摘要:

ABSTRACTS OF THE PROCEEDINGS OF THE CHEMICAL SOCIETY. No. 53. Session 1888-89. May 3rd, 1888. Mr. W. Crookes, F.R.S., President, in the Chair. Certificates were read in favour of Messrs. Joseph Campbell, Glen Innes, New South Wales ; John Dunn, Myrtle Cottage, Downfield, Dundee ; William Burns Featherstone, Showelhurst, Moseley, Bir-mingham; Albert L. Guiterman, Ph.D., 36, Primrose Hill Road; James C. Hamilton, King’s Cavil, Linlithgow, N.B. ; James Mair, B.Sc., 181, Hospital Street, Glasgow, S.S. ; Edward William Alfred Augustine Mayhew, Freemantle, Western Australia ; John James Morgan, Highfield House, Ebbw Vale, Monmouth ; Frederick Ernest Pollard, Administration des Services Sanitaires et d’Hygihe Pub- lique, Cairo, Egypt; Albert John Sach, Goulburn, New South Wales, Australia ; Mark S.Wade, M.B., Clinton, British Columbia. The following papers were read :-36. “ The Determination of the Molecular Weights of the Carbo- hydrates.” By Horace T. Brown and G. Harris Morris, Ph.D. The molecular weights of the carbohydrates have, with one or two exceptions, never been determined with any certainty. The excep- tions-dextrose and levulose-have been shown indirectly by Kiliani to have a molecular weight corresponding to the formula C,H,,O,, The generally accepted views witth regard to the other carbohydrates are based entirely upon certain indefinite derivatives, and only give the mi?zirnurnsize of the molecules. Quite recently V. Meyer (Bey., 1888, 556) and Auwers (ibid.,1888, 860) have drawn attention to the method devised by Raoult for the determination of molecular weights.The method is applicable to all organic substances, and is of especial value in ases where a vapour-density determination is not possible. Biagden, in 1788, established the fact with regard to inorganic salts that the lowering of the freezing point of their aqueous solutions is proportional to the weight of substance dissolved in it constant weight 5s of water. De Coppet in 1871-72 extended these results and pointed out that when the lowering of the freezing point is calculated for a given weight of the substance in 100 grams of water, the result, which he terms the coeflcient of depression, is constant for the same substance, and that the coefficients for different substances bear a simple relation to their molecular weights. Raoult extended the law to organic substances and to other solvents besides water.He showed that when certain quantities of the same substance are successively dissolved in a solvent upon which it has no chemical action, there is a progressive lowering of the point of con-gelation of the solution, and this lowering is proportional to the weight of the swbstance dissolved in a constant weight of water. If C be the observed depression of the point of congelation produced by z grams of the substance dissolved in y grams of the solvent, then the de- pression A produced by 1gram of the substance in 100 grams of the solvent is given by the formula = A.If the value A, which x x 100 Raoult designates the “coefficient of depression,” of the respective substance for the respective solvent is multiplied by the molecular weight M of the dissolved substance, we get M x A = T, the so-called “molecular depression ” of the substance in question. T is a value varying with the nature of the solvent, but remaining constant with the same solvent for numerous groups of compounds. Raoult finds that for water T = 19 for all organic substances with one or two exceptions. From this it follows that having determined experi- mentally the value of A for any substance, and knowing the value of T, the molecular weight M for the substance in question may be Tobtained by dividing A into T : for M = -.A The method employed by the authors is essentially that of Auwei-s (Ber., 1888, 712), the solvent employed being necessarily water.The thermometer used is graduated into twentieths of a degree centi- grade, and with the aid of a telescope can be easily read to one two- hundredth of a degree. The following results were obtained:- Dextrose.-Calculated for C6H,,0,. Found (mean). A = 0.106 A = 0.1052 M = 180.0 M = 180.2 Cane-su gar .-Calcula ted for CI2H,O l. Found (mean). A = 0.0555 A = 0.0562 M = 342.0 M = 337-5 Maltose.-Calculated for C12H2,0, I. Found (mean). A = 0.0555 A = 0.059 M = 342.0 M = 322.0 Milk-sugar.-Calculated for C,,H&,,. Found (mean). A = 0.0555 A = 0.055 M = 342.0 M = 345.0 A solution of cane-sugar inverted with invertase gave before inver- sion M = 328, after inversion M = 174.3: clearly showing that 1mol.of cane-sugar splits up on inversion into two equal molecules. It was found that dextrose which exhibits birotation in solution has the same molecular weight as dextrose having the normal rotation. Mannit,ol.-Calculated for C6H1406. Found (mean). A. = 0,104 A= 0.105 M = 182.0 M = 181.0 Arabinose.-Calculated for C5HI0O5. Found (mean). A = 0.126 A = 0.1263 M = 150.0 At = 150.3 Raffinose.-Calculated for C,,H320,,-5H20. Found (mean). A = 0.032 A = 0.036 M = 594.0 M = 528.0 All the results are the mean of numeroufi extremely concordant experiments made with solutions of varying concentration. All tb e sacc harose s-cane -sugar, ma1 tose and milk- sugar-were found to have the same molecular weight, thus disproving the sugges- tions of Herzfeld and others as to their varying values.The authors have applied the method to starch and the non-crystal- lisable products of its transformation, but owing to unexpected difficulties, resulting from the smallness of the value of A for these substances, they are unable as yet to assign accurate values to them, although there can be no doubt that their molecular weights are extremely high. 37. “The Molecular Weights of Nitric Peroxide and Nitrous Anhydride.” By W. Ramsay, Ph.D. The author has applied Raoult’s method of determining molecular weights to nitric peroxide, and has ascertained the depression produced in the freezing point of pure glacial acetic acid by quantities of peroxide varying from 0.92 gram to nearly 9 grams of peroxide to 100 grams of acetic acid.It is found thatin every case the molecular weight of the peroxide is nearly 92, corresponding to the formula N,O,; the highest result was 98.58 and the lowest 90.29. These experiments establish the molecular weight of liquid nitrogen peroxide, even in dilute solution, and also show that no further molecular aggregation occurs even when the number of molecules of peroxide in a given volume is considerably increased. Similar experiments were made with nitrous anhydride, but the temperature of experiment (about 16”) is so high that dissociation occurred during manipulation. No definite results were’obtained.DISCUSSION. Professor DEBUSsaid he presumed that on dissolving urea in acetic acid combination would occur. Wonld the mulecular weight fou,nd be the same if a neutral solvent were used ? Also, did not acetic acid act on nitrogen tetroxide? Most liquids exerted a decomposing action on this substance. He was under tlhe impression that Raonlt’s method involved the use of a solvent which had no chemical action on the substance. Mr. WYNNEremarked that the molecular weight of acetic acid determined by Raoult’s method accorded with the formula C2H402. Now it was known that the vapour-density of acetic acid at a few degrees above its boiling point pointed to the formula C4H804,and that it was only at higher temperatures that the less complex molecule CzH4O2was obtained.It must, therefore, be assumed that the action of the solvent resulted in the complete dissociation of the complex molecules present in liquid acetic acid. Most results liitherto obtained by the use of Raonlt’s method pointed to a similar complete dissociation and would seem to show that the dissociation is not dependent on the particular solvent employed but took place in all cases ; the method, therefore, had so far failed to afford any indication of the molecular complexity of liquids and solids. Referring to the formula C,2H220,,deduced by Messrs. Brown and Morris by Raoult’s method, Mr. Wynne asked what interpretation was to be placed on the results recently obtained by Winter in his investigation of the specific rotatory power of levulose and of invert sugar, which pointed to the presence in the latter of 3 mols.levulose and 4mols. dextrose. If these results were nccepied it would seem reasonable to suppose that the complexity of ths molecule of cane-sugar was greater than that indicated by the formula quoted. Dr. PERKINsaid that he had obtained results confirmatory of those brought forward. Using acetic acid as solvent, the molecular weight of naphthalene was found to be 134, and the values he had obtained for the isomeric citraconic, itaconic, and mesaconic acids were respec-tively 130.6, 130.9 and 138, the calculated value for the simple formula C6Hs04being 130. Mr. CRONPTONobserved that great irregularities were manifest on comparing the molecular depressions of various substances as deter- mined by Raoult : therefore, until more was known of the cause of such irregularities and of the mechanism of the changes under 61 discussion, such results as those brought forward by Messrs.Brown and Morris must, he thought, be accepted with great reservation. Dr. ARMSTRONGsaid that the results obtained by Raoult’s method were certainly very striking, but bearing in mind the complexity of the phenomena of dissolution, as there was undoubtedly much evidence to favour the conclusion that the molecules of many sub-stances in the solid and even in the liquid state were congeries of the fundamentaZ molecules, he was not prepared to accept the con- clusions arrived at as in any way final.If Winter’s results were accepted, it would be difficult to reconcile them with the conclusion that cane-sugar was represented by the simple formula C12H220n, Apart from the information as to the comparative moIecular weights of dissolved substances which Raoult’s method promised to afford, it appeared that in order to gain as complete insight as possible into the molecular composition of solids and liquids it was important to vary in every way the proportions of substance dissolved as well as the solvent : he therefore regarded V. Meyer and Auwers’ recent recom- mendation of acetic acid as the solvent as most unfortunate. Mr. HERONdoubted the correctness of Herzfeld and Winter’s determinations of the rotatory power of levulose. Mr.BROWNagreed with Mr. Heron that Winter’s statement regarding levulose required confirmation. The values obtained by Raoult were remarkably uniform for members of a group of com-pounds, and he was of opinion that the general consistency of the results obtained in the case of organic compounds was such as entirely to justify the claim that the results put forward by Mr. Morris and himself were to be accepted as expressing the facts. Professor RAMSAYasked : Was urea ac,state known ? [Beilstein does not mention it, although he describes the trichloracetate. Gmelin says that the lactate cannot exist, and states that urea does not combine with weak acids. Moreover, its formation would not mate- rially affect the result, as it would only be equivalent to the with- drawal of a small portion of the acid.] N,O, was without action on acetic acid; it, however, served as a most delicate test of water, a green colour being produced if water were present in the acid.He agreed that as great a variety of solvents as possible should be used. 38. “The Action of Heat on the Salts of Tetramethyl-ammonium.’’ By A. Th. Lawson, Ph.D., and Norman Collie, Ph.D. The research was undertaken to ascertain how the tetramethyl- ammonium salts would behave when heated and in what respects they would resemble the phosphonium and snlphine compounds. Most of the salts experimented with were found to be very deliqnes- cent and far more soluble than the corresponding ammonium salts, ti2 and when compared with the ammonium salts the order of solubility seemed in some cases to be reversed : in the case of the halogen salts the iodide is least soluble, the chloride and fluoride the most soluble.The oxalate and sulphate are extremely deliquescent, while the nitrate is one of the least soluble of the tetramethylammonium compounds and scarcely deliquescent. Nearly all the salts experimented on split up in a simple manner, trimethylamine and a salt of methyl being produced. The fluoride is an instance : (CHsj4NF= (CH3),N+ CH,F. But in some cases where the decomposition takes place at a high temperature and the methyl salt which is formed is not very stable, further decomposition occurs ; of this kind of decomposition the nitrite is an example :--4r(CH,),N*N02 = 4(CH,),N + 2(CH,),O+ 4N0 + 0,.39. “The Action of Heat on the Salts of Tetramethylphosphonium.” By Norman Collie, Ph.D., F.R.S.E. The action of heat on the salts of tetramethylphosphoniurn was studied, partly to complete a series of experiments which had been made on the mode of decomposition of the phosphonium salts when heated and partly to compare their decomposition ,with that of the tetramethylammonium salts when similarly treated. The salts of tetramethylphosphonium. with the oxy-acids, when subjected to the action of heat, undergo, as a rule, two different changes: the first and by far the most important is the produc- tion of trimethylphosphine oxide and a ketone-in the case of the benzoate : (C&)4PCO2C6H, = (CH,)sPO 4-CH,.CO*C6HS. The second change, and one which only occurs to a very limited extent, is when trimethylphosphine and a salt of methyl are produced: (CH3)aPCO2C6H, = (CH,),P + CsH,*CO2CJ&j. As regards the action of heat on the hydracid salts, the chloride is the only one which decomposes in a simple manner : 2(CE,),PCl = 2(CH,),PHC1 + CJL At the next meeting, on Thursday May the 17th, there will be a ballot for the election of Fellows, and the following paper will be read :-‘‘Researches on the Constitution of Azo-and Diazo-derivatives. IV. Diazo-amido By Professor Meldola, F.R.S., and F. W. Streatfeild, P.I.C. HARRISON. AND som, PSINTERS IN OXDINARY TO HER MAJESTY, ST. MARTIN’S LANE.

ISSN:0369-8718    

DOI:10.1039/PL8880400057

出版商:RSC    

年代:1888

数据来源: RSC