120 
PHARMACEUTICAL PREPARATIONS. 
consistence could be made from the ingredients and propor- 
tions indicated in the United States Pharmacopoeia, a series 
of experiments were undertaken. As these number about 
thirty, it is unnecessary to give a detailed account of them; 
general results only will be stated. 
1st. The Pharmacopoeial formula, where the ointment is 
prepared by melting together the lard and neats-foot oil, and 
when they begin to stiffen on cooling, mixing in the solution 
of nitrate of mercury, &c, does not produce a fine prepara- 
tion ; its consistence is too soft ; its color is a dark brown, 
and the proper reaction between the fat and the acid does 
not take place. 
2d. Heat is necessary to induce this reaction, and conse- 
quently to the formation of a good ointment ; but if carried 
too high, the excessive oxidation of the fatty matter occurs 
at the expense of the acid of the mercurial salt, separating 
a portion of this as insoluble sub-nitrate. 
3d. A particular limit should therefore be observed in 
the temperature at the period of adding the mercurial solu- 
tion, and this temperature is 204° F. The following formula 
is suggested, viz : 
Take of Mercury an ounce (Troy,) 
Nitric Acid (sp. gr. 1.5) eleven fluid drachms, 
Fresh neat foot oil, nine fluid ounces, 
Lard three ounces. 
Dissolve the mercury in the acid, allow the solution to 
stand until all the nitrous fumes shall have escaped, and the 
solution becomes colorless, (this may be effected by the aid 
of heat, if it is wished to proceed with the preparation with- 
out delay.) The lard and oil are then melted together, and 
as soon as the temperature rises to 190° F., add the cold 
solution, and continue the heat till the temperature of 190° 
F. is again reached, remove the vessel from the water bath for 
fifteen minutes, taking care to prevent the temperature from 
rising above this point ; then heat again to 204°, and 
