120 Decomposition of C]ianainide and Dicyanodiamide 



The above resvilts (plotted in Fig. 5) do not indicate that the 

 ammonification of the dried blood has been appreciably retarded by 

 the dicyanodiamide. It is noteworthy, however, that while the di- 

 cyanodiamide alone has produced no depres.sion of the bacterial numbers, 

 it has caused a temporary check to the multiplication of the organisms 

 b\' the dried blood. It would therefore appear that dicyanodiamide 

 has an adverse action on some of the ammonifying bacteria in the soil; 

 this is also suggested by the slight initial depression of the decomposition 

 of dried blood in the presence of dicyanodiamide. 



The readiness with which cyanamide is converted into nitrate in 

 contrast to the marked resistance shown to this change by dicyanodiamide 

 demonstrates conchisively that the latter is not normally produced 

 from cyanamide in the soil. Further, our results afford no support to 

 the hypothesis of Immendorfl and Kappen as to the occurrence of 

 polymerisation in poor soils. Reference to Table V will show that the 

 production of nitrate from cyanamide has proceeded approximately to 

 the same extent in the poor Woburn soil as in the Eothamsted soil. 



The experiments, on the other hand, provide no indication of any 

 appreciable formation of ammonia from dicyanodiamide in the soil. This 

 fact suggests the possibility of a di-imino formula for dicyanodiamide. 



Experimental. 

 Mustard Pot Experiments. 

 These experiments were carried out concurrently in two series, 

 using Rothamsted soil (a heavy loam) from Great Knott Field, after 

 being passed through a J inch .sieve and thoroughly mixed with 

 10 per cent. sand. The soil contained -1 per cent, calcium carbonate. 

 The nitrogenous dressings^ taken for comparison were: 

 I. Cyanamide. 

 II. Cyanamide 3 parts, 



Dicyanodiamide 1 part. 

 III. Cyanamide 1 part, 



Dicyanodiamide 3 parts. 

 ■ IV. Dicyanodiamide. 



^ The pure cyanamide was applied in the form of fresh nitrolim. in which the calcium 

 cyanamide had undergone practically no change. 



The mixtures of cyanamide and dicyanodiamide were applied respectively in samples 

 of old nitrolim, in which the cyanamide had become transformed into dicyanodiamide to 

 the extent shown by the mixtures in question. 



The dicyanodiamide was prepared in an approximately pure state from a sample of 

 nitrolim and found to contain over 06 per cent, nitrogen as compared with the theoretical 

 GG-6 per cent. 



