22 



BULLETIN 144, U. S. DEPARTMENT OF AGRICULTURE. 



It is not stated whether the acid phosphate was made by the "open- 

 dump" or "den" method, but an inspection of the table will show 

 that little change has taken place in the material after keeping several 

 months. In Table VI are given the analyses of two piles of acid 

 phosphate sampled after standing certain definite periods of time. 

 The acid phosphate in both cases was made by the "open-dump" 

 system. 



Table VI.- — Analyses of acid phosphate from two piles after standing for certain periods. 



Time of storage. 



Available 

 phos- 

 phoric 

 acid. 



Insoluble 

 phos- 

 phoric 

 acid. 



Moisture. 



No. 1: 



Per cent. 

 15.70 

 16.63 

 16.93 



15.55 

 15.70 

 17.19 



Per cent. 

 2.05 

 1.02 



.47 



1.50 



1.S0 



.18 



Per cent. 

 12.80 





12.70 





13.80 



No. 2: 





3 davs 



12.60 





13.94 







Although the percentage of available phosphoric acid continued to 

 increase after storing the material for several months, this increased 

 availability was largely offset by a corresponding rise in the moisture 

 content of the product. 



DISINTEGRATING THE ACID PHOSPHATE. 



Before acid phosphate can be bagged and shipped it must be broken 

 up and put through coarse sieves. In the case of superphosphate 

 which has been carefully made it often suffices to throw the material 

 by means of shovels upon inclined screens, the force of the impact 

 being great enough to disintegrate the lumps. When dealing with 

 acid phosphate, however, which has been improperly made or stored 

 for a long time, it is often necessary to use a machine for breaking up 

 the material. The ordinary crushing devices do not answer for this 

 purpose, owing to the tendency of the acid phosphate to pack or be- 

 come sticky when pressure is applied, so disintegrators of a special 

 type must be employed. 



In a machine like that shown in Plate V, figures 1 and 2, complete 

 pulverization is brought about by submitting the material to innu- 

 merable shocks, but in such manner that no opportunity is given the 

 acid phosphate to pack or gum together. 



The disintegrator consists of a number of concentric cages made up 

 of steel bars, all of which are inclosed in a casing. The cages are 

 usually four in number, the first and third attached to a shaft which 

 revolves in one direction and the second and fourth attached to 



