A microscopical method of determining molecular weights / by George Barger.

  • Barger, George, 1878-1939.
Date:
[1904?]
Catalogue details

Licence: Public Domain Mark

Credit: A microscopical method of determining molecular weights / by George Barger. Source: Wellcome Collection.

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    II. Cinnamic acid ; 29’6 grams per litre ; methyl alcohol and chloroform not specially purified. 80 per cent. rbcnzil0T9 mole. 50 mins. + 4 -7 + 1 -11 + 5l i mean = 0*195 chloroform \ n 0-20 1 1 12 „ -7 + 1 -3 +1 -2, f M. AV. =152 90 per cent. r 1 1 0T75 11 40 >j + 2 -4 0 + 1 + 31 L mean = 0 18 chloroform \ 1 ) 0-185 11 55 ,, +5 + 1 -3 + 12 - 3 J 1 M. W. =164 94 per cent. r 11 0-15 11 8 „ +2 -2 + 2 -3 + 4 \ mean = 0*155 chloroform i 1 1 0-16 1 1 90 „ -5 + 13 0 + 20 + 3j f M. W. = 191 100 per cent, f 1 1 0-119 1 1 1 hour +7 + 1 + 5 -4 + 6 ^ mean = 0-122 chloroform i 11 0T25 11 15 mins. -10 + 6 -13 + 9 - 25 J h M. W. = 243 The molecular weight of cinnamic acid in 100 per cent, methyl alcohol has not been determined, but in ethyl alcohol it was found to be 148. The values for benzoic acid may be slightly vitiated by its relatively considerable vapour pressure at the ordinary temperature. With the molecular weights as ordinates and the percentage of benzene or chloro¬ form as abscissse, two curves have been plotted which clearly show that a small proportion of alcohol is sufficient to do away with the associa¬ tion. Should this observation prove to be general, it may be of con siderable practical importance in those cases where one is restricted to associative solvents because the substance is not sufficiently soluble in the others. A [small percentage of a non-associative solvent would not materially affect the solubility, yet it would reduce the molecular weight to its normal value. The Wellcome Physiological Research Laboratories, Herne Hill, S.E % R. CLAY AND SONS LTD.. BREAD ST. HILL, E.C , AND BUNGAY, SUFFOLK.