176 



UNIT VALUES 



8 X 20 X 100 

 2240 x 15 T 75 = 



or its value "per unit" = - 



' = 



= 10'2s. = 10s. 2Ad. 



In sulphate of ammonia, containing, say, 24 '5 per cent of 

 " ammonia," equal to 20*2 per cent nitrogen, if its price be taken at 

 12 per ton, nitrogen costs 



= 0-53, per Ib. - 6-36d. pei- , 



12 x 20 



or its value "per unit" = . . = ll-83s. = 11s. lOd. 



20'2 



The two methods of expressing values are related to each other in 

 a simple manner. It is evident that the price "per unit," since it 

 refers to the price per ton for each per cent of the constituent in 

 question, is really the price of T ^ of a ton of the actual manurial 

 constituent. In other words, it is the price of 22-4 Ib. Obviously the 

 price per Ib. multiplied by 22-4 will give the equivalent price " per 

 unit ". 



In a similar way, the value of phosphorus pentoxide and potas- 

 sium can be calculated from the market prices of the various phos- 

 phatic and potash manures. As in the case of nitrogen, the values 

 obtained vary in the case of different manures. 



Tables are sometimes published giving the value of the three prin- 

 cipal manurial substances per unit in various commercial manures. 

 The following table, calculated from one given in the Transactions of 



