260, 261] Valuation of Manures by Analysts 153 



by using it. Thus, it is by no means proved — in fact, it is 

 highly improbable — that the soluble phosphate in dissolved 

 bones is any more efficient as a manure than that contained in 

 a mineral superphosphate. Therefore, so far as the produce of 

 this manurial constituent is concerned, it is of the same value 

 in each case ; whereas commercially the price of the soluble 

 phosphate in bones is very much higher than that in mineral 

 superphosphate. 



260. Definition of a Unit. — The commercial unit of any 

 manurial constituent is the hundredth part of a ton. Thus, if 

 a mineral superphosphate be found to contain 27*85 per cent 

 of soluble phosphate, it is said to contain 27*85 units of soluble 

 phosphate per ton. 



N.B. — The commercial unit of soluble phosphate is really 

 the unit of Ca 3 P 2 8 equivalent to the soluble phosphate ; thus 

 it is sometimes quoted as ' phosphate made soluble.' 



261. Valuation by Units. — Of course the prices of 

 various manures fluctuate considerably, and it is therefore 

 necessary, when an exact valuation is required, to know the 

 present prices per unit. These are published every month by 

 some of the principal manure merchants, and also by several 

 of the leading agricultural societies. The following table shows 

 the form in which these prices are published, and gives an idea 

 of what those prices are per unit : 



Phosphate made soluble (Ca 3 P 2 8 ) : s. d. s. d. 



From raw bones 2 8 to 2 10 



From bone ash . . . . . 2 8 ,, 2 n 



From mineral . . . . . . 2 2 ,, 2 5 



Insoluble phosphate (Ca 3 P 2 8 ) : 

 it 

 In natural guano 2 o ,, 2 4 



In bones or fish manures . . . . 1 3 ,, 1 8 



In ground minerals . . . . 1 o ,, 1 3 



In basic slag ...... o io| ,, 1 1 



In mineral superphosphate . . . o 6 „ o 8 



