ELISHA MITCHELL SCIENTIFIC SOCIETY, 



57 



exists in a more easily decomposable form than it does in any other 

 superphosphate with which I am acquainted. It is reverted in- 

 stantly on diluting the aqueous solution. The same is true, to a 

 limited extent, of similar articles made from Charleston Rock. 



In the superphosphate itself, the rapidity with which reversion 

 takes place is largely dependent upon the content of Iron and 

 Aluninum. In most cases, if all the phosphoric acid has been ren- 

 dered soluble, the reversion proceeds slowly. But if any unattacked 

 Iron and Aluminum oxides are present, the reversion proceeds rap- 

 idly. (Compare H. Joulie, Compt. Rendus 88, 1879, p. 1324, and 

 Carl Ferd. Meyer, Zeit. An. Chem. 1880, p. 309.) 



I have recorded in the following tables the results of some observa- 

 tions made on Superphosphates prepared from Red Navassa Rock. 

 The material used was of uniform fineness, the whole of it passing 

 through a 60 mesh sieve. The samples were prepared so that in one 

 there should be about 5 per cent. , in another about 8 per cent. , and 

 in the third about 14 per cent, soluble phosphoric acid. 



The same method of analysis was used in every case. All the 

 phos. acid determinations were made with Ammon. Molyb. For 

 the estimation of insol phos, acid there was used a slightly alka- 

 line solution of Ammon. Citrate, 100 c. c. to 2. Gms. time 30 mins. 

 Some of the comparative determinations of insol. phos. acid had 

 to be omitted from lack of time, but it is hoped that those that ap- 

 pear will prove to be sufficient for the end in view. The reverted 

 phos. acid was determined by difference. 



TABLE I. 



8 



