Oleates, Fr.; Oleate, G.
The oleates are a class of preparations which were introduced to the medical profession by John Marshall, F.E.S., in 1872. They are usually solutions of certain bases in oleic acid, and are made by triturating the solid substance with the oleic acid until it is dissolved. Whenever it is possible, the application of heat should be avoided, and it has been observed that the freshly precipitated oxides of the metals dissolve more readily than those which are old. The title oleate is probably the best that could be devised, although it must be understood that, as found in the Pharmacopoeias, they are not pure chemical compounds, but merely compounds of the oxides or the alkaloids, as the case may be, with oleic acid dissolved in a great excess of the latter.
Oleates may be made either by direct combination of the ingredients or by double decomposition. When made by the latter method, a good quality of oleic acid should be treated with the proper quantity of solution of sodium hydroxide, to saponify it, any excess of the alkali being neutralized with a little tartario acid. This soap solution is preferably used diluted.
J. M. Good, in making the oleates of the alkaloids, proposes the use of sufficient oleic acid to dissolve the alkaloid and then diluting the solution with a bland fixed oil, such as almond oil. (Proc. Missouri Pharm. Association, 1891, p. 65.)
The medicinal properties of the oleates are, of course, dependent upon the base, so that these preparations may be considered the equivalents of the corresponding ointments, over which, however, they have certain advantages. They are much cleaner and more elegant in appearance. They seem to be more irritating than the ointments, and, unless diluted with an equal bulk of cottonseed, olive, or other bland oil, are, when applied with friction, likely to provoke a cutaneous eruption or even pustulation. Marshall recommends that they be applied with a brush, or gently spread over the part with the finger.