me 
on Phosphoric Acid. 7 
Experience soon taught me that there were 
various superphosphates of lime, or such that 
differed much from each other in the propor- 
tions of acid. This does not however appear 
very strikingly from any variation in the 
quantities of the products obtained by using 
more or less sulphuric acid. I expected that 
by using more sulphuric acid I should obtaina 
higher superphosphate ; but 1 could not per- 
ceive much difference in the quantity of inso- 
luble residue when much less sulphuric acid 
was used; only in this case a great part of 
the phosphate of lime remained undecom- 
posed. 
Though I have not vet. perfectly satisfied 
myself as to the. requisite proportions, I be- 
lieve that 10 parts of calcined bones require 
} parts by weight of concentrated sulphuric 
acid, to produce the most complete and ‘per- 
fect decomposition.* ‘The acid may be diluted 
with 6 times its weight of’ water; the bones 
should be finely pulverized, and the mixture 
* It was not till the present year (1817), that I met.with 
an essay of the ingenious Pelletier in the Journal de Phy- 
sique for 1785 on the manufacture of Phosphorus, in which 
he prescribes as the result of experience, 15 Ibs. sulphu- 
ric acid to 18 Ibs. of calcined bones (that is, 8: to 10). 
See Vou, 7, page 28. 
