Medicinal oleates are, according to Dr. J. D. Shoemaker, definite chemical compounds or salts, having no excess of either their acid or basic radicals, and Dr. Lawrence Wolff finds that the best and readiest method of preparing oleates is by the double decomposition of sodium oleates with solutions of neutral salts. The sodium oleate is made by the saponification of oleic acid with sodium hydrate. Dr. Squibb, howeve, is of the opinion, that in the preparation of oleates, none are so good as those made by the direct union of the acid with the dry base, without heating, and that the preparation should always be either a liquid or semi-solid which is easily and completely liquefied by the natural temperature of the surface to which it is applied; and he further says that in the rare cases where the excess of acid as a solvent of the oleates proves an irritant to the skin, dilution with a bland oil becomes admissible. The most common oleates in use are those of mercury, zinc, lead, copper, aluminum, bismuth, iron, arsenic, silver, aconite, atropine, morphine, veratria and strychnine. Oleates of the more active alkaloids, namely, aconitia, atropia, strychnia and veratria, are usually made of the strength of two per cent. of the alkaloid; the oleate of morphia usually contains five per cent. of the alkaloid; the oleate of quinine usually contains twenty per cent. of the alkaloid. Dr. Squibb says that all of these are very simply and easily made by putting the weighed quantity of the alkaloid into a mortar, adding a small quantity of the oleic acid, little by little, and triturating until the alkaloid is completely dissolved. The strong solution thus made is then poured into a tarred bottle, and the mortar and pestle rinsed twice into the bottle with small quantities of oleic acid. The proper weight is then made up by the addition of oleic acid.

According to the preparation of oleates as recommended by Dr. Shoemaker -

Oleate of Mercury is prepared by precipitating a solution of sodium oleate with mercuric chloride, and is the best local stimulant and alterative application of all the mercurials. It may be diluted with either the paraffinates, or, better still, with lard or lard oils. When applied to the unbroken skin it causes marked stimulation, bordering on congestion. It has great penetrating power, is readily absorbed by the skin, and does not become rancid nor stain the linen. It is a valuable remedy in syphilis, the treatment of indurations after abscesses, skin diseases of a scaly nature, obstinate ulcers, parasitic affections, etc., and may be employed advantageously with other oleates. As it is capable of producing the constitutional effects, it must be employed carefully.

A mixture of oleate of mercury gr. x to xx, with the ointment of oleate of zinc Oleates 1239 is very effective in chronic acne and eczema, especially in the fissured variety of the latter common to the palmar and plantar surfaces. For syphilitic skin eruptions and in superficial ulcers, oleate of mercury with oleate of bismuth or the same quantity of the ointment of the oleate of lead, acts promptly and efficiently. For one of the best and most efficacious oily applications for loss of hair, especially when the scalp is harsh and dry, and the hairs dull and without lustre, a preparation composed of oleate of mercury to ij, with oil of ergot is highly recommended.

Oleate of Zinc is prepared by decomposing a sodium oleate with a saturated solution of zinc sulphate, boiling out and drying the precipitate and then reducing it to an impalpable powder. One part of oleate of zinc melted with three parts of lard or oil gives a most useful ointment, but the best results are obtained from the oleate of zinc alone. It is in the form of a fine, pearl-colored powder, having a soft, soapy feel, much like powdered French chalk. It is valuable in all forms of sweating.

Oleate of Lead is prepared by precipitating a sodium oleate with a solution of lead subacetate. To form the ointment of lead oleate, the washed and dried precipitate is melted with equal parts of lard. Oleate of lead exerts a combined sedative and astringent action when applied to denuded skin, and also arrests morbid discharges, protects the surface and allays irritation. It is useful in eczema, acne and other skin diseases. For skin diseases, oleate of lead Oleates 1244 with oleate of bismuth is very effectual, especially in the fissured form of palmar and plantar eczema; and when the cracking is very deep, to cause stimulation, oil of cade gtt. xx to xxx may be added. In scabies oleate of lead with sulphur is an excellent application.

Oleate of Aluminum is prepared by decomposing sodium oleate with aluminum sulphate. The washed precipitate, mixed with equal parts of lard, forms an ointment of a semi-solid, dark-brown color, which is very astringent in its action. It rapidly arrests all muco-purulent discharges, and is an efficient dressing for foul ulcers, sinuses, burns and scabs.

Oleate of Bismuth is prepared by first obtaining crystallized bismuth nitrate, and dissolving it in glycerine and decomposing with this the sodium oleate. It is of the consistence of ointment, and of a pearly-gray color and a soft, bland substance. It has an emollient and somewhat astringent action, and is an excellent application for relieving cutaneous irritation. In pustular eruptions, especially sycosis, it is a useful application; also in superficial erysipelas, sunburn and chronic inflammation of a portion of the face.

Oleate of Copper is prepared in a similar way to the oleate of lead, by double decomposition with a saturated solution of copper sulphate. A ten or twenty per cent ointment can be made with either cosmoline, fat or lard. When applied to the unbroken skin, it penetrates deeply, and causes a slight stimulation; and when applied to broken skin, it coats it with an insoluble albuminate. It is very efficient for ringworm, and in the most obstinate cases usually affects a cure. It is also used with advantage on indolent ulcerated surfaces, and with effect on hard, horny warts and corns.

Oleate of Arsenic is obtained from arsenious chloride, made by the careful saturation of hydrochloric acid with arsenic. This solution is mixed with sodium oleate, when the arsenic oleate is precipitated. In the proportion of gr. xx to an ounce of fatty base, it forms oleate of arsenic ointment, which is soft and yellow, having no action on the skin. When applied to wounds, or ulcerating surfaces, it destroys the tissue to some depth. It is used in lupus, the ulcerating variety of epithelioma, and, after scraping the surface, to destroy warts, corns, old granulations, etc. It may be combined with arnica, opium, belladonna or hyoscyamus. A number of other oleates are in use, among them Nickel oleate, which is a greenish, waxy mass, used in the form of an ointment, containing from five to fifteen grains to the ounce of lard, is astringent and somewhat escharotic, and useful for hard, horny, granulating surfaces; Silver oleate, a brownish, pulverent substance, and, in the form of ointment, valuable for application to ulcers, erysipelas, etc.; Cadmium oleate, a yellowish-white mass, and in the form of ointment (five to fifteen grains to the ounce), has an astringent and escharotic action, and is useful in glandular enlargements and thickening of the integument.