Phosphates 



Dissolved Bones. — It was Liebig who suggested 

 treating bones with sulphuric acid, and Lawes who 

 utilised the suggestion at Deptford in 1842-1845 

 in the manufacture of his superphosphate ; but 

 being too dear, those superphosphates were 

 abandoned in favour of the cheaper mineral phos- 

 phates. They were called Bone Superphosphates, 

 and contained about two-thirds phosphoric acid 

 soluble in water, while the remaining third, being 

 parti}' dicalcic phosphate, was also sufficiently 

 assimilable. Bones, bone ash, and spoilt char were 

 utilised in their manufacture, and being expensive, 

 the manure was, in time, much adulterated. This 

 bone super has been advantageously and economi- 

 cally replaced by ordinary super. A more or less 

 diverse series of dissolved bone compounds was 

 derived from it, but they are not interesting. 



Bone Ash. — This is chiefly used to make Bone 

 Superphosphate and comes from abroad. It is 

 rich in phosphate, sometimes containing 80 per cent., 

 and gives a good superphosphate, but is still too 

 dear. The unit of phosphate in bone super ought 

 not to cost more than in ordinary super, that of 

 phosphate in ordinary bones more than finely 

 ground mineral phosphates, or that of steamed bone 

 flour more than reverted super. Generally speak- 

 ing, bone super costs too much and therefore cannot 

 be recommended. 



Animal Charcoal. — For a long time animal char- 

 coal has occupied an important position in the range 

 of manures coming from bones. To make it, the 

 bones are cleaned and then burnt in a closed 

 receptacle. During the calcination part of the 



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