. CONTRIBUTIONS FROM THE WISLEY LABORATORY. 615 



extremely hygroscopic. The following table shows how very readily it 

 absorbs water from the air when exposed in a saturated atmosphere as 

 compared with calcium cyanamide and nitrate of soda. 



[To arrive at these figures small quantities of the substances 

 were accurately weighed out into small open dishes standing over water 

 under bell glasses. They were thus under the best condition for 

 absorbing water. The dishes and their contents were re-weighed 

 at the end of forty-eight hours, and again later. The results given are 

 the average of several weighings.] 



TABLE VI. 

 Absorption of Water from Saturated Air. 





1 



Original weight 



Weight at end of 

 forty-eight hours 



Weight at end of one 

 hundred and twenty 

 hours 



Calcium cyanamide . 



100 



102-7 



158-7 



Nitrate of soda . 



100 



105-8 



226-9 



Nitrate of lime . 



. J 100 



115-6 



247-2 



The nitrate of lime thus takes up water very readily indeed from 

 the air, and we found this property made it very difficult to sow, since 

 it quickly caked and became sticky, while, when stored under condi- 

 tions that caused no perceptible change in nitrate of soda, the bulk 

 took up sufficient water to cause it to cake, and, later, some was lost 

 by solution in water absorbed from the air. It was for this reason 

 that it was used in one season only. No doubt if it were used 

 immediately the barrel was opened, the latter having been kept in a 

 dry place until used, it might be applied readily enough ; but in gardens 

 it is seldom necessary to use a barrel at a time.* 



The average percentage of nitrogen in commercial nitrate of lime 

 is 13, and, as we have pointed out above, it supplies nitrogen in a 

 readily available form, and is, nitrogen for nitrogen, of equal value' 

 with nitrate of soda. 



As nitrate of soda contains on an average 15'7 per cent, of nitrogen, 

 the price of nitrogen of lime per cwt. should be less than that of nitrate 

 ■ of soda in proportion to the amount of nitrogen contained. 



If superphosphate is mixed with nitrate of lime it should be sown 

 immediately, otherwise undesirable reactions will be set up. 



Calcium Cyanamide or Nitrolim. — This substance is in the form of 

 a very fine dry black powder, consisting of about 57 per cent, of the 

 pure calcium cyanamide, 14 per cent, of free carbon, and 21 per cent, 

 of caustic lime. Small quantities of sulphur, phosphorus, silicon, 

 &c., are also present. The nitrogen in the .manure may be as high as 

 20 per cent., but the samples used in the foregoing experiment con- 

 tained a little over 17 per cent. 



As shown in Table YL, the cyanamide takes up water slowly, but 

 not to such an extent under ordinary conditions of storage as to 

 interfere in any way with its use. 



*^ We are informed that good results and greater ease in use have been 

 obtained by mixing the nitrate of lime with ashes before sowing it. 



