344 



VALUATION AND PURCHASE 



[chap. 



deducted from ;^4, 7s. 6d. leaves ;^3, lis. 3d. for the 

 phosphate. Dividing this figure by 59 (the percentage 

 of phosphate), we get is. 2|d. as the price of the unit of 

 phosphate of lime. 



Calculating in this way, the following figures are 

 obtained for phosphatic manures containing some 

 nitrogen : — 



We have thus obtained a valuation for tri-calcium 

 phosphate ranging from 2s. per unit for its water 

 soluble form in superphosphate, down to is, 3d. or less 

 per unit in bones or phosphatic guanos. 



Potassic fertilisers do not show a large variation, the 

 more concentrated and purified forms being naturally 

 somewhat the more costly, as follows : — 



Table XCIX.— Price of Unit of Potash. 



In dealing with mixed fertilisers the nitrogen is 

 generally the more important element to consider, as 

 being the most valuable and the most subject to 



