URINE: QUANTITATIVE ANALYSIS. 



FIG. 123. 



absorption apparatus to the one just described is attached to the 

 other side of the aerometer cylinder, thus insuring the passage of 

 ammonia-free air into the cylinder. With an 

 ordinary filter pump and good water pressure the 

 last trace of ammonia should be removed from 

 the cylinder in about one and one-half hours. 1 

 The number of cubic centimeters of the -^ sul- 

 phuric acid neutralized by the ammonia of the 

 urine may be determined by direct titration with 

 f-Q sodium hydroxide. 



This is one of the most satisfactory methods 

 yet devised for the determination of ammonia. 



Calculation. Subtract the number of cubic 

 centimeters of -^ sodium hydroxide used in the 

 titration from the number of cubic centimeters 

 of y^- sulphuric acid taken. The remainder is 

 the number of cubic centimeters of -3^5- sulphuric 

 acid neutralized by the NH :J , of the urine. I c.c. 

 of y\ sulphuric acid is equivalent to o.ooz/ gram 



FOLIN IMPROVED AB- 

 SORPTION TUBE. 



of NH 3 . Therefore if y represents the volume 



of urine used in the determination and y' the 



number of cubic centimeters of T \ sulphuric acid neutralized by the 



NH B of the urine, we have the following proportion : 



y : 100 : : y' X 0.0017 : x (percentage of NH 3 in the urine examined). 



Calculate the quantity of NH 3 in the twenty-four hour urine 

 specimen. 



VI. Nitrogen. 



Kjeldahl Method. 2 The principle of this method is the con- 

 version of the various nitrogenous bodies of the urine into ammon- 

 ium sulphate by boiling with concentrated sulphuric acid, the subse- 

 quent decomposition of the ammonium sulphate by means of a fixed 

 alkali (NaOH) and the collection of the liberated ammonia in an 

 acid of known strength. Finally, this partly neutralized acid solu- 



1 With any given filter pump a " check " test should be made with urine or 

 better with a solution of an ammonium salt of known strength to determine how 

 long the air current must be maintained to remove all the ammonia from 25 c.c. 

 of the solution. 



2 There are numerous modifications of the original Kjeldahl method; the one 

 described here, however, has given excellent satisfaction and is recommended 

 for the determination of the nitrogen content of urine. 



