MANUFACTURE OF SUPERPHOSPHATE 75 



is fitted with solid oak or pitch pine door consoli- 

 dated inside by planks placed crosswise in the 

 gutters. The chinks of the planks and the doors 

 are luted with a paste of clay so as to prevent air 

 penetrating. 



In the early days of manure manufacture only 

 one "house" was used, and the mixer was installed 

 in the center of the ceiling of the house; then two 

 houses were installed with the mixer stride-legs 

 between them; finally, later on, four houses have 

 been built and the mixer placed at the crossing of 

 the party walls. This plan gives excellent results. 

 The mixer in that case is fitted with four discharge 

 doors each of which empties into a house of its 

 own. Each "den" has a capacity of 50 to 100 

 tons according to the size of the factory. 



Attempts have been made to find methods of 

 rendering phosphate soluble more rapidly and more 

 completely than by the processes actually used. 

 To accomplish this the-phosphate is reduced to a 

 very fine state to pass through a No. 100 sieve. 

 A paste is made of it by drenching it with water 

 or with acid of 10 to 20 degrees Be. and finally 

 adding the rest of the acid at 60 degrees Be. But 

 this process was soon abandoned, for the action 

 was too violent and the metal of the mixer was at- 

 tacked by the acid. 



Attempts have been made to render phosphate 

 soluble by mixtures of hydrochloric and sulphuric 

 acid without any great advantage. The super- 

 phosphate contained 30 per cent of hydrochloric 



