Physiology and pathology of the urine : with methods for its examination / by J. Dixon Mann.

  • John Dixon Mann
Date:
1904
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Licence: In copyright

Credit: Physiology and pathology of the urine : with methods for its examination / by J. Dixon Mann. Source: Wellcome Collection.

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    forms double salts with metals, some of which are but slightly soluble in water, a fact that is taken advantage of in order to precipitate creatinin from aqueous solution. When boiled with Fehling’s solu- tion creatinin reduces the copper salt, but at the same time prevents the precipitation of the oxide ; the reduction being simply indicated by the solution changing from blue to yellow. [See the action of glucose on Fehling’s solution.] Reactions.—WeyVs test.^—The presence of creatinin in urine may be detected by the addition of a few drops of a freshly-prepared, very weak solution of sodium nitroprusside and a few drops of a solution of caustic soda; a red colour is produced which quickly fades away. On the subsequent addition of excess of acetic acid, with the application of heat, the solution turns greenish and after- wards blue (Salkowski).^ Acetone gives a red colour with Weyl’s test, but not the subsequent blue. If ammonia be substituted for soda, no red colour is produced by creatinin, which also distinguishes it from acetone. Jaffe’s tes't.^—A little solution of picric acid and a few drops of a dilute solution of caustic soda produces a deep red colour with very dilute solutions of creatinin—i ; 3000. Acetone gives an orange-red with the same reagents. The estimation of creatinin in urine may be made by G. S. John- son’s'* modification of Maly’s process. To a measured amount of urine one-twentieth its volume of a saturated solution of sodium acetate and one-fourth its volume of a saturated solution of mercuric chloride are added. The solution is then immediately filtered and the filtrate is allowed to stand for forty-eight hours. The compound of creatinin and mercury, which has then fallen, is separated and after being distributed in water is decomposed by sulphuretted hydrogen. After filtration from the deposit of mercurous sulphide, the filtrate, which consists of a solution of creatinin hydrochloride, is evaporated down in vacuo ; the residue, dissolved in fifteen times its weight of water, is treated with excess of recently precipitated lead hydrate, and is evaporated in vacuo over sulphuric acid, after which it deposits creatinin in the crystalline form. Allen ® prefers to deal with the mercury .salt by Kjeldahl’s process; the amount of creatinin being deduced from that of the ammonia obtained. Creatinin also forms salts with zinc chloride and silver nitrate. The zinc salt may be obtained by adding a saturated alcoholic solution of zinc chloride to an alcoholic extract of urine which has been * JJcrichte der deutsch. chem. Gesellsc/i., 1878. ^ Zeitschr. f. i>hysiul. Ohem., 1880. » ZeiUchr.f. phymol. Chem., 1886. * Proc. Roy. Soc. Lond., 1888, 1892. » Chemistry of Crine, 1895.’
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