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.

    610/660 page 590
    The extraction and estimation of lactic acid in urine is effected in a similar way. (r) The urine (500 c.c.) is evaporated 7 vacuo at 50° to about 100 c.c. and extracted with ether! in the extractor after adding 50 per cent. phosphoric acid with or without the addition of ammonium sulphate. Ammonia is added to the ether extract and the whole evaporated on the water-bath (50 c.c.-20 c.c.) which removes the ether and excess of ammonia. The solution is distilled.in the apparatus described above with 300 c.c. dilute sulphuric acid (the reaction must be strongly acid) until 200 c.c. have passed over. A second distillation using ‘o1N permanganate is then carried out: the titration of this distillate as above gives the quantity of lactic acid (Dapper’s pro- cedure). . (2) The urine (250 c.c.) is treated with phosphotungstic acid, excess of which is removed with baryta, and excess of baryta with carbon dioxide. The solution is evaporated, acidified with phosphoric acid, and the operations described above carried out (Ishihara’s procedure). (3) A simpler procedure by Ryffel ? depends upon the decomposition of lactic acid into acetaldehyde with 50 per cent. sulphuric acid, and the estimation of the acetaldehyde colorimetrically. The method gives results which are about 80 per cent. of the theoretical, if the estimation be effected by titration with bisulphite and iodine. The direct distillation and estimation with bisulphite and iodine is the most conyeni- ent and rapid for routine work. 45 c.c. of concentrated sulphuric acid are added to 40 c.c. urine in a 500 c.c. round bottom flask, the mixture being kept cold during the addition. The flask is connected to a steam generator on the one side and a condenser on the other. A rapid current of steam is passed in; the temperature of the flask as indicated by a thermometer as soon as distillation commences is about 140’, but should be raised by heating to 155° and kept within 2° of this temperature by moderating the current of steam. The decomposition is complete in 30 . minutes after about roo c.c. have been collected. This distillate may be titrated as above or again distilled after making just alkaline and estimated colorimetrically. 1 The ether is purified by shaking with 50 per cent. caustic potash and then with water until the washings are free from alkali.
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