114 LABORATORY WORK IN PHYSIOLOGICAL CHEMISTRY. 



the wash-bottle. Then turn oft the flame. The amount of 



N N 



^-r acid still unneutralized is titrated with ^ NaOH. The 



difference between this and the amount originally placed 



N 



in the flask will represent the amount of the ^ acid neu- 

 tralized by the NH 3 which was distilled over. 



N 



1 c.c. -JQ H 2 S0 4 = 0.0014 grm. N., from which may be 



calculated the quantity of N. in the 10 c.c. used and then 

 in the 24-hour sample. 



UREA (HUFFNER'S METHOD). 



For the determination of urea, the following method, 

 whose use has become almost universal, seems sufficiently 

 accurate to warrant its continuance in favor. The rapidity 

 with which it can be performed offsets the disadvantage 

 of the mere approximation of results and renders it pre- 

 eminently suited for clinical purposes. 



Only about 92 per cent of the nitrogen of the urea actually 

 present in the urine is obtained as a gas, although the theoret- 

 ical reaction is quantitative, 



CO/ 



NH 2 



+ 3NaOBr= N 2 +C0 2 +2H 2 0+3NaBr 

 NH 2 



(see experiment (e) under Urea), but the deficit is partially 

 diminished by the fact that other substances (e.g., uric acid) 

 also yield up some of their nitrogen as a gas by the decompo- 

 sition with hypobromite. 



_ The more accurate methods (Morner-Sjoqvist or Folin's) 

 will be demonstrated. 



