CYANAMID — MANUFACTURE, CHEMISTRY AND USES 47 



Series I, yet in the dilute solutions the transformation is very 

 slow. 



The above experiment shows that the cyanamide does not 

 react with other soluble substances of the soil, for in such case 

 the maximum activity should occur in dilute solutions ; but its 

 conversion is at a maximum when the greatest amount of 

 cyanamide is enabled to come in contact with the solid sur- 

 faces of the soil particles. This condition is obtained when 

 for a given quantity of cyanamide the amount of liquid is a 

 minimum, for then the liquid film about the solid soil particles 

 is its thinnest, the cyanamide is closest to the soil, and the 

 forces of surface tension are at their maximum. 



INiXUENCE OF AERATION. 



In order to determine whether oxidation plays any part in 

 the phenomena, an apparatus was arranged so that a current 

 of air in one case and a current of hydrogen in another could 

 be conducted over the samples of soil treated as before with 

 4.2 per cent, cyanamide solution. The treatment lasted for six 

 days, a portion of the sample being withdrawn in three days. 

 The following results were obtained : 



Quantity cyanamide present 



Initial , « » Per cent. 



quantity after after Cyanamide converted in 



cyanamide 3 days 6 days , ' > 



Mg. Mg. Mg. 3 days 6 days 



Air 168.0 iio.o 22.0 34.0 86.0 



Hydrogen.. 168.0 114.0 46.0 32.0 72.0 



There is practically no difference in the amounts of conver- 

 sion in 3 days, and not a great deal of difference between the 

 amounts of conversion in 6 days. The results do not differ 

 enough so that it can be said that oxidation plays any appreci- 

 able part in the change. The fact, therefore, that in all of the 

 preceding experiments the tubes were stoppered with cork and 

 sealed with paraffin to prevent evaporation of water could not 

 at any rate increase the conversion. 



