90 
PREPARATION OF CALOMEL. 
come almost universal, in France, of employing this finely- 
divided calomel. It must be admitted, nevertheless, that in 
whiteness and fineness of division, the calomel prepared in 
France would not bear comparison with that imported from 
England. 
In order to improve the product, and render the ope- 
ration more easy, I proposed to substitute a current of air 
instead of steam, to effect the minute division of the calo- 
mel. 
The apparatus consisted of an earthen tube placed across 
a furnace, in which the calomel in small lumps is heated. 
A current of air is passed continually through the tube by 
means of a centrifugal blowing-apparatus, so as to carry the 
vapour as it is formed into a receiver. If no obstacle be 
offered to the current, the calomel is in so fine a state of 
division, that it would be carried to a great distance; to 
obviate this, I found the best plan was, to make the tube 
terminate in a chamber divided into three stories by shelves 
running nearly across, and the communication from one to 
the other being at opposite sides of the chamber. The 
calomel was made to enter at the bottom of the chamber, 
while a pipe from the top, terminating in a vessel contain- 
ing water, allowed the air to escape. This plan answered 
very well. 
Numerous experiments, however, have induced me to 
relinquish this process in favor of another more simple, and 
in every respect satisfactory. 
I now employ neither steam nor a current of air: my ap- 
paratus is composed simply of a tube and a receiver; and I 
obtain the calomel, in the finest state of division and of beau- 
tiful appearance, by a single operation. The principle of 
this operation is similar to that of the process for the manu- 
facture of flowers of sulphur. 
The vessels in which I heat the calomel are earthen tubes, 
about four inches in diameter and eighteen inches long. 
These are closed at one end and open at the other, and each 
