202 THE JOURNAIv OF PHARMACOLOGY. 



Solution of potassium or sodium sulphide : 15 grammes of potassium or 

 hydrate (or 10 grammes of sodium hydrate) which must be free from 

 nitrates and nitrites, are dissolved in i liter of water. One half of this 

 solution is saturated with hydrogen sulphide, resulting in the formation of 

 acid postassium sulphide. To this add the remaining, unsaturated half, 

 thus forming a solution of potassium sulphide. 



Execution of method : Mix 20 cubic centimeters of the ammoniacal 

 silver nitrate solution and 20 cubic centimeters of the magnesia mix- 

 ture, in a beaker and add enough ammonium hydrate to redissolve the 

 precipitate of silver chloride which has formed. This mixture is then 

 added, stirring constantly, to 200 cubic centimeters of urine, and set aside 

 for y^-i hour. The precipitate which has formed, and which holds the 

 uric acid, is then transferred to a filter and washed two or three times with 

 distilled water containing a small quantity of ammonia. It is not neces- 

 ,sary to remove the small amount of precipitate which adheres to the sides 

 of the beaker. The still moist preciptate is then transferred to the beaker, 

 (by means of a glass rod and wash bottle) in which the first operation 

 (precipitation) was carried out, taking care not to injure the filter. 10 

 cubic centimeters of the potassium sulphide solution are now diluted with 

 an equal volume of water and heated to boiling. The boiling mixture is 

 then passed through the same filter into the beaker containing the pre- 

 cipitate. Wash the filter with a small volume of hot water and then place 

 the beaker on a water bath and heat until the entire precipitate appears 

 black (continued heating at a high temperature must be avoided, as uric 

 acid in alkaline solution, upon excessive and prolonged heating, with free 

 access of air, is converted into uroxonic acid). After cooling filter through 

 the previously used filter, into a capsule and wash the filter with a small 

 quantity of distilled water. To the combined liquids ffiltrate and wash- 

 ings) add about 5 cubic centimeters of diluted hydrochloric acid and con- 

 centrate to about 15 cubic centimeters. Add a few drops of concentrated 

 hydrochloric acid and set aside for 12-24 hours. Crystals of uric acid will 

 then have formed. These are collected on a tared glass-wool or asbestos 

 filter (a paper filter if previously dried at about 110° C, may be used), and 

 washed successively with small quantities of distilled water, alcohol, ether 

 and carbon disulphide, the latter to remove sulphur if it is present. 

 Lastly wash with ether and dry at 100° C, and after cooling, weigh. The 

 difference between the weight of the filter alone, and the weight of the 

 filter with the crystals of the uric acid represents the weight of the latter. 

 The quantity for 24 hours can then readily be calculated. If the crystals 

 of uric acid appear highly colored, dissolve them in hot water with addi- 

 tion of a small quantity of sodium or potassium hydroxide solution. Fil- 

 ter, wash, acidify with hydrochloric acid and concentrate to small volume, 

 after which set aside to crystallize. Then proceed in the same manner as 

 indicated above. 



