156 
MR. DAVY ON A SIMPLE ELECTRO-CHEMICAL METHOD 
the zinc applied, the mercury will presently be reduced to the metallic state, 
and the copper will be whitened. The results will be analogous, if similar 
experiments are made with solutions of corrosive sublimate in alcohol and 
ether, provided a little water be employed when the zinc is applied, or if pla- 
tina be substituted for the copper. 
The following is a beautiful and extremely delicate mode of reducing corro- 
sive sublimate, and of obtaining the mercury in a sensible form ; and it may 
of course be applied to other compounds of mercury. Put a drop or two of 
an aqueous solution of corrosive sublimate into a small platina crucible, add 
about an equal bulk of muriatic acid, and apply the zinc for a short time, 
when the mercury will be reduced ; part of it on the platina, which will appear 
of a brighter white colour, and part of it will amalgamate with the zinc, 
whitening it and making it brittle at the point of contact. Wash the crucible 
with pure water, dry, and cover it with a piece of plate glass, and heat it with 
a spirit lamp : the mercury will rise and be condensed as an extremely fine 
white powder without metallic lustre, and it may be easily collected from the 
glass by the finger, so as to be exhibited in minute globules, visible by a high 
magnifying power, even when a single drop only of the solution has been 
operated on. 
I repeated the preceding experiment in the platina gilt crucible. The instant 
the zinc was applied the surface of the gold was whitened. Afterwards the 
mercury was collected by sublimation on glass. 
The solution of corrosive sublimate may of course be readily reduced on 
platina when the zinc is applied without the addition of any acid, as in the in- 
genious mode proposed some time since by Mr. Sylvester, and afterwards sim- 
plified by Dr. Paris. I am disposed to prefer the use of platina to that of gold, 
not only on account of the great difference in their commercial value, but be- 
cause I found the surface of gold tarnished after the mercury had been sub- 
limed from it, which was not the case with the platina. I did not, indeed, 
ascertain if the gold I employed contained any alloy ; — it was supposed to be 
pure. 
A very simple mode of detecting corrosive sublimate, whether solid or dis- 
solved in water, alcohol or ether, which I have not seen any where noticed, is, 
to put on a bright surface of copper, a bit of the solid compound, or a drop of 
