MINUTE DIVISION OP MERCURY. 
253 
sugar, essential oil, gam, starch, faecula, and resin, it was found 
that the compound had the power of dividing mercury with 
great facility ; and the absence of coloring matter afforded the 
opportunity of observing its composition. A portion of it, 
rubbed on a plate of glass, showed no globules ; the color be- 
came darker, and the friction appeared to confirm the extinc- 
tion of the metal. But as it dried, very minute globules 
started up, as if suddenly liberated from confinement, in the 
same way as the metal makes its appearance on the filter, in 
the experiments with hydrarg. cum creta, &c. Resin, moist- 
ened with essential oil, was found to divide the metal with 
greater facility than any of the substances or compounds above 
mentioned. In two minutes the globules were invisible in 
the mortar to the naked eye. The other elements of an ex- 
tract, unassisted by resin and essential oil, were found to have 
much less power of dividing mercury, above half an hour 
being required for the extinction of globules. From what 
has been stated, we may conclude that 
The preparations under consideration are dependent for 
their efficacy on the impalpably minute division of the mer- 
cury, and if any oxide exist in them, the circumstance is ac- 
cidental, and the quantity so small as to be unimportant. 
Mercury, when alloyed with other metals, is speedily re- 
duced to a black powder, as stated by Professor Brande, but 
it is not yet proved that this powder consists entirely of 
oxide. 
Chalk has a very limited power of dividing the metal, or 
retaining it in a state of division. The vehicles for hydrarg. 
cum creta should, therefore, be such as are not likely to effect 
the separation ; and soft friable extracts possess the requisite 
texture. 
Extracts in general have great facility in dividing the par- 
ticles of mercury, and the direct union of the metal with some 
of these preparations might be attended with advantage. 
Extracts which are of a viscous, tenacious texture effect the 
division more speedily than those which are soft and friable ; 
