On the gastric digestion of proteids / by A. Lockhart Gillespie.

Date:
[1892?]
Catalogue details

Licence: Public Domain Mark

Credit: On the gastric digestion of proteids / by A. Lockhart Gillespie. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    18/30 (page 212)
    addition of ammonia, for instance, causing the precipitate to contain 10‘7 per cent, of silver. Loew estimated the amount of the silver by dissolving the ash of the washed precipitate in nitric acid, precipitating with hydrochloric acid, and weighing as chloride of silver. He considered that atoms of metallic silver were attached directly to the proteid molecule. Fuchs (Ann. Chem. Pharm.^ Bd. 151, p. 372) found in his silver albuminate an average of 3’28 per cent., but he always had an excess of albumen present. Loew also investigated the amount of silver which combined with “peptone,” but in those days “peptone” comprised albumoses as well as true peptone. He only made three analyses with a mean of 11 per cent, of silver. All through his work this observer has theorised from too scanty grounds, two or at most three analyses sufficing in each case. As the percentage of silver to albumen varied so much in these results, it was doubtful whether the bodies obtained were true chemical combinations or not. But it seems likely that a molecule of silver may take the place of one molecule of water, or that two or more may be so added to the albumen. Loew’s figures are also borne out by Harnack’s copper compounds. This observer succeeded in separating two series of cupric-albuminates, which correspond closely to the first two silver compounds of Loew. I have made an extended series of observations on the silver salts of the proteids. For this purpose I separated the globulin from white of egg as described above (p. 196), neglecting however the salts. These, however, I estimated in the usual way, calculating also the weight of chlorine by precipitation of the dissolved ash with nitrate of silver. I adopted the same procedure with regard to the other members of the proteid group. In the case of deutero- albumose and peptone, I found that so much of the proteid was lost during the dialyses necessary to abstracting the salts, that it was better to calculate the ash and chlorine as above stated. All the specimens of individual proteids, however, were free from traces even of the others. I added to each proteid in turn an excess of silver nitrate, dissolved in distilled water, the solutions being of unknown strength, but usually above 10 per cent. The precipitate with albumen was pure white, flocculent and comparatively light, the solution filtering slowly. With proto-albumose the precipitate was finer, of a bright light-yellow colour and filtered well. Deutero-albumose, on the other hand, gave an orange yellow, fine, heavy precipitate, filtering rapidly, while peptone afforded a slightly yellow, very minute pre- cipitate, which filtered badly, much going through the filter-paper at first, and which washed extremely ill. The precipitates were washed with distilled water until no further reaction was given