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.

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    Experimemt V. Performed in the same manner 1. 2 cems. albumen solution = *23 gramme + 13 CCS. 18 per cent. HCl. 2. 2 „ >) ~ '23 ,, + 7 » 342 „ HCl. 3. 2 „ ” ” ~ ” + 50 „ 045 ,, HCl. 4. 5 ,, )} )) =0/5 ,, + 9 „ 342 „ HCl. The results were :— 1. 10 T 7 per cent, of acid, free HCl present. 2. 10-4 3. 9’18 ,, free HCl absent. Acidity of Nos. 3 and 4 were *044 per cent, and *219 per cent, respectively. It is more difficult to arrive at the exact amounts of each when both free and combined hydrochloric acid are present in the same solution. Drying a few cubic centimetres at 100° Cent, drives off the free HCl; but the charring of the proteid, and the resolution of some of it into simpler forms, one of which has a violet colour (Liebermann’s reaction for free HCl), tend to vitiate the results. Adding, drop by drop, a decinormal solution of sodium hydrate until the fluid tested ceases to give any reaction with vanillin-phloroglucin is also fallacious, as some of the combi-ned acidity is affected as well as, and at the same time as, the free. Neutralisation of the free HCl with carbonate of barium, which is said not to affect the combined acid, gives better results, but the process is tedious. On the whole, I prefer drying the fluid at 100° and then titrating again: the difference between the total acidity and the acidity left after drying gives the free HCl, and the fallacy present is constant and very small, the free acidity in fact being always slightly too great, the combined slightly too small. Although this combined acid is equal quantitatively to the original free HCl, it has not retained any of the other properties of the free acid in the same projDortions. For, as I have said above, it does not give any of the common reactions for the free acids, but on investigating its action further I find that its antiseptic property is very slight. I have grown the Staphy- lococcus pyogenes aureus in a ’68 per cent, solution of combined HCl,^ while the amylolytic action of saliva goes on in a solution of combined acidity double the strength of that necessary, if the acids were free, to destroy the ferment. ^ Journal of Pathology, 1892.
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