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SELECTED ARTICLES. 
by a chemical process, is prepared with quantities of fatty- 
substances and litharge, which are not in accordance with the 
proportions proposed for the formation of a definite salt, and 
theory suggests that a certain quantity of the fatty substances 
is not acidified, but exists in the state of simple mixture. 
Nevertheless, the want of success always attending the at- 
tempts I have made to mix fatty substances with the plaster 
obtained by double decomposition, even in small quantities, 
has induced me to think, that this excess of fat does no remain 
free, but enters into some state of combination, whether, during 
the operation, there may be formed at the same time a neutral 
salt and an acid salt, which theoretically cannot be explained; 
or whether the salt of lead may be accompanied with an oleo- 
stearate of glycerine, which has been studied by MM. Pelouze, 
and Liebig. However this may be, as I think that the simple 
plaster has not, of itself, well marked medical properties and 
that it rather affords a vehicle for the application of substances 
which it is the practice to associate with it, and that the end 
Avhich I have proposed, is to procure a compound, the phy- 
sical characters of which will be absolutely similar to those 
of the plaster obtained by the ordinary method; I endeavoured 
in the first instance, to obtain the same consistence, by incor- 
porating with my plaster different quantities of fatty 
substances, but as I have stated before with unsuccessful 
results. Even olive oil, in very small quantity, afforded me 
a product entirely devoid of pliancy, and becoming strongly 
coloured by the light. Besides the same defect, lard comm.u- 
nicated to the plaster a degree of rancidity. I then employed 
fatty acids, which mixed perfectly well. The plaster, which 
contained one-eighth of its weight of them, lost none of the 
properties which it possessed, and acquired a consistence 
entirely similar to that of the plaster obtained by the direct 
action of litharge upon fatty substances. 
I think, then, that by the method which I have proposed, 
a product will be obtained as cheaply, of greater beauty, and 
more easily preserved; and, moreover, considerable economy 
of time will result from the method. 1st. The primary 
I 
