Aids to the analysis of food and drugs / by T.H. Pearmain and C.G. Moor.
- Thomas Hames Pearmain
- Date:
- [1895]
Licence: Public Domain Mark
Credit: Aids to the analysis of food and drugs / by T.H. Pearmain and C.G. Moor. Source: Wellcome Collection.
Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.
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![The Determination of Uric Acid. - Uric acid is detected in urine by the addition of one-fifth of its volume of concentrated hydrochloric acid. The uric acid will deposit after standing some hours in the form of reddish- brown crystals. Uric acid can be estimated by Haycraft's method which is based on the fact that uric acid combines with silver as silver urate, which is practically insoluble in water ammonia, or acetic acid, but perfectly soluble in nitric acid. The estimation of the uric acid depends upon the titration of the silver, which is combined by Volhard's method. The necessary solutions are : (a) A centinormal solution of ammonium thiocyanate standardized by a silver solution of known strength ] cc of this=0-00168 gramme uric acid. (b) An ammoniacal silver solution. 5 grammes silver nitrate in about 100 cc. of water, precipitated and re- aissolved in ammonia to a clear solution. (c) Ferric indicator. A saturated solution of iron alum (d) Pure nitric acid. 25 cc. of the urine is placed in a small beaker, together with about 1 gramme of sodium bicarbonate, and two or three drops of strong ammonia. This precipitates ammonio-magnesic phosphate, and prevents reduction of silver ; 1 to 2 cc. of ammoniacal silver solution is then added, which at once precipitates the silver urate The mixture is now placed on a filter, and washed until the washings show no trace of silver on testing with salt solution. The precipitate is then dissolved in a few cc.'s of nitric acid, washed into a flask, a few drops of the ferric indicator added, and then titrated with the ammonium thiocyanate solution until a permanent red colour just ap- pears. The number of cc.'s used, multiplied by 0 00168X4, gives the percentage of uric acid in the sample. (Sutton' ' Vol. Analysis.') Normal urine contains from 0'3 to 0'7 per cent, uric acid. The Detection of Bile.— Pettenkofer's :7Vs£—Equal parts of the urine and sulphuric acid are mixed ; after cooling the tube in cold water, a little powdered white sugar is then added ; after well mixing, the tube is slightly warmed. If a reddish or violet coloration due to the liberation of cholalic acid is seen, bile is undoubtedly present.](https://iiif.wellcomecollection.org/image/b21508975_0138.jp2/full/800%2C/0/default.jpg)
