : soda neutralised was equivalent to 0,4372 gram CgH1004. Calculated for above equation. 26.49 Percentage of C,H,,O4 obtained from C36H49N012. ... Found. A. B. C. From weight of residue .......... 28.54 29.45 32.34 From result of titration .......... 27.21 28.48 31.84 The coloured resinous feebly acid bye-product was present in sensibly larger quantity in €3 than in A, and to a considerably larger amount still in C : whence it is evident that the amounts of pure dimethyl protocatechuic acid actually formed in these experiments were very close to the theoretical quantity, t.he higher numbers obtained above being manifestly due to the increasing amount of this bye-product.The complementary product, C27H4,NOg, pseudaconine, formed in these three experiments, did not contain any undecomposed pseudaconitine, as on subjecting it to a second saponification no dimethyl protocate- chuic acid at all was formed, although the resinous bye-product was produced in small quantity. The dimethyl protocatechuic acid thus obtained dissolved in boiling water, leaving behind a minute amount of resinous matter ; on cooling i t crystallised out in anhydrous needles. After recrystallisation from boiling water two different specimens (one derived from Mr. Grove's batch of alkalo'id (9 l), and the other from Messrs.Hopkin and Williams' batch) melted respectively at 176-177" and 177-178" (corrected). On fusion with caustic potash at 250", acidifying the " melt," and shaking with ether, protocatechuic acid was abundantly formed, easily identified by its peculiar colour-reactions with ferric chloride, &o. 0.2325 gram gave 0.5030 CO, and 0.1175 HzO. C g . . . . . . . . . . . . . . 108 59.34 59.01 H,, ............ 10 5-49 5.62 0 4 .............. 64 35.1 7 On analysis the following numbers were obtained :- Calculated. Found. - ~~ ~ CgH1oOa ........ 182 100.00 The melting point, physical properties, and qualitative reactions (especially the formation of a gelatinous silver-salt on the addition of silver nitrate t o the neutral ammonia-salt) of this substance exactly agreed with synthetically prepared dimethyl protocatechnic acid ; Beckett and Alder-Wright, however, found (this JozmzaZ, 1876, i,162 WRIGHT AND LUFF ON THE 304) that the latter crystallised with H,O : on the other hand, Koelle describes synthetically prepared dimethyl-protocatechuic acid as an- hydrous (Liebig's AmaZen, clix, 240), as is also that prepared by the oxidation of methyl-eugenol (Graebe and Borgmann, ibld., clviii, 282) ; the acid from pseudaconitine crystallised anhydrous both from boiling water and from ether containing water.* Attempts yet further to identify this acid as dimethyl protocatechuic acid by distilling it with soda-lime led to but little result on account of the minute yield: Koelle obtained (Zoc.cit.) dimethyl-pyrocnte- chin (in an impure state) by the reaction- CO.0H C6H3 O.CH, { O.CH, the yield being not more than 5 per cent.: we obtained a small quantity of an oil resembling in appearance and odour the dimethyl pyrocate- chin obtained from hemipinic acid by similar treatment ( B e c k e t t and Alder-Wright, this JournnZ, 1876, i, 281) ; the quantity was too small to determine the boiling point, or to purify f o r combustion, but, on heating with amorphous phosphorus n"nd hydriodic acid to 100" for some time and shaking with ether, a substance was dissolved out readily soluble in water, and giving with ferric chloride the colour reaction of yyrocatechin : the original oily matter did not do this, SO that there can be no doubt that the oily body really was dimethyl pyrocatechin converted into pyrocatechin by the hydriodic acid as shown by B e c k e t t and Alder-Wright (Zoc.cit.), thus:- It is noteworthy that the mixture of pseudaconitine and apopseuda- conitine, crystallised from alcohol, and nearly but not quite pure, pre- pared by Mr. Groves ( 5 11, and also the crude alkalo'idal mixture, manufactiired by Messrs. H o p k i n and Williams, furnished on saponification an acid, from which minute amounts of benzoic acid were separalsle by distillation with a large bulk of water, dimethyl- protocatechuic acid not being thus carried over. By neutralising the distillate with soda, evaporating to a small bulk, acidifying, and shak- ing with ether, small quantities of benzoic acid were obtained, melting at 120- 121" in each instance.The pseudaconitine regenerated from * Since this paragraph was written it has been shown by K a e t a Ukimori &;I a t s mo t o (Deut. Chem. Ges. Ber., xi, 122) that dimethylprotocatechuic acid crptallises anhydrms from hot solutioils when the crystals form at a temperature above 50") and v-ith H,O from dilute solutions below 50"ALKALOIDS O F THE ACONITES. 163 the nitrate, after recrystallisation of that salt, however, did not furnish sensible quantities of benzoic acid by this mode of treatment. It has been stated abore, and will be demonstrated in a future paper! that benzoic acid is a product of the saponification of aconitine, whence it appears extremely probable that these two preparations contained small quantities of aconitine, removed by conversion iuto nitrate, and recrystallising.The amount of aconitine (if aconitine it were) thus present represented only about 0.5 per cent. of the total alkaloids in the case of the first substance, and 1 per cent. in the case of the second. Whether the base furnishing benzoic acid is a natural constituent of A.ferox, or whether it arose in the presen-i; instances from admixture of ft few roots of A . NapeZZus, or some other species containing aconitine, with the A . ferox roots, cannot be determined ; this latter is extremely probable, although the former is also very likely, the more so as we have found that the rough alkalo'idal matters obtained from the roots sold as A. NapeZlus furnish a little dimethylprotocatechuic acid on saponification along with much benzoic acid.Pseudaconine is obtainable in a state of considerable purity by ren- dering alkaline with sodium carbonate, and evaporating to dryness on the water-bath, the acid liquid obt'ained by saponifying pure pseudaco- nitine with alcoholic soda, and removing the dimethylprotocatechnic acid and resinous bye-product formed by shaking with ether. From the residue alcohol dissolves out pscudaconine, which can be purified by evaporating off the alcohol from the clear filtrate, and dissolving the residue in ether, in which it is readily soluble. On spontaneous eva3po- ration a clear, slightly yellow varnish, fusible in the water-bath, is obtained, pretty readily soluble in water, forming a solution of strongly alkaline reaction and bitter taste, n o t prodwing the slighfest lip tingZing.The following numbers were obtained with the varnish dried a t lOO", till constant in weight :- 0.2970 gram gave 0.2105 H,O and 0.6680 CO,. 0.2510 gram gave 0.1795 H20 and 0.5630 CO,. 0.9645 gram burnt with soda-lime gave by titration of the evolved ammonia 0.02533 gram N. Calculated. Found. C 2 7 .......... 324 61.95 61.34 61.17 HdI .......... 41 7.84 7.87 7-94 N ............ 14 2-67 2.62 O9 - .......... 144 27-54 C17H*,NO, .... 523 100.00 As yet it has not been found practicable to obtain pseudaconine164 WRIGHT AND LUFF OK THE in a ci*ystallised state in any quantity ; but if a thin film of the base be left on a watch-glass by evaporation of its ethereal solution, and set aside for some weeks, it gradually becomes converted into a mass of well defined acicular crystals a quarter of an inch in length.None of its salts have yet been obtained crystallised. Unlike pseudaconit'ine, pseudaconine can be heated to '120-130" for two hours, without losing in weight more than traces ; it darkens in colour somewhat by the treatment, however. At higher temperatures it probably loses water, forming an anhydro-derivative (vide § 3). The aqueous solution throws down a brown precipitate of silver hydrate from the nitrate, becoming black, a,nd evidently reduced on beating ; it reduces ammoniacal silver nitrate on boiling, and gold chloride in the cold on standing, but produces no appreciable reduction of cuprous oxide from F e h l i n g ' s solution, el-eri when boiled therewith for some time. It readily neu tralises acids, requiring quantities of titrated soh- tions, corresponding to the equivalent 523 ; the salts have as yet not been obtained otherwise than as varnishes, or scale-preparations.The hydrochloride throws down from gold chloride a yellow precipitate, which either decomposes whilst washing and drying, G r else contains reduced gold, as it exhibits no constant composition. Three different specimens contained 23.65, 25.41, and 25.85 per cent. of gold respec- tively, the formula, C2,H41N09,HC1,AuC13, requiring 22.74 per cent. ; an aqueous solution of the gold-salt deposited reduced gold on standing over sulphuric acid i n the dark. As a check on the molecular weight, the mercuriodide was prepared by dissolving the base in acetic acid, and adding potassium mer- curiodide ; it formed a white, amorphous precipitate, of which, after washing and drying over sulphuric acid, and finally at loo", 0.7240 gram gave 0.4650 AgI, and 0.1540 HgS.Calculated for C27H,,,N09,HI,HgI,. Found. Iodine ........ 34.48 39-71 Mercury.. ....... 18.10 18.31 In most of its qualitative reactions pseudaconine resembles pseuda- conitine, the precipitates being usually somewhat more soluble in water. Caustic potash in excess precipitates it from moderately con- centrated solutions, but not from dilute ones. Sodium carbonate does not precipitate saving from the most concentrated solutions, e.g., when a solution in excess of sodium carbonate is evaporated down until the salt begins to crystallise out ; the baae then partially separates as a fluid mass.AIJKALOIDS OF THE ACONITES.165 9 3. Action of XaponiJying Agents on PsezcdcLconiti?ie at Temperatures above 100". If the saponification of pseudaconitine with alcoholic soda be carried out a t a temperature of about 140", the ultimate products formed differ from those produced a t 100", in this respect, that the base comple- mentary to dimethylprotocatechuic acid contains the elements of H,O less than pseudaconine, and may therefore be termed apopseudacoruhe. In all probability this is formed by the removal of water from pseuda- conitine, forming apopseudaconitine (8 4), and the subsequent saponi- fication of the base thus produced. and not by the direct dehydration of pseudaconine ; for, as above stated ($ 2), pseudaconine is not perceptibly altered by heating to a tem- perature of about 130°, whilst pseudaconitine loses the elements of water a t a temperature considerably below this.I n general and physical properties apopseudaconine closely resenzbles pseudaconine, the only noticeable difference between them being the numbers given on combustion ; no marked increase in the amount of colouring matter and resinous bye-product appears to accompany the employment of the higher temperature for saponification ; on the other hand, if water alone be employed instead of alcoholic soda, sa,poni&a- tion is brought about a t 140", though not so rapidly as with the alkali, only about 85 per cent. of the pseudaconitine being decomposed in 24 hours ; the dimethylprotocatechuic acid thus produced is, how- ever, almost perfectly free from the colouring matter and resinous bye- product formed to a greater or lesser extent when alcoholic soda is used.Thus in two experiments, 22.15 and 22.8 per cent. of dimethylproto- catechnic acid were found (calculated, 26.49) after 24 hours' digestion at about 140" ; the alkalojid extracted from the product of the reaction, when obtained as a varnish by the evaporation of its ethereal solution, and digested with water, did not wholly dissolve, but left behind solid particles of altered pseudaconitine, which furnished dimethylproto- catechuic acid on further saponification ; on first moistening the resinous mass with water, it became white and opaque on the surface, and pre- sented the appearance (to the naked eye, not under the microscope) of a crystalline film ; this appearance is not presented by pure apopseuda- conine, freed from all traces of substances capable of saponification (pseudaconitine and the products of the action of heat thereon) by the action of alcoholic alkali. In a preliminai-y report t o the Pharma-166 WRIGHT AXD LUFF ON THE ceutical Conference (Yew-book of Pharmacy, 1877,444), this appearance was erroneously supposed to be characteristic of pseudaconine, which was then confounded with apopseudaconine, the exact formula of pseudaconitine not having at that time been arrived at, the method of purifying the base by conversion into crystallised nitrate not having then been found out.The following numbers were obtained :- A. Apopseudaconine obtained by the action of water at 140" for 24 hours- 02410 gram gave 0.5630 CO,, and 0.1815 H,O.0.2410 gram gave 0.5600 C02, and 0.1815 H,O. 0.2460 gram gave 0.5690 CO,, and 0.1860 H,O. B. Another specimen similarly obtained- C. Prepared by alcoholic soda at 140" for 24 hours- Fouii d . Calculated. A. B. C. C27 .......... 324 64.16 63.71 63.36 63.10 HS9 .......... 39 7-75? 8.37 8.37 8.40 N .......... 14 2.77 0 s .......... 128 25.35 - I - - L - C27H,,NOa .... 505 100.00 8 4. Action of Acids on Pseudaconiti.ne. When pseudaconitine is heated in contact with dilute or concentrated mineral acids, it quickly becomes saponified and altered, dimethylpro- tocatechuic acid being extractable by ether froni the prodnct of the action in larger or smaller quantity, according to circumstances ; the saponification, however, does not seem to be as rapid as a rule as with alkalies ; thus, solutions of pseudaconitine in cxcess of dilute hydro- chloric, nitric, or sulphuric acid may be allowed to stand for weeks in the cold, and even gently warmed for some time without the formation of more than traces of (and often of not any) dimethylprotocatechuic acid; whilst if a pseudaconitine salt be diluted with water, and an alkali added in excess, on standing for some time (a few hours to a few days) dimethylprotocatechuic acid is always formed to a con- siderable extent, even in the cold.On heatiiig to 100" a solution of pseudaconitine in excess of a mineral acid, saponification is brought about rapidly, especially with a concentrated acid ; thus about 40 per cent. of the alkali is saponified on heating to 100" for 3 hours, with about 10 parts of concentrated hydriodic acid.No methyliodide is thus formed, and no protocatechuic acid is obtained, showing thatALKALOIDS OF THE ACONITES. 167 the dimethylprotocatechuic acid generated is not demethylised at 100' by hydriodic acid. Hydrochloric, hydrobromic, and sulphuric acids produce analogous results ; the product of the continued boiling for some hours with dilute sulphuric acid does not reduce F e hling's solu- tion. Organic acids, however, such as tartaric and acetic, act very differently ; scarcely a perceptible trace of dimethylprotocatechuic acid is formed when pseudaconitine is heated to 100", with a large excess of glacial acetic acid, or of almost saturated solution of tartaric acid for several hours ; or even if boiled with moderately concentrated tar- taric acid solution for several hours.Other changes, however, are produced by these organic acids ; thus after 8 hours' heating t o loo", with nearly saturated solution of tartaric acid, the pseudaconitine becomes converted into qopezLducomXhe by the reaction- CJLNOi, = 8 2 0 + C J L N O i i . The product of the action was diluted with water and treated with cmstic soda and ether : from the ethereal solution there separated on spontaneous evaporation crystals of apopsendaconitine so closely re- sembling the original base that it is somewhat difficult to distinguish them ; apopseudaconitine, however, appears to be decidedly less ex- tremely soluble in alcohol and ether, although its solubility in these menstrua is still considerable.When anhydrous it slightly frits at 100" (like peeudaconitine) and melts t o a thick viscid mass at 103- 103", or slightly lower than pseudaconitine which fuses similarly at about 105" ; when the two are compared side by side, it is distinctly seen that apopseudaconitine melts some 2" below pseudaconitine. When crystallised from ether by spoiltaneons evaporation apopseuda- conitine is represented by the formula C3,H,,N0,,,H20 ; i e . , it is iso- meric with pseudaconitine deprived of its water of crystallisation : like the crystallised parent base it readily becomes anhydrous a t 100". 0.5645 gram of air-dry base lost a t 100" 0.0160 = 2.83 per cent. 0.2310 gram of base dried at 100" gave 0.5480C02 and 0.1685 H,O.The base furnishes a well-crystallised nitrate on rubbing with excess of dilute nitric acid, or on dissolving in sufficient dilute acid, adding a few drops of concentrated acid, and stirring vigorously. From the crystals of nitrate thus prepared the base was regenerated by means of soda and ether ; of the resulting substance, 0.2745 gram dried a t lij0" gave 0.6445 COz and 0.1925 H20. Calculated for C36HliNOll,H20 = 2.62 ,,168 WRIGHT AND LUFF ON THE Calculated. Found. c36 ........ 432 64-57 64.69 64.03 HJ, ........ 47 7-03 8.10 7-79 N .......... 14 2.09 O,, ........ 1'76 26.31 - - - - The gold-salt, when precipitated from weak solutions of the hydro- chloride, is crystalline ; when dried over sulphuric acid it can readily be crystallised from hot alcohol in minute anhydrous needles.0.3005 gram gave 0.0585 Au = 19.46 per cent. Calculated for C3GHB,N011,HC1,AuC13 = 19.44 ,, I n order to see if inorganic acids also cause the dehydration of pseudaconitine as well as its saponification, pure pseudaconitine was heated with about 15 parts of an aqueous solution containing 5 per cent. of HCl to 100" for 8 hours. On shaking the acid liquid with ether, dimethyl protocatechuic acid was dissolved out to an extent indi- cating that about a twentieth part of the pseudaconitine used had been saponified. On adding soda and ether, and allowing to evaporate spontaneously, crystals formed, less readily soliible in alcohol and ether than pseudttconitine, giving rise to a crystalline gold-salt and a well-crystallised nitrate : these crystals, however, were slightly mixed with a non-crystalline base (presumably pseitdaconine formed by the saponifhation) ; they mere converted into nitrate, filter-pumped and washed with weak nitric acid ; from the salt thus obtained the base was regenerated corresponding in all respects with the apopseudaconi- tine prepared by means of tartaric acid.0.2475 gram dried at 100" gave 0.5815 CO, and 0.1825 H,O. Calculated. Found. Carbon .......... 64.57 64.08 Hydrogen ........ 7.03 8-19 From these results there can be little doubt that the specimen of pseudaconitine prepared by Mr. G r o v e s by means of alcoholic hydro- chloric acid (§ I.) actually contained apopseudaconitine, formed by the action of the hydrochloric acid during the extraction. Glacial acetic acid acts in a somewhat different fashion from aqueous tartaric acid : the elements of water are indeed removed from pseud- aconitine, but the resulting apopseudaconitine is further acted on form- ing acetyl! apopseudaconitine in accordance with the reaction CJLNOii 1- C,H:,Q, = EL0 + CxHA,(C,H,O)NOII,ALKALOIDS OF TEIE ACONITES.169 just as morphine and codeine give rise to acetylated derivatives by similar treatment (Alder-Wright, this Journal, 1874, 1031). Pseudaconitine was heated to 100' for 8 hours with about 12 parts of glacial acetic acid : on diluting the resulting fluid with water, adding soda and agitating with ether, and allowing the ethereal solution to evaporate spontaneously, a well-crystallised base was obtained sensibly less soluble in alcohol and especially in ether than pseudaconitine, though still readily soluble in either menstruum.When air-dry it contains one proportion of water of crystallisation (like pseudaconi- tine and apopseudaconitine) . 0.4955 gram of air-dry crystals lost at 100" 0.0130 gram ............................ = 2.62 per cent. Calculated for C,,H46(C,H,0)No,,,H,0. . = 2.47 ,, 0.2575 p m . of base dried at 100" gave 0.6080 GO2 and 0,1850 H20. Calculated. Found. C, .................... 456 64-13 64.38 H4g .................. 49 6.90 7.9 8 N .................... 14 1.97 OI2 .................. 192 27-00 - CS~H~~(C~H,O)NO~I .... 711 1OO.00 In order to determine the degree of acetylation, 0.5970 gram of anhy- drous base were dissolved in alcohol, exactly neutralised, and saponified in a soda-water bottle (at 100" for about 14 hours) with a measured excess of standard caustic soda solution.From the amount of soda neutralised the quantity of mixed acetic and dimethylprotocatechuic acids formed was calculated, being 0.2057 gram of a mixture of equi- valent quantities of CgH1,04 and C2H402. The whole was then acidi- fied and the acetic acid distilled off with water as long as any acid came over: by titration the distillate was found to contain 0.0510 gram of C2H4O2. Finally the dimethyl protocatechuic acid (and a trace of resinous decomposition-product) was extracted from the residue in the distillation-flask by means of ether, and the ethereal solution evaporated to dryness and weighed after drying at 100" : the residue weighed 0.1590 gram, and when titrated by standard soda neutralised alkali equivalent to 0.1550 gram of CyHL004. Found.Calculated. By titretion. By weighing. Acetic acid. ................. 8.44 8-53 - - Dimethyl-protocatechuic acid . . 25-59 25.96 - 26.63 Total acid .................. 34.03 34.51 34.46 Acetyl apopsendaconitine forms a well-crystallised nitrate on stir- ring with excess of dilute nitric acid: the gold-salt is thrown down VOL. XXXIII. 0170 WRIGHT AND LUFF ON THE in microscopic crystals from a dilute solution of the hydrochIoricle on adding auric chloride; it is readily crystallisable from hot alcohol, and is but sparingly soluble in cold alcohol. The anhydrous base melts at a somewhat higher temperature than pseudaconitine in a capil- lary tube, becoming a highly viscid transparent mass at about 115", the melting point, like that of pseudaconitine, not being very distinctly marked: it slightly frits at lOO", however, on heating for some time.6 5. Actiort of Organic Anhydrides on Psedaconitine a?Ld Pseudnconiwe. It has been shown by one of us (this Journal, 1874, 1031), that whilst morphine furnishes, when treated with glacial acetic acid, an acetyl derivative containing only one acetyl group per 1 nitrogen symbol in the formula, it gives rise, by the action of acetic anhydride in excess, to a derivative containing twice as many acetyl-groups. In order to see if pseudaconitine behaves in a similar way, the anhydrous base was heated to 100" for an hour with twice its weight of acetic anhydride : to the colourless product a dilute solution of tartaric acid was added and the whole agitated with ether to remove any trace of resinoid bye-product.Soda was then added to the aqueous liquid and the whole agitated with ether. By spontaneous evaporation, crys- tals were obtained which on examination proved to be i d e l h h l wiih t h e ncetyl apopseudaconitiize formed by the action of glacial acetic acid (§ 4), and not a more highly acetylated product : it melted at 113" ; after drying at 100" 0.2615 gram gave 0.6180 CO, and 0.1875 H20. Calculated. Found. C38 .................. 456 64-13 64.45 Hdg .................. 49 6-90 7-96 N.. .................. 14 1.9 7 012 .................. 192 27.00 - - On saponification, 0.7800 gram neatralised soda equivalent to 0.2710 gram of CgH,,O, + C,H40,. On distilling off the acetic acid formed and titration, 0.0'740 gram C2H402 were obtained: from the residue by means of ether there was extracted 0.19'70 gram of crude dimethyl protocatechuic acid, which on titration neutralised soda equivalent to 0.1965 gram C9HloOl. Acetic acid.................. 8.44 9.48 - - Dimethyl protocatechuic acid.. 25.59 25.19 - 25.26 Found. Calculated. By titration. By weighing. Total acid .................. 34.03 34.67 34.74ALKALOIDS OF THE ACONITES. 171 Hence the action of acetic anhydride on pseudaconitine is represented by the equation- C36H19N012 + 2( C2H30)20 = 3C2&Oz + C36H46(CZH3O)NO11. Benzoic anhydi-ide yields precisely similar results, benzoyl-apopseud- nconitine, C3sH4,( C7H50)NO11, being formed when benzoic anhydride is made to act on pseudaconitine, the reaction being- C3JLNO12 + 2 (C,H,O)zO = 3C7H.502 + C ~ ~ H ~ ~ ( C ~ H ~ ~ ) N O I I Anhydrous pseudaconitine was mixed with twice its weight of benzoic anhydride and heated for two or three minutes to about 120" to render the whole fluid, the liquid being then kept at 1OOOfor from one to two hours. On cooling and standing, the whole solidified to a crystalline mass (containing much benzoic acid) : this was dissolved in a mini- mum of alcohol and largely diluted with ether, enough dilute solution of caustic potash added to set free any base present, and the whole well agitated and allowed to stand.The supernatant ethereal solu- tion of new base, together with undecomposed benzoic anhydride and resinous bye-products (formed only in very small quantity), was then separated and agitated with dilute tartaric acid solution ; and from the purified tartrate thus obtained, the base was regenerated by means of alkali and ether.On spontaneous evaporation, the ether left an indis- t,inctly crystalline residue, which did not crystalliss well on adding a few drops of alcohol and allowing to stand, but which was the hydrate of the benzoylated base, benzoyl-apopseudaconitine, CB6H46( CiH5O)NOll, H2O. 0.2730 gram of air-dry substance lost at 100" 0.0065 gram.. ............................ = 2.38 per cent. Calculated for above formula ................ = 2.27 ,, 0.2665 gram of anhydrous base gave 0.6495 C02 and 0.1890 H20. Calculated. Found. Ca,. ................. 516 66.75 66.46 H51 ................51 6.60 7.8 7 N .................. 14 1.81 0 1 2 . . - ................ 192 24.84 - On stirring up this base with just enough dilute nitric acid to dis- solve it, adding a little concentrated acid, and rubbing well, a finely crystallised nitrate was formed : the gold-salt also crystallised from hot alcohol in well-defined anhydrous rosettes.172 WRIGHT AND LUFF ON THE 0.4700 gram gave 0.0840 Au ................ = 17-87' per cent. Calculated for C,6R4,(C,H,0)N0,,,HCl,AuC13 . . = 17.63 0,7190 gram of the base dried at 100" was saponified by alcoholic potash at 100" in 8 soda-water bottle; on evaporation, treatment of residue with hydrochloric acid and ether, and spontaneous evapora- tion, 0.2940 gram of mixed acids were obtained with a minute quantity of resinous bye-product ; on titration, this nentralised alkali eq_nivalent to 0-2890 gram of C9H,,0,+ C,H,O, ,, Found.Calcubted. By titration. By weighing. CJ3,OOh + C7H6OZ .. 39.33 40.19 40.89 Analogous experiments with pseudaconine show that it is capable of yielding benzoylated and acetylated products ; experiments on this subject are in progress, as al<so attempts to synthesise pseudaconitine from its saponification-products b r inversion of the action taking place during saponihation. $ 6. Constitutio.rt of Pseudacoizit Ine and its Derluccti7;e.s. From the circumstance that pseudaconitine splits up by a reaction of sajponification into peudaconine, C27H41N0E, and dimethylproto- catechuic acid, known to be indicated by C6H31 0.CH3 , it results that pseudaconitine may be written- CO.OH 1 0.CH3 The ready formation of apopseudaconitine by dehydration, and of acetyl and benzoyl apopseudaconitine by the action of glacial acetic acid and acetic and benzoic anhydrides, indicates moreover that pseud- aconitine is a trihydroxylated base ; so that the following formula? may be ascribed :- Psendaconitine ............( C,7H37N05)~OH '0": L O . C0.CsH3( 0.CH3)2 A popseudaconitine ( Cz7H,,NO6)-0H do Acetyl apopseudaconitine. ... ( C,,H,N05) do -O.C,H,O ........ 'O.CO.C,H,( O.CH,), \O .GO GH, ( 0. CH,),ALEALOIDS OF THE ACOXITES. 173 Benzoyl apopseudaconitine . . ( C2,H,NO,)-O. //O C,H,O ’“0: Apopseudaconine . . . . . , . . . . (CnH3,NO5)-0H Yo ‘0. C 0. C6H3( 0. C H,) Pseudaconine . . . . . . . . . . . . . ( C2,H37N05)10H \OH ‘OH The relationship between pseudaconitine and pseudaconine would therefore be expressible by applying to the former the unwieldy term “ dimethylprotocatechuyl - pseudaconine ” : whence acetyl-apo- pseudaconitine would become “ acetyl-dimethylprotocatechuyl-apo- pseudaconine,” and so on ! Experiments now in progress indicate that aconitine from A.nopel- Zu.s has an analogous constitution ; applying the term aconirm to the base, C2613:.9NOll, into which, together with benzoic acid, aconitine splits by saponification, the relationship of aconitine to this base is indicated by applying to the former the term “ benzoyl-aconine,” and the formula, ( C,H3,NOlo)-O-C7H50 ; which apparently may be further dissected, thus, (C2sH,N07)-OH -OH , aconitine being a- trihydroxylated base.Evidently the quadrivalent radicles, C27H3,N05, and C26H35N07, of pseudaconitine and aconitine respectively are closely allied : experi- ments with a view to elucidating the “ structure ” of these radicles are in progress, though as yet no results of importance have been arrived at. It is specially noteworthy that pseudaconitine is thus closely con- nected with the opium alkalo’ids narceine, narcotine, and oxynarcotine, all of which split up, giving rise to substances which are derivatives of dimethyl-protocatechuic acid (I3 eckett and Alder-Wright, this Journal, 1875, 573 ; 1876, i, 281 and 461). Moreover it is remarkable that all the natural alkalo’ids which have hitherto been split up by saponification-reactions yield acids of the aromatic series : thus with narcotine, nnrceine, oxynarcotine, pseudaconitine, aconitine, atropine (Kraut, Jahresbericht, 1865, 448), cocaine (Lossen, ibid., 4-51)> and piperine (von B abo and Keller).Experiments now in progress with the alkalo‘ids of Sabadilla seeds, however, show that the so-called “ veratria” of commerce is a mixture of afkaloYds, two of which belong t o the saponifiable class, one giving rise to the same dimethyl- protocatechuic acid as peudaconitine, the other forming an acid of a /OH ‘0 .C,fl50 0 2174 WRIGHT AKD LUFF ON THE, ETC. different kind, apparently identical, or isomeric, with CL ,zgcZic cccirb, C,H*O,. § 7. Otlzer Bases contained in Conwnercial (' Aeonithie " f i . 0 ~ ~ A. ferox. In the preparation of pure pseudaconitine nitrate as above described (§ 1) from the crude drug supplied by Messrs. Hopkin and Wil- liams, there was obtained a nitric acid mother-liquor from which no crystals could be obtained, but which contained a considerable amount of alkaloidal matter. On dilution with water, this deposited some resinoid matter; from the filtrate from this alkalies threw down a copious white amorphous precipitate. The precipitate thus obtained with sodium carbonate dissolved readily in ether, but furnished no crystalline base or salt by any kind of treatment tried. The base recovered from the ethereal solution as a varnish, and dried at 100", contained- Carbon ............... 63.37 Hydrogen ............ 8.01 Nitrogen.. ............ 3.21 and on saponification it formed dimethylprotocatechuic acid to the extent of 19.7 per cent. (calculated from weight of acid obtained from ether; 18.5 per cent. by titration), from which i t would appear it consisted largely of some substance closely allied to pseudaconitine, not improbably an alteration-product formed during extraction, and possibly identical with the amorphous base obtained by heating pseudaconitine acetate (9 1). The sodium carbonate filtrate from this precipitate was evaporated to dryness, and the residue treated with alcohol ; a quantity of brown amorphous alkalojidal matter was thus dissolved out : on evaporating to dryness and treating with water, a considerable portion dissolved, consisting apparently of impure pseu- dnconine, as i t formed only minute amounts of dinicthjl protocatechuic acid on saponification. From these results it is evident that the commercial alkaloid is liable t o be admixed with considerable quantities of amorphous bases : i t was estimated that about a fifth of the material obtained from Messrs. Hopkin and Williams consisted of such substances ; al- though the amorphous bases were not destitute of physiological potency, yet they appeared to produce far less lip-tingling, &c., than pure pseudaconitine. The nitrate of pseudaconitine being almost in- soluble in nitric acid containing 8 to 10 per cent. of HNO,, it would appear desirable that only the crystallised salt, or the alkaloid thence regenerated, should be prepared for medicinal use, which could readily be accomplished in practice.

ISSN:0368-1645    

DOI:10.1039/CT8783300151

出版商:RSC    

年代:1878

数据来源: RSC

摘要:

17’5 XX.-Ort a Xisnpli’jicatiort of Begnnult’s Nethod for Determiizing Boiliq Points with small quantities of Substance. By H. CHAPMAN JONES, F.C.S. THE want of a method of determining boiling points by which a per- fectly definite result can be obtained by the expenditure of only a moderate amount of time and trouble, and the employment of only a small quantity of the substance under investigation, has probably been felt by many. The disadvantages of the ordinary process are several, the chief being the varying coiiditions under which different experi- menters work, and the necessity of vaporising a considerable quantity of the substance. The boiling point of a body may be defined as the temperature at which the tension of its saturated vapour is equal to the standard atmospheric pressure.The first method that suggests itself for deter- mining this temperature would be to introduce a small quantity of the substance into a barometer tube, filled with mercury, and inverted in a reservoir of the same metal, and then to heat the experimental tube, noting the temperature at which the mercury is at the same level outside and inside the tube. But such an experiment may be greatly simplified. If a syphon barometer tube is used, the separate cistern is dispensed with, and as it is only needed to observe the temperature at which the mercury stands at the same level in both limbs, the tube may be very greatly reduced in length. Practically, a piece of ordi- nary quill tubing, about 4 mm. internal diameter, and 200 mm. ( 8 inches) long, bent upon itself, so that the open end extends at least 1.5 mm.beyond the other, which is closed, is all that is necessary (vide Fig. 2). For the sake of convenience such a tube will in future be called a tension-tube. The filling of these tubes with mercury, and the introduction into the closed end of a drop of the liquid to be examined, was the first difficulty of importance. I found that it was possible, by the exercise of a considerable amount of patience and perseverance, to charge a tension-tube, and keep it pivetty free from air, by filling it with me]*- cury, except a small space at the open end, then adding the substance. closing the tube, and inverting, &c., exactly after the manner of work- ing with a bent eudiometer. Such an operation, however, is far too uncertain and tedious to be practically useful.I therefore tried to introduce the substance at the end of the tension-tube at which it was to remain, by means of a capillary opening. As this method has some advantages which will occasionally, perhaps, render it preferable to the one subsequently described, I will give the details of the mani- pulation.176 JONES ON A SlillPLIFICATION OF REGNAULT’S The tube is made as before directed, but instead of closing one end, it is drawn out to a capillary tube, about 60 mm. long, and bent as shown, Fig. 1. Mercury is then poured into the tube, until it is nearly full, when it is examined to see if any air bubbles remain in the FIG. 1. + size. limb that is t o be closed. Such bubbles can easily be removed by tapping or gently warming the tube, or, if they adhere obstinately, by emptying and refilling.When the tube is free from bubbles, mercury is added, till it begins t o drop from the capillary tube, and stands up above the walls of the tube at the other end. The damp thumb is now pressed upon the wide end, and should drive out more mercury from both ends of the tube. The apparatus is next inverted, and the‘ capillary opening introduced below the surface of the liquid for exami- nation ; then the thumb should be relaxed a little, and mercury allowed to flow out till the substance is drawn into the capillary tube, and occupies 30 or 40 mm. of it. A little air is then drawn in, and the capillary tube sealed in a small flame. The mercury is now removed from the open end down to the bend, by means of a pipette, and the bubble of air in the capillary tube reduced in size, by gently warming to expand it, and then re-sealing as close as possible to the liquid.This operation may be repeated, but by no means have I been able to get quite rid of the air. This bubble, which should not be larger than a pin’s head, entirely prevents any disposition of the substance t o become overheated in the bath employed, because of its adhesion to the glass, but at the same time it lowers the apparent boiling point. This method has one other great disadvantage, namely, that it cannot be used with safety when dealing with substances that are changed on ignition. The approximate amount of error to be expected from these causes will be seen from the three following cases, whereMETHOD FOR DETER3lINIKG BOILING FOISTS, ETC.17 7 the upper figures show the true boiling point (determined by the method subsequently described), and the middle row of figures the results obtained by the method just detailed. In the 1st. CS?, the bubble was not reduced at all ; in the 2nd. it was reduced as far as possible by the method given above. The greater difference in the case of ethylic iodide may be attributed to the change brought about in a small quantity of its vapour by the operation of sealing off the capillary tube. cs2. csp C2H.51. OH,. 46.2 46.2 72.2 100.0 45.9 46.0 70.7 99.3 Difference -3 -2 1.5 -7 The only way in which I have succeeded in charging tension-tubes without chance of failure, and with perfect elimination of air, is by driving out the air by the vapour of the substance itself.This is effected by introducing about two drops of the liquid to be examined into the tube, running it round to the closed end, then introducing the open end into some mercury contained in a small porcelain crucible. This arrangement, supported by a suitable sling, made of copper wire, is lowered into a water or paraffin bath, according t o circumstances (see Fig. 2), and the temperature gradually raised. The air of the tension-tube is thus driven out in bubbles, which rise through the mercui-y and the liquid in the bath ; the air is, of course, followed by ------- ‘L I FIG. 2. f size.178 JONES ON A SIMPLIFICATION OF REQNAULT'S the vapour of the substance. These bubbles come off with increased rapidity as the temperature of the bath nears the boiling point of the :)ody used, and at about from 4" to 6" above it, there is a very marked increase, the action becoming violent if pushed much further.By observing the temperatures at which these changes take place, the boiling point of the substance may be ascertained to within 2" or 3', a precaution which should never be omitted, as it saves subsequent trouble. When enough vapour has escaped to sweep out all the air, the bath is allowed to cool, or, if the temperature is not above 50" or 60°, the tube with the crucible containing mercury may be at once removed from the bath. In either case as the vnpour in the tube condenses, the mercury rises, and completely fills it, except the space occupied by the drop of liquid at the top of the bend.The tension- tube is now released from the sling, and then removedfrom the crucible of mercury, and turned over by one operation, taking care that the closed limb shall be uppermost, so that the liquid may rise into the closed, and not into the open end. If the water (or paraffin) and mer- cury are nowremoved from the open limb by means of filter paper (or cold wire) and a pipette, the tube is ready €or use. This method of filling a tension-tube, or rather of making it fill itself, is exceedingly simple in manipulation, and perfectly satisfactory. A tube so filled, after nine days had elapsed, during which it had been used two or three times, did not show the slightest evidence of ariy air having gained access to the closed limb, and could be heated a degree or two above the boiling point of the liquid without vaporisation taking place.We now pass to the method of using these tubes. The temperature at which the mercury is at the same level in both limbs, will be the boiling point of the substance. To ascertain that temperature, the tube must be introduced into a bath of transparent liquid contained in a glass vessel, so that the closed end is below the surface, and the open end is freely exposed to the air. The bulb of the chief thermometer should be brought as close as possible t o that portion of the closed limb which will be occupied by the vapour of the body, and a second thermometer arranged as described below. The temperature is then gradually raised, and the tube carefully watched as it approaches the boiling point of the substance. I f the level of the mercury does not sink as soon as you judge that it should, the open end of the tube, which projects from the bath, should be gently tapped vertically by a hard substance (glass or metal).This gentle jerk will entirely obviate the difficulty. But if by accident or neglect the temperature of the bath has risen 2" or 3" above the boiling point of the substance, and consequently the mercury sinks with increasing instead of with di- minishing rapidity, we can prevent, the contents of the tube from being driven out, and the experiment lost, by raising the closed end a littleMETHOD FOR DETERMINING BOILING POlSTS, ETC. 1'79 out of the bath, and lowering it into the bath again only as the tempera- ture falls.(It will be observed t'hat if the tube is filled by the second method and is free from air, the approximate boiling point is ascer- tained during the filling.) With common care, however, such an acci- dent will never occur, but the mercury in the closed limb will gradually sink, until it is lower than the mercury in the open limb ; on cooling, the mercury will rise again, and so by alternately heating the bathand allowing it to cool, the two mercury levels can be made to pass one another any number of times. Each time that the lercls correspond, the temperature is noted. Six is a very convenient number of such observations to make, three as the bath is rising in temperature, and three as it is cooling. It is perfectly easy to keep these oscillations within half a degree on each side of the boiling point, and If" on each side of it should be the maximum.The average of six such observations may be taken as the uncorrected boiling point, unless the first temperature evidently disagrees with the rest, when the first two observations are neglected, and two others substituted for them. This error will occur when the temperature of the bath has been raised too quickly, so that the tension-tube, with its contained mercury, has not been able to keep pace with it. The tube, when done with, may be labelled and preserved, if worth while, so that the observations can be confirmed a t any future time. The boiling point so determined can be regarded only as approxi- mate unti1 it is corrected, and as all the boiling points given in this paper have been reduced to standard conditions, to make them com- parable, it may be well to state here the exact corrections that have been applied.It is necessary to observe the height of the barometer, and the temperature of the air, and thus to get the height of the barometer a t 0" C.; also to observe the mean temperature of that portion of the thread of mercury in the thermometer that is not im- mersed in the bath. To ascertain this temperature a second thermo- meter is used, the bulb of which is placed half way between the level of the liquid in the bath and the top of the mercury in the chief ther- mometer. Every time the temperature is to be taken, both thermo- meters must be read ; then the number of degrees of the mercury of the chief thermometer that are not in the bath is to be multiplied by the difference in temperature between the two instruments, and the product multiplied by *0001545 (the average coefficient of the appa- rent expansion of mercury in glass) ; the result is to be added to the temperature indicated by the chief thermometer, to obtain the real temperature.I f the work is carried out as above described, there will be six such actual temperatures obtained, the average of which gives the boiling point under the pressure observed. The correction for pressure is made by multiplying the number of180 JONES ON A SIMPLIFICATION OF REGNAULT'S mm. by which it differs from 760, by -037 (that is, the fraction of a degree by which the boiling point of water varies for each mm.of barometric pressure, starting at 760 mm.), and adding the result to or subtracting it from the temperature observed, according to whether the pressure is below or above the normal pressure. A temperature so obtained is designated simply the boiling point. I have made a good many experiments to ascert'ain the degree of accuracy that may be expected by the use of this method, and to show the effects of varying circumstances upon it. In these experiments I have carefully avoided any refinement of apparatus, or the spending of an undue amount of time over each operation, so that the results truly show the applicability of the process to the ordinary require- ments of a laboratory, where the observation d boiling points ia but of rare occurrence. The apparatus used was the following :- A thermometer by N e g r e t t i and Zambra, graduated from -5" to 105" C., each degree being divided into 5 parts.This was compared with a Kew standard at the ordinary temperature and found correct, and it registered 99*8-99%-99.9, instead of 100, for the boiling point of water. -2" is therefore added to its indications at about 100, and a corresponding correction is made for other temperatures. Its read- ings are given to *lo, but the last figure must not be taken as absolute ; the error may, however, be considered as less than -1". An ordinary thermometer divided into single degrees graduated up to 360°, which was found fairly correct. A beaker of a little more than half a litre capacity, as a water-bath, and one about half its capacity for the paraffin-bath. It would have been better if the size of the paraffin-bath had been increased. These were placed on a thick iron plate, or a piece of tinned iron (tinplate2 supported on a tripod, and warmed by means of a Bunsen burner.The two slings used for supporting the apparatus were made out of copper wire, the fingers being the only tools. Bisulphide of carbon was the first substance employed. It is stated to boil a t " 46.6" under ordinary pressure." A small quantiiy of it was digested with sodium and then distilled without visible ebul- lition, by placing the retort containing it in warm water. The great variations of the barometer in November last, enabled me to make observations a t very different pressures. The following are the tem- peratures observed for the difei-ent pressures, the lowest line being the boiling point deduced from each experiment :- Pressure in mm... . . . . 736.0 744.5 752.0 762.0 B.P. at above pressure. 45.1 45.5 46.0 46.3 B.P. a t i60 mm. . . . . 46.0 46.1 46.3 46.2METHOD FOR DETERMINIXG BOILIXO POIXTS, ETC. 181 Each of these temperatures is the average of from 5 to 10 observa- tions, made as before described, the greatest difference between any two observations in anyone series being -2". The observations in any one series are often all exactly alike, and could almost invariably be made so by working a little more slowly. The following is a speci- men of what may be expected, the second decimal place being caused by the correction for exposed t,hread of mercury in the thermometer.The lst, 3rd, 5th, &c., were taken as the temperature of the bath was rising ; the 2nd, 4th, 6th, &c., as it was falling :- 46*04A5*90A6*0446~0O-45~99-45~95-4.Eib99-45*99- 45-99-4599. A sample of e t h y l i c iodide, which I believe is pure, was tested by this method, and its boiling point found to be 72.2". A determination by Dr. F r a n k l a n d (when corrected for pressure) gave 72*1", when tlie thermometer bulb was in the vapour, and 72.7 when immersed in the liquid. The entire time occupied by the above determination (including the making of the tension-tube) was 19 hour, much of which time was occupied in heating the water-bath, no attention being then necessary. Two determi- nations of its boiling point made by fixing the thermometer with its bulb a little above the surface of some water kept rapidly boiling in a flask, gave 100.1" and 100*0".These experiments were made quite independently at an interval of ten days. The boiIing point of water, taken by means of a tension-tube and a paraffin-bath, was found to be 100.0". Some phenol was prepared from solid carbolic acid by distilling and collecting when the distillate was homogeneous. The portion collected came over between 1 8 3 O and 185". The phenol was liquefied by immersing the bottle containing it in warm water; the tension- tube was slightly warmed, and a drop or two introduced by meam of a small pipette. The boiling point was found to be 183F, but a t this high temperature the tension of mercury-vapour becomes appreciable (= 11 mp.) ; so, deducting this from the barometric pressure, and recalculating, we get 184' as the boiling point.This agrees with a determination by Scrugham, who found the boiling point to be 184", whereas L a u r e n t made it 187" to 188". The next substance employed was benzoic acid. This body is slated to melt at 121.4" and boil at 250". The tension-tube was charged as usual, the acid vaporising abundantly a t 256". The snb- stance solidified on cooling a t the bend of the tube, but was driven to the top of the closed limb without the least difficulty by gently warm- ing it in a small flame. As the paraffin became practically opaque by W a t e r was the next substance experimented with. VOL. XYXIII, P182 JONES ON A SIXPLIFICATION O F REGXNAULT'S METHOD, ETC.heating it to this high temperature, the experiment could not be finished ; but if a suitable substance were found to replace it, the only difficulty of these experiments at such temperatures would be sur- mounted. Inasmuch as substances operated on are not alwajs pure, it is well to know the effect that solids in solution, liquid impurities, &c., have upon the boiling point of a body. The following experiments were undertaken with this elid in view. A strong but not saturated solution of calcic chloride gave a boiling point of 1 1 9 + O . A saturated solution of common s a l t was then experimented with as follows. An ounce or two was introduced into a capacious flask, some scraps of platinum dropped in, and the solution heated till it boiled briskly. A thermometer with its bulb immersed in the liquid was stationary at 108$", and when raised so that the bulb was about 1* inch from the surface of the liquid, it fell only or 6 a degree.The boiling point taken by means of a tension-tube was found to be 107r. A minute bubble of air was afterwards discovered in the tube, which accounts €or the discrepancy observed. The separation of solid salt tended to prevent a very satisfactory operation. These experiments show that solid substances in solution tend to raise the boiling point of the liquid, that is, the tension of the vapour of the solvent is lowered. A mixture of alcohol and water gave ft boiling point of 82.0°, showing that a mixture of liquids that mix with one another, or that are mutually soluble in each other, gives a boiling point intermediate between the boiling points of its constituents. Some carbonic disulphide and water mere introduced into a t,ension-tube, and the apparent boiling point determined.It was found to be 43.$", showing that a mixture of liquids which are not soluble in each other, gives an apparent boiling point lower than that of either separately, that is, the tensions of their vapours are added. By deducting from the pressure observed, the equivalent for the tension of water vapour at, the observed temperature, and recalculating for the reduced pressure, we obtain from this experiment 45.7" for the boiling point of CS2, its actual boiling point being 46.2". It, was not considered necessary to multiply these experiments, as they agree perfectly with well known laws.In conclusion, I think that the advantages of this method will be found to be:- 1st. The obtaining of definite, constant, and perfectly comparable results. 2nd. Diminution of error of observation, as several readings can be taken. Paraffin is suitable for use up to about 200".JOEINSON ON CERTAIN POLSIODIDES. 183 3rd. The fact that a singIe drop of any substance is all that is 4th. That the method can at any time be rendered more exact, by needed. litble refinements that will be obvious to any experimenter. Postscr@f.-On communicating the results of the work detailed above to Dr. Frankland, he was good enough to tell me that sper- maceti could be used at higher temperatures than paraflin. I find that spermaceti will bear heating up to nearly 300" C. without losing its transparency or evolving an inconvenient amoiint of vapour ; the only drawback to its use for all temperatures over 80' or 90" is that it would probably be more readily acted upon by the vapour of substances passing through it than paraffin. Dr. Frankland was also so kind as to give me small quantities of the following substances to examine by my method. No. 1 was a sample of methylic iodide, and No. 2 a sample of ethylic diethoxalat,e, ( {(cc2H5)2'0H)7 o. o(c2H,) B.P. stated as 175" C. (barometric pressure not known). 'Both these were the ordinary preparations of the'laboratory. No 3 was a, sample of commercial benzol, known to be impure. The boiling points I found were as follows :- 1. 2. 3. 42.8 1752 86.9 These results fully confirm the usefulness and trustworthiness of the method.

ISSN:0368-1645    

DOI:10.1039/CT8783300175

出版商:RSC    

年代:1878

数据来源: RSC