PROPERTIES OF MANURES 233 



It is a valuable manure in more ways tkan one ; 

 but it must not be mixed with sulphate of 

 ammonia. It is of great value on moor and 

 peaty soils — especially in the fen districts of this 

 country. 



Superphosphates. — Bones, guanos and mine- 

 ral phosphates when treated with sulphuric acid 

 form the superphosphates of lime. It was in the 

 year 1840 that Liebig produced excellent results by 

 rendering the phosphate of bones soluble in water 

 by treatment with schwefelsaure or sulphuric acid ; 

 and the same process was applied by Sir John B. 

 Lawes (in 1842) to mineral phosphates with 

 enormous success. This is really the birth of the 

 superphosphate industry — an industry producing 

 millions of tons every year. 



Bone and guano superphosphates are of greater 

 value than those derived from mineral phosphates. 

 The object gained in using superphosphates is that 

 the tree is supplied with phosphoric acid in a 

 soluble (available) form for root-absorption — that 

 is, for the immediate use of the tree, shrub or plant, 

 whereas in the case of bones and other phosphates 

 that have not been vitriolised, time is required for 

 their decomposition in the soU. 



The following analyses represent good super- 

 phosphates : 



