AMMONIA 43 



come into intimate contact with the acid in the absorption flask. 

 In order to exclude any error due to the presence of ammonia 

 in the air a similar absorption apparatus to the one just described 

 is attached to the other side of the aerometer cylinder, thus insur- 

 ing 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. The number of cubic centimeters of the N/10 

 sulphuric acid neutralized by the ammonia of the urine may be 

 determined by direct titration with N/10 sodium hydroxide. 



Steele l has suggested a modification for use on urines containing 

 triple phosphate sediments. In this modification 0.5 to 1.0 gm. 

 of NaOH and about 15 gms. of NaCl are substituted for the 

 Na2COs of the Folin method. The use of sodium hydroxide 

 and chloride instead of carbonate has also been recommended 

 by other workers as a general procedure, inasmuch as triple phos- 

 phate crystals are almost always formed on adding sodium car- 

 bonate and these are decomposed with some difficulty by sodium 

 carbonate but readily by the hydroxide. It has not been shown 

 that the use of sodium hydroxide in this manner brings about the 

 decomposition of any other urinary nitrogen compounds. 



Calculation. Subtract the number of cubic centimeters 

 of N/10 sodium hydroxide used in the titration from the number 

 of cubic centimeters of N/10 sulphuric acid taken. The remainder 

 is the number of cubic centimeters of N/10 sulphuric acid neu- 

 tralized by the NHa of the urine. One c.c. of N/10 sulphuric 

 acid is equivalent to 0.0017 gm. of NHs. Therefore if y repre- 

 sents the volume of urine used in the determination and y' the 

 number of cubic centimeters of N/10 sulphuric acid neutralized 

 by the NHs of the urine, we have the following proportion: 



y : 100 :: y'X 0.0017 : x (percentage of NHs in the urine 

 examined) . 



Calculate the quantity of NHs in the twenty-four-hour urine 

 specimen. 



1 Steele: Jour. Biol. Chem., 1910, 8, 365. 



