Improvement of the Folin Method. 



127 



67 (405) 



An improvement of the Folin method for the determination of 

 urinary ammonia nitrogen. 



By MATTHEW STEEL. (By invitation.) 



[From the Laboratory of Biological Chemistry of Cobiinbia Univer- 

 sity, at the College of Physicians and Sttrgeons.^ 



In the fall of 1 907, during the progress of a metabolism re- 

 search on "the influence of magnesium sulphate on metabolism," ' 

 anomalous results were obtained in our quantitative determinations 

 of urinary ammonia, whenever the magnesium salt was injected 

 either subcutaneously or intravenously into the animal.^ These 

 anomalous results were found to be due to the facts that the magne- 

 sium was eliminated into the urines in question in relatively large 

 quantities, as ammonio-magnesium phosphate and that the re- 

 sultant deposits of crystalline triple phosphate were not thoroughly 

 decomposed by sodium carbonate, as used in the Folin method, 

 whereby ammonia, in variable amounts, remained in its solid form as 

 triple phosphate in the urines under investigation. We, therefore, 

 sought another method that would liberate all the ammonia from 

 ammonio-magnesium phosphate without producing ammonia from 

 such compounds as urea in the urine. None, however, was found 

 that fulfilled both conditions. Consequently, we were obliged 

 either to devise a new method, or else modify the Folin process, 

 so as to make it liberate the ammonia from triple phosphate. We 

 chose the latter course. 



Our attempt was to find some alkali which would liberate all 

 the ammonia from ammonio-magnesium phosphate and which at the 

 same time would not convert into ammonia any of the amino or 

 imino radicals in the various organic compounds in the urine. 



Varying quantities of milk of lime, baryta water, and sodium 

 hydroxide were added separately to weighed amounts of triple 

 phosphate. These mixtures were aerated as usual. The results 

 obtained made it evident that neither milk of lime nor baryta water, 



1 Steel : These Proceedings, 1908, v, 132 ; Jozirnal of Biological Chemistry, 1908, 

 V, 85. 



^ Steel and Gies : These Proceedings, 1908, v, 134 ; Journal of Biological Chem- 

 istry, 1908, V, 71. 



