62 
UNGUENTUM HYDR ARGYRI NITRATIS. 
United States, this view of the subject pronounced to he a 
"mistake that it is " the olive oil which is hardened by the 
supernitrate of mercury, and that the ointment is firmer when 
made with that oil alone, than with a portion of lard." Hence 
in the last edition of their Pharmacopoeia, they have directed 
neat's-foot oil to be substituted for that of olive, with, it is 
stated, decided advantage, thus, — " Take of purified mercury, 
1 oz., nitric acid, 11 fluid drachms, fresh neat's-foot oil, 9ozs., 
lard, 3ozs.; dissolve the mercury in the acid, then melt the 
oil and lard together, and when they begin to stiffen (upon 
cooling) add the solution and mix them." It is admitted, 
however, that change had taken place in some which had been 
prepared upwards of four months, which, although soft, had 
partially assumed a greenish color. The acid is stated to have 
been of specific gravity 1.325. 
Amid these contradictory statements, T made a few experi- 
ments a few years since, which I think afford a practical solu- 
tion of the difficulty: Under the idea that the hardening of 
the ointment was due to the olive oil, I prepared some by the 
substitution of oil of almonds, and obtained an ointment of 
beautiful color and consistence, and which was not altered by 
keeping. The next trial was not equally successful; from 
which it was evident that the result depended more on the 
manipulation, and perhaps on the acid, than on the particular 
kind of fat employed. Since that time I have never had my 
ointment become hard, or materially changed by fkeeping. 
On a comparison of various experiments, I am satisfied that 
the point most important to be attended to, is the due regula- 
tion of the heat, so as to effect the needful decomposition of 
the nitrate. If the mixture be made at a low temperature, no 
effervescence takes place, and the ointment so produced will 
become hard in a few days, of a greenish white color, and 
eventually of a consistence that may almost be powdered; but 
if the oil or fat is heated to a sufficient temperature, or the 
quantity operated upon is large enough to generate the heat re- 
quired, strong effervescence takes place, much gas is evolved, 
and a perfect article is produced, of a fine golden color and 
the consistence of butter. 
