THE JOURNAL OF PHARMACOLOGY. 205 



One cubic centimeter of this solution according to Ritter is the equiva- 

 lent of 0.00361 of uric acid. 



(d) Modification of Folin : 10 grammes of ammonium sulphate are added 

 to 100 cubic centimeters of urine, stirring until solution is effected, after 

 which add ammonia water until the mixture is slightly alkaline. Then 

 set aside for at least two hours. After this the precipitate of ammonium 

 urate is transferred to a thin filter and washed free from chlorides by means 

 of a 10 per cent, solution of ammonium sulphate. Then transfer to a 

 beaker or flask, add water to make 100 cubic centimeters and then 15 cubic 

 centimeters of concentrated sulphuric acid, and titrate at once with the 

 N/20 potassium permanganate solution. 



One cubic centimeter of this solution according to Folin is the equiva- 

 lent of 0.00375 of ^fi<^ acid. 



For purpose of greater accuracy a correction of i milligramme is added 

 to the final result. 



The addition of sulphuric acid raises the temperature so that if the titra- 

 tion is carried out at once, no additional heat need be applied. A temper- 

 ature of about 60° C. is most suitable for the reaction. 



As will be noted, Ritter found the uric acid equivalent of one cubic cen- 

 timeter of N/20 potassium, permanganate solution to be 0.00361, while 

 Folin and others found it to be 0.00375. The writer has invariably ob- 

 tained results which closely averaged 0.00375. 



The method yields trustworthy results. 



6, Method of E. Woerner. 



150 cubic centimeters of urine are placed in a beaker and warmed to 40- 

 45° C, then 30 grammes of ammonium chloride are added and the mixture 

 shaken until all is dissolved. After setting aside for >^-i hour the resulting 

 precipitate of ammonium urate is collected on a filter and washed with a io> 

 per cent, solution of ammonium sulphate until free from chlorides. After this 

 the precipitate is dissolved (while on the filter) in hot 1-2 per cent, solution 

 of sodium hydroxide. The filter is washed with hot water and both wash- 

 ings and filtrate are placed in a capsule and heated on a water bath until 

 all ammonia is expelled. The resulting solution (alkaline) of uric acid is 

 now placed in a Kjeldahl flask and treated as in the Kjeldahl method for 

 nitrogen, previously described. The ammonia formed is estimated by 

 means of N/io sulphuric acid. 



I cubic centimeter of N/ 10 sulphuric acid is the equivalent of 0.0042 of 

 uric acid. 



The method is accurate if carefully carried out. 



( To be continued. ) 



