262 
Steel 
strains of pure charcoal, the diamond furnishing but 1 00 
grains of the same gas, from 28*825 grains of diamond. 
Also, that at the same temperature, 100 cubic inches 
of carbonic acid gas, weighs 47*26 grains, and 100 cubic 
inches of pure air or oxygen gas, weighs 33*82 grains. 
By my own repeated experiments I find that good lime 
stone, such as white marble, may be considered as com 
taining 43 per cent, of carbonic acid gas in a concrete state 
(that is uncombined with the quantity of caloric or heat 
necessary to render it gaseous or bring it to the state of 
air.) Hence every 100 parts by weight of good limestone, 
contains upwards of 12 parts by weight of pure carbon or 
charcoal, a consideration not commonly or sufficiently no- 
ticed. But owing to the size of the lumps in a charge at 
an iron furnace, and allowing for impurities, I do not think 
that 100 even of good limestone will yield in the usual jj 
heat of the furnace more than from 35 to 38 of carbonic 
acid gas, containing about 11 percent, of pure charcoal. 
I would further observe, that where the slag is an uniform 
dense glass, without blebs, all the limestone is deprived 1 
of its carbonic acid, for though oxygen or the base of I 
pure air, will unite to glass, carbonic acid will not . Pure 
limestone precipitated from a solution in acids by a solu- 
tion of pearl-ash, contains nearly 44 grains of carbonic 
acid in the hundred.* 
From the same experiments of Messrs. Allen and 
Pepys it appears, that 100 grains of carbonic acid gas 
* To try your limestone : Take 100 grains in powder, dissolve 
it in a mixture of 1-2 spirit of salt and 1-2 water. Wash with a 
pint of hot water what remains undissolved, and dry it for an hour 
in the heat of boiling water. Weigh it, and it gives the weight 
of the impurities. This method may be checked, by throwing 
clown the limestone by means of a solution of pearl ash, wash and 
dry it : weigh it : the weight added to the impurities ought to 
make up 100 grains. 
