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.

    572/660 page 552
    Uric Acid. In 1892 it was shown by Hopkins that uric acid could be com- pletely precipitated from urine as ammonium urate by saturating the urine with ammonium chloride. Its amount was estimated by convert- ing this into uric acid by the action of hydrochloric acid, dissolving the latter in sodium carbonate and titrating with standard permanganate solution. Very accurate results are obtained by Folin and Schaffer's one most co nmonly employed. For this method the following reagents are required :— (1) Uranium acetate mixture. A solution of ammonium sulphate, monium sulphate, 5 gm. uranium acetate, and 60 c.c. 10 per cent. acetic acid are dissolved in 650 c.c. water. The volume of this solution is almost exactly 1000 c.c. (2) IO per cent. ammonium sulphate solution. (3) ‘o5N potassium permanganate solution made by dissolving 1°58I1 gm. pure potassium permanganate in 1 litre of water (1 cc. = 0°00375 gm. uric acid). Procedure. 200 c.c. of urine are measured out with a pipette into a 500 cc. flask and 50 c.c. of the uranium acetate mixture are added. The solutions:are mixed and allowed to stand for about half an hour so as to allow the precipitate to settle. This precipitate contains a mucoid and washing of the ammonium urate precipitate very slow. The supernatant liquid is filtered off through a dry filter into a dry vessel ; 125 c.c.(=100 c.c. urine) of this are measured out with pipettes into a beaker; 5 c.c. of concentrated ammonia are added and mixed and it is allowed to stand covered with paper for 12-24 hours. The supernatant liquid is carefully decanted upon a filter, the pre- cipitate of ammonium urate is washed on to the filter with 10 per cent. ammonium sulphate solution and. washed once or twice with the same reagent to remove the chlorides as completely as possible. The filter is removed from the funnel, opened, and with a fine stream of water the ammonium urate precipitate is washed into a beaker or flask. To the ammonium urate precipitate, suspended in about 100 c.c. of water, 15 c.c. of concentrated sulphuric acid are added and it is titrated at once without cooling with ‘o5N potassium permanganate until a pink colour is first seen throughout the solution (cf. p. 292). The result is calculated as follows :— I c.c. °05N KMnO, = 0°00375 gm. uric acid, oe atop R = x X 0°00375 gm. uric ‘acid, but since ammonium urate is slightly soluble a correction of 3 mem. for every 100 c.c, of urine used must be added. The result is :— the amount in the 24 hours’ quantity is calculated.
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