Emplastrum Saponis Fuscum.—Brown Soap Plaster.
SYNONYMS: Emplastrum cerati saponis, Soap cerate plaster.
Preparation.—Boil together by means of a steam bath, lead oxide, 15 ounces (av.), and vinegar, 1 gallon (Imp.), with constant stirring, until the acid and the oxide combine. Add powdered curd soap, 10 ounces (av.), and again boil the mixture until the greater portion of the moisture is dissipated. Lastly, add yellow wax, 12 ½ ounces (av.), and olive oil, 1 pint (Imp.), previously melted together. With constant stirring maintain the heat until the remaining moisture has sufficiently evaporated to give a plaster consistence to the product. This product is in reality a cerate, and is the same as the Ceratum Saponis Compositum of the London Pharmacopoeia. A similar preparation is that of the U. S. P. (1870), as follows: Take of soap plaster, 2 troy ounces; white wax, 21 troy ounces; olive oil, 4 troy ounces. Melt together the plaster and the wax, add the oil, and after continuing the heat a short time, stir the mixture until cool—(U. S. P., 1870).
Gerrard proposes the substitution of acetic acid (18 ounces) in place of the vinegar. This quickens the process by shortening the time required for boiling.
Action and Medical Uses.—This plaster is employed where a cooling sedative cerate is desired. It is adapted to chronic inflammatory swellings, as of scrofula, arthritic enlargements, etc. It also serves as an adhesive plaster.