54 Vniversiiy of California Publications in Agricultural Sciences [Vol. 1 



down to about half their original volume to drive off ammonia, 

 the residues washed into 125 c.e. Jena test tubes, diluted to 

 100 c.c, and a strip of aluminum (about 150 X 6 X -4 mm., 

 weighing approximately one gram) added to each. The tubes 

 are then stoppered with one-hole rubber stoppers carrying bent 

 glass tubes, each of which has been drawn out to a fine capillary 

 tip. The solutions are allowed to remain in the tubes from 11 

 to 14 hours at a constant temperature of from 20° to 22° C. 

 (about our laboratory temperature). In case of large amounts 

 of nitrogen the temperature is of prime importance, a lower 

 temperature giving incomplete reduction in the above mentioned 

 time, while a higher temperature may induce a considerable loss 

 of ammonia. After reduction the contents of the test tubes are 

 washed into distilling flasks, about 300 c.c. of distilled, ammonia- 

 free water is added, and the ammonia distilled off and caught in 

 N/10 HCl, the excess of acid being titrated against N/10 NH^OH. 



We run 24 or 36 determinations simultaneously, avoiding a 

 loss of time by allowing the reduction to take place over night, 

 either in an incubator kept at 20°-22° C, or when temperature 

 conditions are right, in the laboratory. 



The cut below shown is a photograph of a rack which the 

 writer had made for the purpose of holding 36 of the large test 

 tubes while reduction was taking place. The holes are all num- 

 bered, thus doing away with the necessity of marking the glass 

 tubes, the determinations being run in rotation. 



