STORING OF SUPERPHOSPHATE. 



137 



TABLE XLIII. — SHOWING CHANGES IN COMPOSITION WHICH 

 TENNESSEE SUPERPHOSPHATES UNDERGO IN FOUR AND A 

 HALF MONTHS FROM DATE OF MAKING. 



Mixings made 

 2 September, 189S. 



PoO. insoluble 



Soluble Al.,0, + FeoO- 



Insoluble ALO, + Fe^O. 



Free Acid 



a 



h 



c 



a 



b 



c 



a 



b 



c 



a 



b 



c 



2-27 

 2-20 



1-98 

 0-90 

 1-07 



1-28 



+ 0-2G 

 + 0-27 

 + 0-29 



U _ 

 5-50 

 5-o0 

 6-10 



+ 

 + 



l-Oo 

 1-01 



Sample of same 



Superphos- 

 phate Analysed 

 17 November, 



1898. 



2-35 



2-33 



2-32 

 0-65 + 0-17 

 0-87 + 0-18 

 1-09 + 0-22 



— + 1-21 



— + 1-20 



— + 1-17 

 4-20 

 4-30 

 4-80 



Paysan adds that not being able to find the cause of retrogradation 

 in the sesquioxides, he tried to find it elsewhere, and he quotes the 

 follo\Ying case of a delivery of Florida phosphate. The samples taken 

 the first day at four different points looked well ; the next day fresh 

 samples were taken, this time going further forward than the points 

 explored the day before, and it was found that in certain places the 

 phosphate was darker than in others, and contained much impurity. 

 Two samples of this kind, taken at two different points, gave the 



following figures 



Phosphate of lime 

 Sand 



a 



An average sample of the whole cargo gave the following 

 analysis. Phosphate of lime 77*73, oxide of iron and alumina 2-13 

 per cent. The pure phosphate behaved in a normal fashion. In 

 working it dissolves completely and gives no retrogradation, but 

 when wrought up with the impure part retrogradation was rapid, 

 1-52 to 2-14 per cent of insoluble was obtained against 0-75 with the 

 pure superphosphate. This example well explains contradictions 

 and obscure points. But Dr. Paysan does not admit the theory of 

 pressure in the question of retrogradation. He has often remarked 

 a tendency to retrograde in superphosphates as soon as they have 

 gone through Carr's disintegrator. He does not ascribe trans- 

 cendent merit to Dr. Lutjens' processes. He regards them as- 

 elegant and useful auxiliaries in superphosphate manufacture, but 



