Open AccessThe combination curves, hydrogen ion regulating power and dissociation constants of gelatin
Author(s) -
E. B. R. Prideaux
Publication year - 1931
Publication title -
proceedings of the royal society of london. series b, containing papers of a biological character
Language(s) - English
Resource type - Journals
eISSN - 2053-9185
pISSN - 0950-1193
DOI - 10.1098/rspb.1931.0034
Subject(s) - gelatin , titration , chemistry , alkali metal , titration curve , dissociation (chemistry) , ion , dissociation constant , acid–base reaction , base (topology) , molecule , acid dissociation constant , inorganic chemistry , thermodynamics , aqueous solution , organic chemistry , mathematics , biochemistry , mathematical analysis , physics , receptor
The existing titrations of gelatin with acid and alkali have been found to refer mainly to solutions containing approximately 1 per cent. of the dry material, while the few titrations in 0·1 per cent. solutions are not in agreement. A series of titrations with alkali at both concentrations of gelatin has been made with a view to deciding whether the combining weight is really affected by the concentration. From the collected data, the combining or equivalent weight has been calculated by a new method based on the theory of buffer mixtures, and incidentally, the buffer capacities at the different concentrations have been determined. The equivalent so found has been compared with those which have been deduced by other methods. The equivalents of the 1·0 per cent. and 0·1 per cent. solutions in the alkaline range have also been calculated by another method using constants, and found to differ from one another. The equivalents as acid and as base have been deduced in various ways from the combination curves and also from the cleavage products, and these acid/base ratios have been compared. Finally by treating gelatin as a simple ampholyte, apparent constants have been calculated both on the undissociated molecule or older and on the "amphoteric ion" or newer theory. Although gelatin is undoubtedly amphoteric in its nature, yet its curves of combination (p H plotted againstx = added acid or alkali) differ greatly from those of simple amino-acids such as glycine, as is easily seen by comparing the types which have been portrayed by Harris (1923, 1925, 1930).