70 MANUFACTURE OF FERTILIZING MATERIALS 



words, they wrought like masons making mortar. 

 But for thirty years this work has been done ex- 

 clusively by mechanical means, which enables the 

 work to be done more rapidly and in larger quan- 

 tities at a time. 



Consequently the mixing pit has been enlarged 

 so much that in its new form it constitutes the 

 chamber, or more familiarly the "den" or "house" 

 in which the phosphate is rendered soluble. This 

 chamber is closed and care has to be taken to elim- 

 inate and render inoffensive the toxic gases which 

 are disengaged from the material during its de- 

 composition. 



To mix the acid with the phosphate a "mixer" 

 or mixing machine is used, constructed and in- 

 stalled thus : The mixer consists of an egg-shaped 

 pan 64 inches wide at the top and 48 inches wide 

 at the bottom, fitted with two discharge doors, 

 with lever and counterpoise, which enables the 

 mixing to be run into an enclosed space, called the 

 decomposition chamber, which is built on the 

 ground floor or sunk in the ground. In the pan a 

 vertical shaft turns, driven by a cog-wheel gearing 

 and carrying blades of a special form arranged in 

 a helicoid manner; these lift, throw down, and trit- 

 urate the mass, after the style of a plough as it 

 works the ground, and prevent it at the same time 

 from being deposited and attached to the sides. 

 It suffices to pull the bent levers to open the dis- 

 charge doors, and thus let the liquid fall into the 

 decomposition chamber, "den" or "house." 



