674 URINE. 



Preparation of Uric Acid from Urine. Filtered normal urine is treated 

 with 20-30 cc. of 25-per cent hydrochloric acid for each liter of urine. 

 After forty-eight hours collect the crystals and purify them by redis- 

 solving in dilute alkali, decolorizing with animal charcoal and repre- 

 cipitating with hydrochloric acid. Large quantities of uric acid are 

 easily obtained from the excrement of serpents by boiling it with 

 dilute caustic potash (5-per cent) until no more ammonia is developed. 

 A current of carbon dioxide is passed through the filtrate until it barely 

 has an alkaline reaction; dissolve the separated and washed acid potas- 

 sium urate in caustic potash, and precipitate the uric acid in the nitrate 

 by addition of an excess of hydrochloric acid. 



Quantitative Estimation of Uric Acid in the Urine. As the older 

 method suggested by HEINTZ, even after recent modifications, gives 

 inaccurate results, it will not be considered here. 



SALKOWSKI and LUDWIG'S J method consists in precipitating the uric 

 acid, by silver nitrate, from the urine previously treated with magnesium 

 mixture, and weighing the uric acid obtained from the silver precip- 

 itate. Uric acid determinations by this method are often performed 

 according to the suggestion of E. LUDWIG, which requires the follow- 

 ing solutions: 



1. An AMMONIACAL SILVER-NITRATE SOLUTION, which contains in 1 liter 26 

 grams of silver nitrate and a quantity of ammonia sufficient to redissolve com- 

 pletely the preciptate produced by the first addition of ammonia. 2. MAGNE- 

 SIA MIXTURE. Dissolve 100 grams of crystallized magnesium chloride in water, 

 add ammonia until the liquid smells strongly of it, and enough ammonium 

 chloride to dissolve the precipitate ; then dilute the solution to 1 liter. 3. SODIUM 

 SULPHIDE SOLUTION. Dissolve 10 grams of caustic soda which is free from nitric 

 acid and nitrous acid in 1 liter of water. One half of this solution is completely 

 saturated with sulphuretted hydrogen and then mixed with the other half. 



The concentration of the three solutions is so arranged that 10 cc. 

 of each is sufficient for 100 cc. of the urine. 



100-200 cc., according to concentration, of the filtered urine, freed 

 from protein (by boiling after the addition of a few drops of acetic acid), 

 are poured into a beaker. In another vessel mix 10-20 cc. of the silver 

 solution with 10-20 cc. of the magnesia mixture and add ammonia, 

 and when necessary also some ammonium chloride, until the mixture 

 is clear. This solution is added to the urine while stirring, and the mix- 

 ture allowed to stand quietly for half an hour. The precipitate is col- 

 lected on a filter, washed with ammoniacal water, and then returned to 

 the same beaker by the aid of a glass rod and a wash-bottle, without 

 destroying the filter. Now heat to boiling 10-20 cc. of the alkali-sulphide 

 solution, w r hich has previously been diluted with an equal volume of 

 water, and allow this solution to flow through the above filter into the 

 beaker containing the silver precipitate; wash with boiling water, and 

 warm the contents of the beaker on a water-bath for a time, stirring 

 constantly. After cooling, filter into a porcelain dish, wash the filter 

 with boiling water, acidify the filtrate with hydrochloric acid, evaporate 



1 Salkowski, Virchow s Arch., 52; Pfliiger's Arch., 5; Salkowski, Laboratory Manual 

 of Physiol. and Path. Chem., translated by Orndorff, 1904; Ludwig, Wien. med. 

 Jahrbuch, 1884, and Zeitschr f anal Chem , 24. 



