Practical organic and bio-chemistry / by R.H.A. Plimmer.

  • Robert Plimmer
Date:
1915
Catalogue details

Licence: Public Domain Mark

Credit: Practical organic and bio-chemistry / by R.H.A. Plimmer. Source: Wellcome Collection.

    589/660 page 569
    B-Hydroxybutyric Acid. It is difficult to prove the presence of @-hydroxybutyric acid in urine. Ifa large amount be present, the urine will show levo-rotation after fermenta- tion of the glucose. Its presence can only be shown with certainty by extrac- tion in the same way as it is estimated (p. 595). (2) PROTEIN. A. Coagulable Protein. (‘‘ Albumin.”) Most commonly coagulable protein is found and tested for by :— (1) Heat Coagulation. — This is best performed by heating after adding to a little of the filtered urine one-sixth of its volume of saturated sodium chloride. The precipitate which is formed may consist of coagulated protein or earthy phosphates, or both. The precipitate of earthy phosphates dissolves, whilst the coagulated protein separates out in flakes if 2 drops of 33 per cent. acetic acid be added for every ro ¢.c. urine. (2p freliex s Lest. Some urine is poured on to the surface of a little concentrated nitric acid in a test tube, taking care that the two solutions do not mix. To prevent this the nitric acid may be saturated with ammonium nitrate. If protein be present, a whitish ring will form at the junction. There may be also a . reddish ring due to indigo red and indigo blue. If the urine be concentrated urea nitrate may separate out, but here the precipitate is obviously crystalline. Uric acid may also separate if a large quantity of urates be present. This can be prevented by diluting before testing with the nitric acid. (3) Aydroferrocyanic Acid. This test is given under reactions of proteins (p. 367). (4) Zhe Colour Reactions cannot be applied directly to urine, but to the heat coagulum suspended in water. Millon’s reagent and the biuret reaction should be tried; the coagulum in the latter case is dissolved in hot caustic soda. 7 Characterisation and Separation of a Mixture of Proteins. (a) Albumin and Globulin.—The globulin is isolated by half-saturating the urine with ammonium sulphate, and filtered off. It is dissolved in 2 per cent. sodium chloride solution. The solution is acidified and heated. The albumin in the filtrate 1s’ coagulated on acidifying with acetic acid and heating. ‘The protein nature of the precipitates should be confirmed by the colour tests. ‘ (6) Proteose and Coagulable Protein.—The solution is saturated with ammonium sulphate (8 parts to ro parts urine) and heated for a few seconds, so that the coagulable protein is coagulated. The precipitate is filtered off and extracted with alcohol to remove urobilin, which also gives the biuret re- action. It is extracted with boiling water which dissolves the proteose. This solution is tested with the biuret, xanthoproteic and Millon’s reactions. (5) Lsttmation. The protein is estimated by Esbach’s method (see under proteins, p. 367). The urine must be acidified with acetic acid if it is not acid and diluted till its specific gravity 1s 1°006-1°008.
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