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.

    615/660 page 595
    G. B-HYDROXYBUTYRIC ACID. Three methods have been proposed for the estimation of $-hydroxy- butyric acid :— (1) Conversion into crotonic acid by distillation with sulphuric acid. This method originally described by Darmstaedter has not been found entirely satisfactory ; Ryffel described another procedure in 1905.! (2) Conversion into aceto-acetic acid by oxidation and estimation of the acetone by decomposition of the aceto-acetic acid. This method has been worked out by Shaffer. The results are too low by about 10 per cent. as was shown later by Shaffer and Marriott? and also by Kennaway.* The error appears to be constant so that the method can be employed if ro per cent. be added to the values obtained. In Urine. Shaffer and Marriott’s procedure is as follows :— 25 to 100 cc. of urine (50 cc. average) are placed in a 500 c.c. measuring flask containing 200-300 c.c. of water. A volume of basic lead acetate solution (U.S.P) equal to ‘the volume of urine is added and the liquids well mixed. A volume of strong ammonia water equal to half of the basic lead acetate solution is poured in and the volume made up to 500 c.c. with water. ‘The contents are mixed and filtered after standing for a few minutes through a fluted filtered paper. This-treatment removes glucose and pigments. 200 c.c. of the filtrate are measured out into an 800 or 1000 c.c. round bottom flask, diluted to about 600 c.c. and 15 c.c. of con- centrated sulphuric acid are added together with some talc or a piece of por- celain. ‘The solution is distilled and 200 c.c. distillate collected in another 800 c.c. flask, the end of the condenser being placed under some water in this receiver. In order that the volume in the flask does not become less than 400-500 c.c. water is occasionally added through a tap funnel fitted in the neck of the flask. This distillate contains acetone from aceto-acetic acid. It is redistilled after adding 10 c.c. of ro per cent. sodium hydroxide solution and the distil- late collected and titrated as described under aceto-acetic acid. The residue of urine is again distilled and at the same time oxidised with potassium bichromate, of which *s to 1‘o gm. is generally sufficient ; if the liquid turns green more will be required. ‘The volume must be kept be- tween 400-500 c.c. It is most convenient to keep a 1o per cent. solution of bichromate and to dilute 10 c.c. to 100 c.c. for each determination. 20 c.c. of the diluted solution are added through the tap funnel and alternately water and ro c.c. portions of bichromate are added every 15-20 minutes. If the liquid turns green the bichromate must be added at shorter intervals. The oxidation and distillation is continued at a moderate rate for 2-3 hours. The distillate is collected in a rooo c.c. round bottom flask as before and redistilled after adding 10 c.c. of 10 per cent. sodium hydroxide and 25 c.c. of 3 per cent. hydrogen peroxide, the heating being cautious until the hydrogen peroxide is decomposed. Acetaldehyde obtained by the oxidation of lactic acid is removed by this second distillation. This distillate is titrated with iodine and thiosulphate. 1 c.c. ‘IN iodine solution = 0'001793 gm. hydroxybutyric acid. 1]. Physiol., 32, Proc. ivr. 2 J. Biol. Chem., 1913, 16, 265. ' 3 Biochem. J., 1914, 8, 230. 38 *
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