Apr. 5, 1924 
Studies with Cyanamid 
43 
aliquot of soil extract 10 cc. of a freshly prepared neutral 2 per cent water extract 
of Jack-bean flour. After standing for one hour at room temperature the solu¬ 
tion is made acid with a measured excess of standard acid, aerated for 5 minutes 
to drive off carbon dioxid and titrated. The acid used up is a measure of the 
ammonia formed from the urea. Blanks on soil extract alone showed no inter¬ 
ference in this method. 
EXPERIMENTAL RESULTS 
PART I.—AMMONIFICATION AND NITRIFICATION OF CYANAMID AND 
UREA 
COMPARATIVE RATES OF NITRIFICATION OF CYANAMID, UREA, AND AMMONIUM 
SULPHATE 
The soil used for these experiments was obtained fresh, then sieved and-air- 
dried. An analysis of the dry soil showed 0.56 mgm. of nitrate nitrogen per 
Fig. 1—Diagram showing the rates of nitrification of cyanamid, urea, and ammonium sulphate. 
100 gm. of soil. One gm. of powdered calcium carbonate was added to each 
100 gm. of soil in order to insure neutrality. The figures given in Table III are 
the averages of duplicate determinations. 
Considering the results in Table III, which are shown diagrammatically in 
figure 1, it will be observed that there was no very great difference between the 
rates of nitrification of ammonium sulphate and urea, the slight difference being 
in favor of the latter material. The maximum conversion of 87.8 per cent for 
ammonium sulphate was reached in 42 days, while with urea the maximum, 
91.9 per cent, was reached in 28 days. 
