PETER SPENCE 271 



using this phosphate as a fertiliser; or, pure 

 ammonia was added to the monophosphate, 

 and a tri-ammonic phosphate suitable for use 

 in sugar refining was formed. 



The process of the fourth patent consisted 

 in mixing the mineral phosphate with sulphate 

 of soda (salt cake) coal and a little oxide of 

 iron, and heating these together until decom- 

 position took place; then lixiviating out the 

 phosphate of soda that is formed; to this 

 solution caustic lime is added, phosphate of 

 lime is precipitated, and caustic soda remains 

 in the liquor, this is boiled down in the usual 

 way; the precipitated phosphate is either used 

 as it is or is converted into superphosphate. 



By the fifth patent he evaporated the 

 sulphuric acid solution of the Redonda to a 

 specific gravity of 1*5, added sufficient sul- 

 phate of ammonia to convert all the alumina 

 into alum, and finally a certain proportion of 

 sawdust as absorbent. The whole, congealed 

 into a dry granular mass, formed a highly 

 phosphatic and nitrogenous manure. 



Spence was so confident of the success of 

 his Redonda alum process that he decided to 

 erect plant on a large scale, and to alter the 

 arrangement of his works. He was too 

 sanguine, and his conclusions were at least 



