This section is from the book "Materia Medica Pharmacy, Pharmacology And Therapeutics", by W. Hale White. Also available from Amazon: Materia Medica Pharmacy, Pharmacology And Therapeutics..
Emplastrum Plumbi. Lead Plaster. This is lead oleate, and is sometimes called Diachylon Plaster. Lead Oxide, 3200, is boiled in water, and Olive Oil, 6000. When the mass has acquired a whitish color and is perfectly homogeneous, it is well kneaded to remove the Glycerin and divided into rolls of suitable size. 3PbO+ 3H2O+2(C3H5(C18H33O2)3)=3(Pb2(C18H33O2)2)+2(C3H5(OH)3).
Lead Oxide or its Plaster is contained in Emplastrum Ammoniaci cum Hydrargyro, Ferri, Hydrargyri, Opii, Resinae, and Saponis.