n6 Scientific Proceedings (82). 



by the kaolin of nitrogenous substances other than protein. This 

 is most marked with substances of a basic nature, including 

 diamino-acids and ammonia (present as ammonium chloride), 

 and is absolutely quantitative with creatinine, even with amounts 

 several times as great as those in the filtrates from the blood 

 coagula. In the presence of trichloracetic acid, absorption appears 

 to be less marked. The omission of kaolin after the precipitation 

 of the protein by means of trichloracetic acid apparently leads to 

 more accurate figures for the total non-protein nitrogen of the 

 blood. These are about 3 mg. per 100 c.c. of blood higher than 

 those obtained with the use of kaolin. According to Folin and 

 Denis, 1 the results obtained by their meta-phosphoric acid method 

 agree very closely with those obtained by their methyl alcohol 

 method. Since the latter has been shown to give too low results, 2 

 it would seem that meta-phosphoric acid, also, does not yield all 

 the non-protein nitrogen to the filtrate. Gettler and Baker 3 used 

 hydrochloric acid and mercuric chloride for the precipitation of 

 protein and obtained higher values for the non-protein nitrogen 

 of the blood than have other observers. Comparison of the two 

 methods in this laboratory 4 failed, in the few experiments made, to 

 reveal any marked difference in the results obtained by the use of 

 hydrochloric acid and mercuric chloride and by the use of trichlor- 

 acetic acid and kaolin. Gettler and Baker do not direct the use 

 of sodium sulfide or other precipitants for the mercury before the 

 distillation. Unless the mercury is removed or precipitated as 

 sulfide, the results be as much as 50 per cent, too low. 



Although creatinine, under the same conditions, is quanti- 

 tatively removed by kaolin, creatine is not absorbed at all, either 

 from dilute aqueous solution or when added to blood. This 

 offers a method for the estimation of creatine in the blood. The 

 filtrate from the kaolin is treated with a small volume of N 

 hydrochloric acid and evaporated to approximately that volume. 

 (In most of the experiments, a volume of filtrate equivalent to 

 50 c.c. of blood was evaporated to 5 or 10 c.c. after the addition 



1 Folin and W. Denis, Ibid., 1916, 26, 491. 



* I. Greenwald, loc. cit.; Bock, loc. cit. 



8 A. O. Gettler and W. Baker, Ibid., 1916, 25, 210. 



4 1. Greenwald, loc. cit. (page 64) and unpublished expts. 



