62 MANUFACTURE OF FERTILIZING MATERIALS 



charged intermittently in 4 to 5 cwt. lots into a 

 mixer composed of a lead-lined wooden tank, pro- 

 vided with an agitator, where it is mixed with 

 chamber acid (vitriol of specific gravity 1.53 to 

 1.61, containing 62.53 to 69.43 per cent H 2 S0 4 ), 

 run in as required from an adjacent tank. The 

 quantity of acid needed varies with the composi- 

 tion of the phosphate, 13 to 18 cwts. per ton of 

 phosphate being the usual limits. The mixer is 

 built above a brick chamber known as the "pit' 7 

 or "den/ 7 and into this the semi-fluid mass, after 

 it has been agitated for a few minutes, is dis- 

 charged through a chute. The temperature of 

 the mass in the pit rapidly rises to 110 C. Much 

 gas is evolved (CCb, HC1, and HF), and solidifi- 

 cation sets in. The gases are drawn off through 

 flues, and pass through a scrubber, necessary on 

 account of the objectionable character of HC1, 

 and still more of HF. When the pit is nearly full, 

 one of the sides, which is of wood and removable, 

 is taken down and the product dug out and passed 

 through a disintegrator, whereby it is reduced to 

 powder. When mixed manures are being made, 

 potash salts and nitrogenous materials are mixed 

 during passage through the disintegrator. 



In mixing and making of fertilizers, it was first 

 proposed to make the ingredients correspond to 

 the analysis of the plant. This method was prac- 

 ticed for some time, biit it was found that there 

 was already in the soil more or less available plant 

 food and that fertilizing material was often applied 



