60 University of California Publications in Agricultural Sciences [Vol. 1 



These results show a slight loss where large amounts of nitrate 

 were present, but the same also holds true above, as an exami- 

 nation of the foregoing tables will indicate. Therefore the losses, 

 which are also in part explained above, are not to be attributed 

 to the presence of excessive amounts of soluble organic materials. 

 Besides, the losses brought about for the reasons indicated are 

 of no serious practical import, since most soils seldom contain 

 more than from 15 to 20 milligrams of nitrogen per 100 grams 

 of soil. 



The Time Required for Complete Reduction at a 

 Temperature of 20°-22° C. 



That the time required for complete reduction should be 

 accurately ascertained at a given temperature is obvious. The 

 results given below are averages of analyses carried on simul- 

 taneously. 



TABLE V 



The Effect of Time ox the Process of Eeductiox at Constant 

 Temperature (20°'22'' C.) 



Hours 1 2 Ms 4 6 8 9 10 11 12 15 24 



Nitrate N Nitrate X recovered 



added Mgs. 



MgS. r ^' 



100 19.04 33.88 46.20 .5.5.02 89.74 93.10 96.53 97.90 97.44 98.42 95.20 

 50 19.18 22.05 31.36 36.82 46.76 47.18 49.14 49.10 48.86 49.42 49.42 

 25 14.35 17.71 19.00 20.79 23.94 23.94 24.50 24.50 24.50 24.50 



In all of these samples 0.2 per cent of XaCl was present. A 

 study of this data shows 11 to 15 hours to be the optimum time 

 limits for reduction at 20°-22° C. A longer time results in a 

 slight loss of ammonia from the solutions containing the larger 

 amounts of nitrogen, while less than 11 hours is too short to effect 

 complete reduction. 



The Effect of Temperature on the Time Necessary for 



Reduction 



Temperature is of vital importance, both in the accuracy of 

 the determination and also on the time necessary for complete 

 reaction. This is borne out by the following table. 



