42 METHODS FOR THE ANALYSIS OF URINE 



digestion period transfer the contents of the test-tube to a 200 c.c. 

 volumetric flask, diluting to a volume of 150 c.c. Add 1 mg. of 

 nitrogen in the form of ammonium sulphate to another volu- 

 metric flask. To this standard add 1 c.c. of the urease solution 

 and dilute to about 150 c.c. Then add 20 c.c. of the Nessler 

 solution prepared according to the directions given on page 87. 

 Dilute to volume and make the color comparison. The ammonia 

 nitrogen, is, of course, included in the figure obtained. 



Remarks. This determination may be made in urines very 

 rich in albumin. Because of the extremely low nitrogen content 

 of the urease preparation, it is not really essential that the 

 urease should also be added to the standard ammonia solution, 

 but it is added simply as a precaution against the possible occur- 

 rence of less pure urease preparations. 



AMMONIA 



Folin's Method 1 



Principle. The ammonia of the urine is set free by the addi- 

 tion of an alkali and this ammonia is then carried over by an 

 air current into a flask containing a measured amount of standard 

 acid. The excess is then titrated. The necessity for distillation 

 is avoided. 



Procedure. Place 25 c.c. of urine in an aerometer cylinder, 

 30 to 40 cm. in height, add about 1 gm. of dry sodium carbonate 

 and introduce some crude petroleum to prevent foaming. Insert 

 into the neck of the cylinder a rubber stopper provided with two 

 perforations, into each of which passes a glass tube, one of which 

 reaches below the surface of the liquid. The shorter tube 

 (10 cm. in length) is connected with a calcium chloride tube filled 

 with cotton, and this tube is in turn joined to a glass tube extend-, 

 ing to the bottom of a 500 c.c. wide-mouthed flask which is intended 

 to absorb the ammonia and for this purpose should contain 20 c.c. 

 of N/10 sulphuric acid, 200 c.c. of ammonia-free distilled water 

 and a few drops of an indicator (alizarin red or Congo red). To 

 insure the complete absorption of the ammonia the absorption 

 flask is provided with a Folin unproved absorption tube which 

 is very effective in causing the air passing from the cylinder to 

 1 Folin: Am. Jour. Physiol., 1915, 13, 45. 



