272 
ON LEAD PLASTER. 
Lemery, among others, explains the process in the 
Pharmacopee Universelle, as follows : — 
" If the quantity of the decoction prescribed does not 
suffice to finish the preparation of the plaster, more must be 
used ; but none must remain, for the moisture would pre- 
vent the plaster from being of good consistence, and conse- 
quently not adhesive : that is to say, not spreading well on 
leather or cloth. 
" If then the plaster still boils, although solid and cooked, 
it is a sign that some of the decoction yet remains ; this is 
to be evaporated, and then the plaster retained for half an 
hour at a gentle heat, continually stirring with a wooden 
spatula, so as to render it dry and more adhesive." 
I had not attended to this observation of Lemery, when 
accident led me to recognize its correctness. On preparing 
the simple plaster in the laboratory, it wanted but a few 
minutes of being finished, but the water was deficient, and 
the temperature rose, some portions were decomposed, com- 
municating a brown tinge to the mass, but not sufficient to 
prevent its employment. This plaster when spread on cloth 
possessed (whiteness apart) all the properties of an adhesive 
plaster, viz. suppleness, brilliant aspect, and above all, the 
advantage of keeping for a long time without contracting 
that strong odor which lead plaster obtains after some time. 
From that time I have gradually diminished the amount 
of water directed by the Codex, and after several trials have 
adopted the following formula : — 
Lard, olive oil, 5000 
Litharge, 5000 
Water, 1800 
This quantity of water added at the commencement, is 
always sufficient. The operation to be performed on afire 
of such activity as to keep up ebullition, without interrup- 
tion, for two or two and a half hours. The appearances are 
