42 Determination of Ammonia in Urine [Oct. 



During the past two years we have made it a practice to run two 

 ammonia determinations on each sample of urine, in one of which 

 sodium carbonate was employed to liberate the ammonia, while in 

 the second one Steel's mixture of sodium hydroxide and sodium 

 Chloride was used. Several hundred determinations hiave been 

 made in this way, including both dog and human urines, and the 

 figures thus obtained do not corroborate those reported by Steel 

 for similar determinations. In every sample of urine analyzed we 

 have obtained slightly higher figures where the hydroxide-chloride 

 mixture was used, than where carbonate was employed. 



There would be little object in including here our large mass of 

 figures obtained in this connection. We may summarize them by 

 stating that normal and pathological urines were used, very few of 

 which were not strongly acid in reaction, and none of which showed 

 the presence of any magnesium ammonium phosphate crystals. 

 Where Steel's hydroxide-chloride mixture was used results were 

 always higher by o.i to 0.8 c.c. of n/io Solutions, amounting usu- 

 ally to from one to seven percent of the total ammonia present, than 

 where carbonate was used. 



The difference in the absolute amount of ammonia obtained by 

 the two processes is obviously small, but the constant results raise a 

 distinct question as to the essential accuracy of the two procedures 

 employed. Does Folin's original process fail to yield all the 

 ammonia from ordinary urines, or does Steel's modification decom- 

 pose some additional urinary constituent in amount sufficient to yield 

 distinctly measurable quantities of ammonia? This question puz- 

 zled US for a long time, but we believe that we have found the cor- 

 rect answer to it in a simple fact which has apparently been over- 

 looked by both Steel and Folin in their work in this connection. 



If carbonate be added according to Folin's directions to a sample 

 of urine, and the aeration process be carried out for a few minutes, 

 and a few drops of the mixture be then examined under the micro- 

 scope, ahiindant masses of magnesium ammonium phosphate crys- 

 tals will he found. We have obtained this result with every sample 

 of urine examined. It can be readily verified by shaking a sample 

 of urine with a little sodium carbonate for about two minutes, and 

 examining the mixture under the microscope. Whether air passes 



