ELISHA MITCHELL SCIENTIFIC SOCIETY. 27 



PHOSPHORIC ACID INSOLUBLE IX WATER. 



At mixing 4. 04 per cent., at end of first week 2.50 per cent., 

 a loss of 1.54 per cent. The greatest loss was at the end of the 

 ninth week — 1.82 per cent., corresponding to the gain in soluble 



phosphoric acid. 



REVERTED PHOSPHORIC ACID. 



At mixing 1.58 per cent., at end of first week 1.58 per cent. 

 The greatest difference was at the end of the fifth week, when it 

 had fallen to 1.2J per cent., a loss of 0.37 per cent. At the end 

 of the ninth week there was a gain of 0.20 per cent. 



"insoluble" phosphoric acid. 



At mixing 2.45 per cent., at end of first week 0.92 per cent., 

 and at end of tenth week there was none. 



It is unnecessary to proceed further in this way: the figures 

 stand for themselves. 



The chief point of interest is that the changes taking place in 

 acid phosphates, whereby more or less insoluble reverted phos- 

 phates are produced, are due mainly to the high temperature in 

 the heaps. This temperature may at times he as high as 240' 

 F., and appears to induce the formation of iron-calcium phos- 

 phates, or, if aluminum he present, of iron-aluminum-calcium 

 phosphate-, li' some method could he devised by which a rapid 

 cooling of the freshly made acid phosphate could lie attained, we 

 would hear less of reversion. This is more particularly the 

 case when mineral phosphates containing considerable quantities 

 of iron and aluminum are w>v(\ for the manufacture of acid 

 phosphates. 



With the present condition of the fertilizer trade, however, 

 the product must he made in large quantities and stored in ware- 

 houses, where it often reaches a higher temperature than in the 

 mixer. In the warehouse the stuff dries itself, becomes light 

 and porous, ami i- easily disintegrated, which i- uol the case if 

 it he rapidly cooled a- it <'<>ni«-- from the mixer. ( )n the whole, 



