332 PHYSIOLOGICAL CHEMISTRY 



33'. Repeat the process described in 32, omitting the addition 

 of oxalate. Consider the result in connection with your ob- 

 servations in the preliminary experiments under section 31. 



Total Nitrogen. 



34. Determine the total nitrogen in 5 c.c. of urine by the 

 Kjeldahl method and calculate the 24-hour quantity. 



Ammonia. 



35. Folin Air Current Method. The most satisfactory method 

 for determining ammonia in urine is that of Folin. This con- 

 sists in measuring a given volume of urine into a tall cylinder 

 (B) fitted with a two hole rubber stopper. Through one hole 

 passes a glass tube reaching to the bottom of the cylinder for 

 the admission of compressed air. Through the second hole a 

 glass tube leads into a receiving flask (C) provided with a Folin 

 absorption tube. In this flask is placed a measured volume of 

 N/10 acid, and enough distilled water to cover the holes in the 

 Folin absorption tube. The ammonia is liberated from the urine 

 by adding solid sodium carbonate. 



Into the receiving flask measure 20 c.c. N/10 acid and add 

 two drops of alizarine red. Add enough distilled water to 

 well cover the bell of the Folin absorption tube. Into the tall 

 cylinder measure 25 c.c. of urine. Cover with a thin layer of 

 kerosene to prevent foaming. Make sure that all connections 

 are tight and everything in readiness to start the air current. 

 The compressed air should be run through 10% H 2 S0 4 to 

 remove possible ammonia. Add about 1 gm. of anhydrous 

 sodium carbonate to the urine and stopper the cylinder at once. 

 Pass a fairly rapid stream of air through the apparatus, being 

 careful not to blow the contents of the cylinder into the acid 

 bottle. A loose plug of cotton may be introduced in the path 

 of the air passing from urine to acid by including a calcium 

 chloride tube in the circuit. This will prevent the blowing 

 over of any particles of carbonate. Run the air current for 

 1% hours. Disconnect the acid container, rinse and remove the 



