72 CHEMICAL MANURES. 



phosphates, superphosphates which answer all requirements since 

 it has been recognized that dryness and the pulverulent state of the 

 superphosphates depends in the first place not on their percentage 

 of moisture but on their free acid content. The recently discovered 

 phosphates of Christmas Island and Ocean Island likewise enable 

 phosphates with 20 to 21 per cent of phosphoric acid soluble in 

 water to be produced. Thus, as already observed, it is Florida 

 phosphate which has been the occasional cause of the methods of 

 working which we have just enumerated. This same phosphate 

 more than any other has put chemists to the test owing to its high 

 percentage of oxide of iron and alumina, which are the great 

 enemies of superphosphate manufacturers. The retrogradation of 

 the soluble phosphoric acid caused disagreeable surprises for the 

 chemist and manufacturer, and if the means of prevention be not 

 possessed by a factory working on the large scale, the causes and 

 conditions under which they are produced have been determined. 

 Chemistry, the inseparable companion of industry, has taken a con- 

 siderable part in the progress realized in superphosphate manufacture 

 from its birth to the present time. Chemists are attached to all 

 manure factories ; to them belongs the merit of freeing this industry 

 from empiricism so as to establish it on a truly scientific basis. French 

 chemisis have had a large part in the development of the manure 

 industry. Their learned researches joined to that of French geo; 

 logists have greatly contributed to the realization of the value of 

 the French phosphate deposits, the immense reserves of which will 

 suffice for a long time to cover the requirements of French 

 agriculture.^ 



^ That we in Great Britain have not a voluminous special literature dealing 

 with the chemistry of manure manufacture, in no way detracts from the merits 

 and claims of British agricultural and manure works chemists. Our Patent 

 Office records prove that they have been first in the field in all branches of 

 research in this domain. Both French and German current methods of pre- 

 cipitated phosphate manufacture, double superphosphate manufacture, and such 

 like, are all borrowed from British patents like those of Professor ^Yay,. 

 Benjamin, Tanner, etc., away back in the sixties and seventies. 



