134 



Scientific Proceedings (29). 



82 (338) 



On the determination of ammonia, by the Folin method, in 

 urines containing crystalline ammonio-magnesium 

 phosphate. 



By MATTHEW STEEL and WILLIAM J. GlES. 



\Ftom the Laboratory of Biological Chemistry of Columbia Univer- 

 sity, at the College of Physicians and Surgeon s.~\ 



Last fall during the progress of the metabolism research that is 

 described in the abstract immediately preceding this, certain anoma- 

 lous results were obtained in our quantitative determinations of 

 the urinary ammonia. In the earlier periods of that research, 

 urinary ammonia had been determined, by the Folin method, 

 in the urines in duplicate for 38 days, with thoroughly con- 

 cordant results. Shortly after the beginning of a metabolism 

 period, however, during which magnesium sulfate was injected 

 subcutaneously every twenty four hours, the titrations in duplicate 

 (at the conclusion of the Folin process as applied to the daily 

 urines), were strikingly discordant, the disagreements amounting 

 to from 1 to 2 c.c. of ;z/5 KOH per 25 c.c. of urine. 



Our inability to obtain satisfactory duplicate results for urinary 

 ammonia content after the magnesium sulfate treatment, or to ex- 

 plain the analytic discrepancies by any probable fault of technique, 

 led us to make two general suppositions regarding the cause of 

 the analytic disagreements observed : 



1. That magnesium was eliminated into the urines in question 

 in relatively large quantities as ammonio-magnesium phosphate, 

 which separated, in part at least, in typically crystalline masses. 



2. That the crystalline ammonio-magnesium phosphate thus 

 deposited was not thoroughly decomposed by sodium carbonate, 

 as used in the Folin process, whereby ammonia, in variable 

 amounts, remained in its solid form as triple phosphate in the 

 urines under investigation. 



General examination of the urines that gave the anomalous 

 quantitative results for ammonia content showed at a glance that 

 our first supposition was correct — triple phosphate had crystallized 

 in abundance. In separating portions of the urines for analysis, 



