34 METHODS FOR THE ANALYSIS OF URINE 



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

 is equivalent to the number of cubic centimeters of N/10 sul- 

 phuric acid, neutralized by the ammonia of the urine. One c.c. 

 of N/10 sulphuric acid is equivalent to 0.0014 gm. of nitrogen. 

 Therefore, if y represents the volume of urine used in the deter- 

 mination and y' the number of cubic centimeters of N/10 sul- 

 phuric acid neutralized by the ammonia of the urine, we have 

 the following proportion: 



y : 100 : y'X 0.0014 : x (percentage of nitrogen in the urine 

 examined). 



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

 specimen. 



A SIMPLIFIED KJELDAHL METHOD FOR URINE 1 



Principle. The principle is identical with that for the ordinary 

 Kjeldahl determination. 



Procedure. Transfer 5 c.c. of undiluted urine to a 300 c.c. 

 Kjeldahl flask (Pyrex). Add 5 c.c. of the phosphoric-sulphuric 

 acid mixture, also 2 c.c. of 10 per cent ferric chloride solution and 

 four to six small pebbles to prevent bumping. Boil in a hood 

 over a micro-burner. Boil vigorously. In three to four minutes 

 the foam which forms at first will entirely disappear and the 

 flask becomes filled with dense white fumes. When this stage 

 is reached (but no earlier) cover the mouth of the flask with a 

 small watch glass and continue the vigorous heating for two 

 minutes. At the end of two minutes dilute urines will already 

 be green or blue, and concentrated urines will be a light straw 

 yellow, the black carbonaceous matter will be completely 

 destroyed. The flame should then be turned very low and the 

 gently boiling process should be continued for two minutes, making' 

 a total boiling period of four minutes, counting from the time 

 the watch glass was put in place. Remove the flame and let 

 the flask cool for four to five minutes. At the end of four, or 

 not more than five minutes, add first 50 c.c. of water, then 15 c.c. 

 of saturated sodium hydroxide (50 to 55 per cent), and connect 

 the flask promptly, by means of a rubber stopper and ordinary 



1 Folin: Jour. Biol. Chem., 1919, 38, 461. 



