Phosphatic Materials used for Agricultural Purposes. 13 



In good samples of Suffolk coprolites the amount of insoluble 

 siliceous matter varies from 10 to 14 per cent. ; No. 5, there- 

 fore, appears to be a very inferior specimen. 



Besides fluoride of calcium, they contain a good deal of oxide 

 of iron and alumina, which partially, at least, are thrown down 

 with the phosphates when the latter are determined by precipita- 

 tion with ammonia, as is usual in commercial analyses. In this 

 case the amount of phosphates will be stated in excess. The 

 true value of these pseudo-coprolites, therefore, can only be 

 correctly estimated if the phosphoric acid which they contain is 

 accurately determined. This has been done in the subjoined 

 analyses, which at the same time represent their detailed com- 

 position. 



Detailed Composition of Suffolk Coprolites. 



No. 1. No. 2. 



Moisture and water of combination with a trace of j K ~ 



organic matter } 5 ' 76 



Lime 40*70 38*20 



Magnesia -34 1*34 



* Phosphoric acid 28*32 24*24 



Oxide of iron \ 4-87 4-81 



Alumina / .. 3*72 



f Carbonic acid 5*08 5*37 



Sulphuric acid -87 1*40 



Potash -78 -56 



Soda -25 1-18 



Chlorine traces '07 



Fluorine and loss 3*02 4*31 



Insoluble siliceous matter 10*01 12*27 



100-00 100*00 



* Equal to tribasic phosphate of lime (bone-earth) 61-30 52 '52 

 t Equal to carbonate of lime 11*64. 12'20 



No. 1, it will be seen, is a very superior sample ; No. 2 repre- 

 sents a good average sample of Suffolk coprolites. In two other 

 samples, in which the amount of insoluble matter and phosphoric 

 acid alone was determined, I find : 



No. 1. No. 2. 



Insoluble siliceous matter 12'56 11*05 



Phosphoric acid 23*48 24*26 



Corresponding to bone-earth .. .. 50*87 52*56 



The remarks already made respecting the conversion of chalk 

 coprolites into superphosphate apply, with equal force, to the 

 pseudo-coprolites of the Suffolk crag. 



A new process for converting phosphatic nodules into effective 

 manures has quite recently been communicated by a Frenchman 

 a M. Roblique in the ' Comptes Rendus.' This gentleman 

 recommends us to mix pulverised phosphatic nodules with 



