240 
MINUTE DIVISION OF MERCURY. 
triturated with any substance that aids the division of its glo- 
bules, and extends their surface, appears to be susceptible of 
oxidation from the action of atmospheric air ; and the gray 
oxide formed by this operation is the basis of the common 
mercurial pill," &c. 
Pil. Hydrarg. " The trituration of the quicksilver in this 
preparation was formerly supposed to reduce it merely to a 
state of extreme mechanical division. But there is every rea- 
son to believe, that an oxidation of the metal is effected, and 
that the medicinal efficacy of the preparation depends on this 
oxide. Quicksilver, in its metallic state, being inert with re- 
gard to the living system, the activity of the preparation itself 
is a presumption of this; but it is further known that by agi- 
tation with atmospheric air quicksilver affords a portion of 
gray powder, soluble in muriatic acid, and which, therefore, 
must be an oxide, metallic quicksilver being insoluble in that 
acid." 
Mr. Murray having informed us that mercury is also in a 
state of oxide in the unguentum hydrargyri, proceeds, 
"There are even additional grounds for admitting this con- 
clusion, with regard to mercurial ointment. Unctuous matter 
appears in general to promote the oxidation of metals by the 
action of the air, as is exemplified in the green crust which 
copper speedily acquires when coated thinly with grease." 
# * * * * * '' r'Vf lU * A 
" The improvement of the ointment from keeping affords a 
similar presumptive proof. 
" Unctuous matter, more especially that of an animal 
origin, becomes rancid from the action of air, and this rancidi- 
ty appears to be connected with the formation of an acid pro- 
duced from fat — the sebacic. This change may take place, to 
a certain extent, during the trituration, and still more when 
the ointment is kept, and may promote the oxidation of the 
mercury, while any acid that is formed may combine with 
the oxide. According to this view, mercurial ointment will 
consist of unctuous matter, in which is diffused oxide and 
