upon oxygenized and hyper oxygenized muriatic Acid t &c. 159 
of mercury for every is pounds of corrosive sublimate. But, 
from the above experiments, it would appear, that a smaller 
quantity of mercury might strictly answer. However, from 
the results of minute investigation, we should not conclude 
too hastily upon preparations on the great scale; and, I rather 
think, that the excess of mercury ordered by the Pharmacopoeia 
is a useful precaution. 
In my experiments, I attempted to reduce, by means of 
copper, iron, or zinc, the mercury contained in the mercurial 
salts. Iron did not answer the purpose : zinc precipitated the 
mercury a little better ; and copper produced a change which I 
did not expect. If a bit of copper be put into a solution of cor- 
rosive sublimate, a white powder shortly falls to the bottom; 
and that powder is calomel. When washed, it does not contain, 
an atom of copper, nor of corrosive sublimate. 
Before I conclude these considerations, I must say, that 
whether calomel be prepared in the dry or in the humid way,* 
it does not seem to differ chemically ; nor does it contain any 
* By the humid way, I do not mean precisely the method of Scheele. That che- 
mist desires us to boil the acid with the mercury, after they have ceased to act upon 
each other at a low temperature. By this method, the nitric acid takes up an excess of 
mercurial oxide ; and the nitrate of mercury thus formed, precipitates by water. 
Therefore, when this nitrate of mercury is poured into the dilute solution of muriate 
of soda, according to the formula of Scheele, the.action, on the part of the solution, 
is twofold',. 
1st. The water acts upon one part, and precipitates an oxide, or rather an insoluble, 
subnitrate of mercury. And, 
2dly. A double decomposition takes place between the nitrate of mercury and the 
muriate of soda. It is with reason, that the medical world have supposed the calomel 
of Scheele to be different from that prepared in the humid way ; for it is, in fact, 
calomel, plus an insoluble subnitrate of mercury. In the first part of Scheele’s 
