376 Mr. Chenevix’s Observations and Experiments 
the mode of preparing calomel, is a striking example of such 
salutary corrections being successfully introduced. 
A few observations upon the formula according to which Dr. 
James's Powder, or the Pulvis Antimonialis, is prepared, and 
upon some properties of antimony, will place this assertion in a 
more prominent point of view. 
In order to prepare this powder, we are told to take equal 
weights of bone or hartshorn shavings and crude antimony, 
and calcine them together, at a high temperature : in other 
words, to take phosphate of lime, which already contains a great 
excess of lime, and add to it an oxide of antimony. In this pro- 
cess, it has been supposed, that the phosphoric acid of the bone 
or hartshorn will saturate, not only the lime with which it was 
originally combined, but, in addition to it, a new portion of me- 
tallic oxide, and a new portion of lime. For, what little sul- 
phuric acid might, during the process, have been formed by 
the combustion of the sulphur of the crude antimony, is dissi- 
pated, at a much lower temperature than that to which the 
powder is exposed. 
Every oxide of antimony with which we are acquainted, is 
volatile at a high degree of heat : it would therefore be hazard- 
ous to assert, that it is possible to preserve always the same 
proportion of antimony, whatever care may be employed in di- 
recting the operation ; and, a dissimilarity in the chemical result, 
must necessarily be attended with uncertainty in the medical 
application. 
To this property may be added another, no less conducive to 
error. That portion of oxide of antimony which is not volati- 
lized, becomes, in a great measure, insoluble in all the acids. 
What the effect of the gastric juice may be, upon a substance 
