46 Studies of Aeration Methods [Oct 



of the Polin method that will yield all the ammonia (nitrogen) 

 from ammonio-magnesiiim phosphate in the urine without produc- 

 ing ammonia from non-ammoniacal radicals" (p. 83). 



The modification Steel and Gies had in mind when this inten- 

 tion was expressed, was, as their preliminary results had suggested, 

 the Substitution of caustic alkali for sodium carbonate. For some 

 time, thereafter, Steel continued the work along these lines, in this 

 laboratory, and found^ that 0.5-1 gram of sodium hydroxid plus 

 about 15 grams of sodium chlorid may be substituted for the sodium 

 carbonate and sodium chlorid in the Folin method, for the com- 

 plete ejection of ammonium from crystalline ammonio-magnesium 

 phosphate in urine, without producing ammonia from amino radicals. 



This modified Folin method has been in regulär use in this 

 laboratory ever since, for the determination of urinary ammonia, 

 because it appears to be quite as efficient as the original Folin proc- 

 ess in all respects and is certainly much more accurate when an 

 appreciable quantity of ammonio-magnesium phosphate is present. 



Folin's criticism of the proposed modification. Shortly 

 after the publication of this finding, Folin wrote, in part, as fol- 

 lows:^ "The possible occurrence of minute amounts of ammonium 

 magnesium phosphate hardly Warrants the Substitution of sodium 

 hydrate and sodium chloride for sodium carbonate and sodium Chlo- 

 ride in all ammonia determinations as recommended by Steel. 

 There can scarcely be any doubt but ( !) that the carbonate is the 

 safer reagent, and therefore to be preferred, unless weightier 

 reasons can be found against it than the possible ( !) occurrence of 

 traces of the triple phosphate." 



In expressing these opinions, Folin appears to have ignored the 

 data which showed that ammonia was not evolved, by the NaOH- 

 NaCl process, from such urinary constituents as allantoin, creatin, 

 Creatinin, glycocol, guanin, hippuric acid, leucin, taurin, tyrosin, 

 Urea, uric acid. The only support that Folin published for his 

 opinion against the use of sodium hydroxid appears to be the fol- 

 lowing (p. 497) : "The use of sodium hydrate in connection with 

 the air current method for determining ammonia in urine was advo- 



3 Steel : Jour. Biol. Cheni., 1910, viii, p. 365. 

 * Folin: Jour. Biol. Chem., 1910, viii, p. 497. 



