714 



PHYSIOLOGICAL CHEMISTRY. 



urea, and the necessity of neutralizing the acid radicals of the urine 

 which are normally in excess of the basic radicals. Accordingly, 

 the urinary ammonia is increased when the urea-forming apparatus is 

 deficient /. e., in certain disease of the liver. It is likewise increased 

 in the presence of an abnormal excess of acid e. g., the acidosis of 

 diabetes and of the pernicious type of vomiting in pregnancy. As 

 the absolute amount of ammonia in the urine is greatly modified by 



FIG. 74. 



Doremus' ureometer. 



the amount of total nitrogen, it is necessary to estimate the amounts 

 of each in order to obtain the important point the ammonia fraction 

 of the total nitrogen. 



Estimation of ammonia in the urine. The ammonia in a measured 

 amount of urine is set free by the addition of sodium carbonate. By 

 means of a suitable closed system of apparatus and an ordinary suc- 

 tion pump a current of air is carried through this mixture and 

 allowed to bubble up through a measured amount of sulphuric acid. 

 At the end of an hour and a half all of the ammonia will have been 



