[193 



PART VI 



ANALYSIS AND VALUATION OF 

 MANURES 



193. In commerce certain constituents of the substances 

 dealt with are valuable ; others are of no value. Hence 'a 

 commercial analysis — i.e., one which shall indicate the value of 

 a substance — will only estimate the valuable parts. Take, for 

 instance, the analysis of a superphosphate. Supposing that we 

 wished to make a complete investigation of the substances 

 contained therein, we should estimate the amounts of lime, 

 alumina, oxide of iron, sulphuric acid, phosphoric acid, and the 

 different alkalis, both in the soluble and insoluble state ; also 

 the amounts of moisture, organic matter, and siliceous matter 

 which it contains. In scientific investigations this is, of course, 

 often necessary. The agriculturist, however, who simply wishes 

 to know whether he has got value for his money or not, or 

 the manufacturer who wishes to value his manure, does not 

 want any such complex knowledge. In many cases nothing 

 is required but the percentage of soluble phosphoric acid, 1 

 and even when a so-called ' full ' analysis is asked for the 

 only constituents needed are those which are tabulated on 

 page 143. 



The methods described in this chapter are strictly com- 

 mercial ones, and will enable a student who has not time to go 



1 See notes on valuation, paragraphs 259-262. 



