ON LEAD PLASTER. 
271 
liquid operated on. To confirm this, it is only necessary to 
evaporate to dryness the liquor treated by copper and hydro- 
chloric acid; calcine the residue, and dissolve in nitric acid, 
and a considerable amount of distilled water. A solution 
will be obtained, which will readily demonstrate the presence 
of copper, by means of ammonia, clean iron, and ferrocy- 
anide of potassium. 
Journ. de Chim. Med. 
ART. LXVI.— PRACTICAL OBSERVATIONS ON LEAD 
PLASTER. 
By Davallon, 
Professor in the School of Medicine and Pharmacy, at Lyons. 
The great consumption of lead plaster has led to consider- 
able attention to practical modifications in the process of 
its manufacture. 
In the Journal de Pharmacie de Midi, my friend M. E. 
Manchon, has published some interesting details on this 
point ; but his conclusions are in opposition to the observa- 
tions which I have made on this preparation. 
The principal constituents are lard, olive oil, litharge, and 
more or less water ; this latter serving not only as a water 
bath to prevent too great a rise of temperature, but also to 
favor the reaction between the oxide of lead and the oil. 
On consulting the older works on pharmacy, it will be 
perceived that the precise amount of water is not deter- 
mined, but all agree in separating as much as possible all 
which remains in the plaster without being combined. 
