of British and Foreign Salt. 103 
these varieties contain, is decomposed at a red heat, and 
deprived of its acid. 
The following table shews the quantity of water contained 
in several kinds of salt, inferred from the loss which they 
sustain by ignition during equal times, after being first dried 
at 212 0 . 
100 parts of large grained fishery salt contain of water 3 
100 - foreign bay salt (St. Martin's) - -3 
100 - - do. - ( Gieron) - - 
100 - - - do. Cheshire common salt - if 
100 - do. - stoved salt - - 
The loudness and violence of the decrepitation was, as 
nearly as could be judged, in the same order, and was most 
remarkable in the large grained varieties. 
To determine the proportions of real muriate of soda in 
those varieties of artificial salt which are nearly free from 
earthy muriates, I employed also the process of decomposition 
by nitrate of silver. The following are the quantities of fused 
luna cornea, obtained from 100 grains of each of three vari- 
eties dried, previously to solution, at the temperature of 21 2 0 
Fahrenheit. 
100 gr. pure transparent rock salt gave of luna cornea 242 
100 stoved salt, remarkably pure - - 239 
100 fishery salt. do. - 237* 
* From 100 grains of pure artificial muriate of soda, previously heated to redness. 
Dr. Marcet has since informed me, that he obtained 24.16 grains of fused luna 
cornea. The weights of the precipitates thrown down in my experiments by nitrate of 
silver, are not, I am aware, exactly those which might have been expected from the 
table of the comparative proportions of water given in the text. Each experiment, 
however, was twice repeated with every precaution I could adopt, and with the same 
results. That different kinds of salt give different proportions of luna cornea, is 
