MINUTE DIVISION OF MERCURY. 249 
Two drachms of peroxide of mercury were triturated with 
one drachm of the metal. For a considerable time very little 
effect was produced, excepting that the powder assumed a 
black color, the metal remaining in a fluid state : on adding a 
little water, the mercury gradually disappeared, and the mix- 
ture ultimately became a reddish black powder. This was 
placed on a filter and dried in the dark. When dry a globule 
of mercury was separated ; the remaining powder was of a 
greenish red color. This show's that the peroxide of mer- 
cury, when moist, has the power of dividing the metal with- 
out imparting to it the oxygen required for converting it into 
a protoxide. 
Hyd. cum creta, when used as plate powder, gives silver a 
peculiar black tinge and brilliant polish, dependent on the 
amalgam formed by the two metals. A mixture of the cine- 
reous oxide of mercury with chalk has a very different effect^ 
which may be easily observed by cleaning a silver spoon with 
each of the two powders and comparing them together. It is 
clear that mercury, when in the state of an oxide, does not 
possess the same power of uniting with silver as an amalgam. 
Extractum rhei, which was rather hard and tenacious, was 
triturated with hydrarg. cum eret$ : globules were separated 
as usual. A few drops of water were added, and by continu- 
ing the process, the mercury was again absorbed ; the mass 
was then too soft for dividing into pills. The division of 
mercury by extract is probably analogous to the division of 
oil and wax by water in cold cream. If stale cold cream be 
stirred in a mortar, a large proportion of the water separates, 
but the union is restored by persevering in the trituration. 
M. Desmarest, in an article in the Journal de Pharmacie 
on the division of mercury (1829,) informs us, that "fat and 
viscous substances have not the property of invariably main- 
taining the division of mercury : but they lose it when their 
consistence is increased to that point at which they may be 
considered more like solids than liquids, because then the 
envelope which they form round the globules, having lost its 
flexibility, breaks, and allows them to re-unite. Having 
