I IO 



Scientific Proceedings (49). 



These various difficulties have led us to return to the precipita- 

 tion of ammonia by means of phosphotungstic acid. Gumlich 1 

 showed originally that the proper conditions for removal of am- 

 monia by 10 per cent, phosphotongstic acid are a strongly acid 

 urine and sedimentation for 24 hours. We have satisfied ourselves 

 that this strength of phosphotungstic acid does not precipitate 

 the mono-amino acids in the concentration usually found in urines. 

 Instead, however, of removing the urea from the phosphotungstic 

 filtrate and the determination of amino-acid nitrogen by difference, 

 as in the original Schondorff-Pfaundler method, or the modifica- 

 tions of it by Krieger and Schmidt, Van Leersum, and others, 

 we remove the phosphotungstic acid by means of tribasic lead 

 acetate and litharge, and titrate for mono-amino acids in the 

 filtrate (after removal of lead) according to the procedure of 

 Henriques and Sorensen. The filtrate is water-clear and free of 

 any constituents which can interfere with the formalin titration. 



Comparison of the Henriques and Sorensen Method with Modified Method. 



Urine 



No. 



H. and S. 



Modified Method. 



Case 1. Pernicious 

 vomiting. 



Case 2. Eclampsia. 



Urine No. i 

 Urine No. 2 

 Urine No. 4 

 Urine No. - 



Urine No. 3 

 Urine No. 7 

 Urine No. 8 

 Urine No. 11 



O.215 gm. NHjN 

 0.434 gni. NHjN 

 0.268 gm. NHjN 

 0.245 gm. NH 2 N 



0.397 gm. NHjN 

 0.157 gm. NH 2 N 

 0-375 gm. NH 2 N 

 0.210 gm. NH 2 N 



0.015 gm. NH 2 N 

 0.048 gm. NH,N 

 0.025 gm. NH 2 N 

 0.023 gm. NHjN 



0.120 gm. NH,N 

 0.035 gm. NH 2 N 

 0.148 gm. NHjN 

 0.155 gm. NHjN 



All the urines contained a large amount of ammonia. It 

 would seem from this comparison that the Henriques and Sorensen 

 method like the Van Slyke method gives results (especially on 

 pathological urines) even after the supposed removal of ammonia 

 which may be quite misleading. 



The following are a few of the results obtained with pure sub- 

 stances. 



A. Pure Solutions: 



1. 20 c.c. iV/20 leucine, purity tested by Kjeldahl and 

 formol titration, added to 5 c.c. N/10 NHiCl < 200 c.c; 

 45 c.c. of final filtrate, titration 2.4, theory 2.28. 



1 Zeitsckr. f. physiol. Chemie, 1893, XVII, p. 13. 



