ON EMPLASTRUM PLUMBI. 
175 
and treated in the manner directed for the formation of lead 
plaster. This parcel underwent the same change in colour, 
as noticed in the fourth experiment. Two and a quarter 
hours were required for its completion, and four and a half 
pints of water were consumed. The deposite of metallic 
lead in this instance was the same as that in the parcel 
where red lead was used. The plaster, however, after 
standing undisturbed for about five minutes, and thrown 
into cold water, had as fine a consistence as that made with 
English litharge. 
7th. Eight pounds of lard being melted, five pounds of 
litharge (American) finely powdered was stirred into it, 
and a small quantity of water being added, the boiling was 
commenced and continued briskly, with constant stirring, 
until the water was driven off 5 then the mass attained a 
temperature above that of boiling water; it was removed 
from the fire and a fresh supply of water being added, an 
immediate union of the fatty acids and oxide of lead took 
place ; a plaster being formed in a much shorter time than 
when the mode prescribed by the Pharmacopoeia is closely 
adhered to. This plaster was of a good consistence, and as 
white, and apparently as perfectly formed as that prepared 
in the ordinary way. The danger of discolouring I conceive 
to be but little if any greater by this mode of proceeding, 
than by that directed by the Pharmacopoeia; for the same 
reason that syrups may become empyreumatic by rapid 
boiling, the steam forming bubbles on the bottom of the 
vessel where the fire acts, as in this case the temperature 
would be about the same. 
8th. A quantity of lard was boiled with an equal weight 
of water for fifteen minutes, then removed from the fire, 
and the lard allowed to harden. The lard was then sub- 
jected to the action of litharge and formed a plaster in 
much less time than lard that had not been treated in this 
way. A portion of the plaster resulting from experiment 
