360 
Chemical Composition and Commercial Value of 
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 combiuation with a trace ofi - o -o 
\ o lb J^ oo 
organic matter / 
Lime 40' 70 38-20 
Magnesia -34 1-34 
*Pliosphoric acid 28-32 24-24 
Oxide of iron ■> 4-87 4-81 
Alumina / .. .^-72 
t 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'.^2 
t Equal to carbonate of lime 11*04 l'2-20 
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 res])ecting 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 (juite recently been communicated by a Frenchman — 
a M. Roblique — in the 'Comptes Rendus.' This gentleman 
recommends us to mix pulverised phosphatic nodules with 
