URINE. 113 



3. Solution of sodium hydrate, sp. gr. 1.23 (two-thirds 

 saturated). 



4. Solution of ^ NaOH. 



N 



5. Solution of ^ H 2 S0 4 . 



Detailed Method. 5 or 10 c.c. of urine (according to con- 

 centration) are measured out by a pipette and placed in a 

 long-neck digestion (Kjeldahl) flask. To this is added 10 c.c. 

 of the cone. H 2 S0 4 and one-half of a teaspoonful of potassium 

 sulphate. The mixture is allowed to boil over a sand-bath or 

 wire gauze until the solution becomes water-clear (3 to 6 hrs.). 

 After the flask has cooled, the contents are removed quan- 

 titatively to an Erlenmayer flask (content, 1 liter), using 

 about 400 c.c. of water, and to this solution is added without 

 mixing 40-50 c.c. of the strong NaOH solution. The flask 

 is now quickly connected by means of a rubber cork with a 

 condenser-tube, the other end of which is immersed in a known 



N 

 quantity of ^ H 2 S0 4 (50-200 c.c. according to the estimated 



amount of nitrogen in the urine employed). The vessel 



N 

 used to hold the ^ H 2 S0 4 is usually a small Erlenmayer 



flask. The contents of the large flask are well mixed and 

 a flame placed beneath a wire gauze upon which the flask 

 must rest. After the beginning of ebullition, the boiling 

 should be continued for 45 minutes. This must be regulated 

 so that the NH 3 comes over gradually. At the end of the 

 time the small flask is removed so that the end of the con- 

 denser still remains in the flask but is not in contact with 

 the fluid. It must be held in this position for some minutes 

 to allow the condenser-tube to be washed inside with the 

 water still distilling over, and outside with a stream from 



