A NOTE ON THE DETERMINATION OF AMMONIA 



IN URINE 



STANLEY R. BENEDICT and EMIL OSTERBERG 



(Department of Chemistry, Cornell University Medical College, 



New York City) 



Since the proposal by Folin^ of his air-current method for the 

 distillation of ammonia, this procedure has been almost universally 

 adopted for estimating ammonia in urine, and in other fluids or 

 mixtures where unstable nitrogenous substances may be present. 

 The accuracyof this method, as employed under ordinary conditions, 

 has never heretofore been questioned. Steel,^ however, in a de- 

 tailed examination of the FoHn method under certain conditions, 

 has called attention to the fact that the alkah employed by FoHn 

 (sodium carbonate) is incapable of completely decomposing mag- 

 nesium ammonium phosphate, and in case the urine contains appre- 

 ciable quantities of this substance, results are low and very irregulär. 



As urines are not infrequently met with which contain magne- 

 sium ammonium phosphate crystals, Steel proposed the modified 

 technique of using one gram of sodium hydroxide and fifteen grams 

 of sodium chloride, in place of the carbonate recommended by Folin. 

 Steel shows conclusively that this mixture of sodium chloride and 

 hydroxide will liberate ammonia quantitatively from magnesium 

 ammonium phosphate, and details a number of experiments to show 

 that substances other than ammonium salts which might be expected 

 to occur in urine are not decomposed by this treatment so as to yield 

 any ammonia. 



Steel also gives figures of numerous determinations made on 

 urines which contained no preformed magnesium ammonium phos- 

 phate crystals, to show that results are identical under such condi- 

 tions, whether sodium carbonate or sodium hydroxide and sodium 

 chloride be used to liberate the ammonia. 



1 Folin: Zeit. f. physiol. Chetn., 37, p. 161 (1902). 



2 Steel: Jour. of Biol. Chem., 8, p, 365 (1910). 



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