The official rosin cerate congeals as a perfectly homogeneous mixture upon cooling without stirring, on account of the large proportion of rosin and wax present; stirring of the melted and strained mixture is, in fact, not desirable in this case, as it incorporates considerable air. Rosin cerate gradually grows tougher by age. In cold weather the proportions of lard and yellow wax may be changed with advantage to lard 530 Gm. and yellow wax 120 Gm. in the official formula.

Compound rosin cerate is often called for under the name Deshler's salve. If kept on hand for some time it becomes tough, which condition may be avoided by using olive oil or liquid petrolatum in place of the linseed oil.

Of late years both ointments and cerates have been largely superseded, especially in Europe, by dermatologic pastes and glycerogelatins. The former are mixtures of the medicinal agents with starch, dextrin, or kaolin, and glycerin, soft soap, petrolatum, or lard, and are intended chiefly for antiseptic, astringent, or germicidal effects. As a general vehicle for the preparation of these pastes, a mixture of dextrin, glycerin, and distilled water, equal parts by weight, may be brought into solution with the aid of heat, and sufficient water finally added to restore any loss by evaporation. Ichthyol, naphthol, resorcin, salicylic acid, sulphur, and zinc oxide are the more important remedial agents used in the form of pastes, the proportions being varied to suit particular cases. The glycerogelatins are firmer than the pastes, and must be melted before they can be applied to the affected parts, which latter is done by means of a soft brush. The vehicle consists of a mixture of gelatin, glycerin, and water, made in proportions ranging from 5, 20, and 65 parts to 15, 45, and 25 parts of the respective constituents. medicating agents, chrysarobin, ichthyol, iodoform, resorcin, salicylic acid, and zinc oxide are added singly or in combination.

As

Another form of modern dermic medication is by means of pencils, of which the following formula serves as an example: salicylic acid 10 parts, powdered tragacanth 5 parts, starch 30 parts, dextrin 35 parts, sugar 20 parts, distilled water sufficient to make a paste, which is rolled out into rods about 5 millimeters (inch) in diameter and 5 centimeters (2 inches) in length. The pencils are dried at ordinary temperature on parchment paper and wrapped in tinfoil.

The official kaolin poultice, Cataplasma Kaolini, is often used in place of ointments as a cooling antiseptic dressing. It is made by mixing finely powdered boric acid 45 Gm. with finely powdered kaolin (previously heated for an hour with frequent stirring on a boiling-water bath) 577 Gm., then incorporating the mixed powders with glycerin 375 Gm., and finally adding thymol 0.5 Gm., oil of peppermint 0.5 Gm., and methyl salicylate 2 Gm. This cataplasm is a stone-colored homogeneous mass, which should be preserved in air-tight containers on account of its tendency to absorb moisture from the air.

CHAPTER XXXIV.

LINIMENTS AND OLEATES.

THESE preparations are closely allied to those described in the preceding chapter, being also intended only for external use.

LINIMENTS.

Liniments are fluid or semifluid preparations, usually in the form of solutions, although in some instances merely mechanical mixtures, the solvent or vehicle being either a fixed or volatile oil or alcohol, which latter is sometimes mixed with water. They are always applied to the skin with friction, and, when mechanical mixtures only, require to be well agitated before they are applied. For endermatic medication liniments are in many cases to be preferred to ointments, because, being applied with friction, the medicinal agents are more likely to be readily absorbed by the unbroken skin. For this purpose it is essential that the vehicle be of a volatile or fatty character, since non-volatile substances in aqueous solution are either not absorbed at all or only to a slight extent, while the same substances dissolved in alcohol, chloroform, or ether are quickly taken up, as shown by their prompt appearance in the secretions. The Pharmacopoeia recognizes 8 liniments, of which 4 are of a fatty nature, while 4 are alcoholic or hydro-alcoholic solutions; with 2 exceptions, they are usually prepared extemporaneously, although they keep well.

When fixed oils are shaken with aqueous solutions of alkalies, partial decomposition of the fat takes place, and an emulsion-like mixture results, in which the remaining oil is kept in perfect suspension by the newly formed soap; such liniments thicken considerably by age, which it is intended to provide against in the official formula for ammonia liniment by the addition of alcohol. If the fixed oils used are fresh and perfectly sweet, they are but little acted on by alkalies in the cold, hence the preparation of a perfect liniment becomes difficult.

The following is a list of the official liniments:

The use of cottonseed oil alone for the preparation of ammonia liniment has not been satisfactory, separation into two distinct layers invariably occurring in the mixture, and while the addition of about

20

per cent. of common olive oil for a like quantity of the cottonseed oil was found to improve the condition on account of the free fatty acids generally present in the lower grades of olive oil, the present official formula directing the addition of a small quantity of oleic acid is preferable. The acid unites with the ammonia, forming a soap, ammonium oleate, which materially aids in emulsionizing the cottonseed oil. The presence of 5 per cent. of alcohol is intended to prevent undue thickening of the liniment if kept on hand for some time.

In the preparation of camphor liniment, the solution of the camphor can be materially hastened by placing it, with the oil, in a strong bottle and, after corking the same securely, digesting the mixture on a water-bath at a moderate heat.

The official belladonna liniment is decidedly the most efficient preparation of that drug for external use, but owing to its potent character and ready absorbability serious results may occur from its liberal use. Both the alcohol and camphor aid absorption, and it should never be dispensed except on a physician's prescription.

The chloroform liniment of the United States Pharmacopoeia differs materially from that of the British Pharmacopoeia; the latter is a mixture of equal volumes of chloroform and camphor liniment. A very popular preparation, known as Compound Chloroform Liniment, is composed of 1 volume each of chloroform and tincture of aconite and 6 volumes of soap liniment.

Dried soap, as directed in the Pharmacopoeia, is to be much preferred in making soap liniment, on account of the variable quantity of moisture present in the official soap. The present official directions yield a very satisfactory product with little expenditure of time. The soap is readily dissolved in the boiling water, and if the alcohol be added to the gelatinous mass, while the latter is still warm, a clear solution is obtained very soon. The official directions to set the liniment aside in a cool place for twenty-four hours, and then to filter, are for the purpose of getting rid of the sodium palmitate always present in Castile soap, which is but sparingly soluble in the menstruum, particularly in the cold.

The official turpentine liniment is also known as "Kentish" liniment; only a moderate heat should be employed to melt the rosin cerate, so as to avoid volatilization of the oil of turpentine, which must also be added in small quantities, with constant stirring, until a smooth, uniform, opaque mixture results.

Closely allied to the liniments are the infused oils, made by digesting 20 Gm. of an alkaloidal drug, previously macerated with ammoniated alcohol, with a mixture of 50 Cc. each of cottonseed oil and lard oil until the alcohol has been vaporized. The active principles of the drug are intended to be taken up by the oils, together with green coloring-matter.

The so-called drying liniments or medicated varnishes consist of mucilage of tragacanth, starch or dextrin, with egg-albumen, suitably medicated, which when applied to the skin leave a thin varnish or protective film, similar to that obtained with collodion.

OLEATES.

This class of preparations has been in use by physicians in this country since 1872. Normal oleates are true chemical compounds of oleic acid with metallic oxides or alkaloids, but the oleates medicinally employed are simply mixtures of such normal oleates with oleic acid or some other diluent. The proportion of any particular metallic oxide or alkaloid to be dissolved in oleic acid may vary with the views of the physician; but in the case of normal oleates a certain proportion cannot be exceeded. The expressions 2, 5, 10, or 20 per cent. oleate are used to indicate that 2, 5, 10, or 20 parts of the respective alkaloid or metallic oxide are present in every 100 parts of the finished product. The following table shows the amount of base combined with oleic acid in 100 parts of the respective normal oleates:

From these normal oleates weaker preparations can readily be made by admixture with the desired diluent, according to the following rule: multiply the required quantity by the required percentage strength and divide the product by the percentage of the normal oleate; the quotient will indicate the quantity of normal oleate to be used, and subtracting this from the required quantity gives the weight of the diluent necessary.

Solutions of alkaloidal oleates are best prepared by triturating the prescribed quantity of dry alkaloid in a small dish with the necessary weight of oleic acid, and heating the mixture on a water-bath until perfect solution results; they are, as a rule, of 2 per cent. strength, with the exception of morphine and cocaine, usually of 5 per cent. strength, and quinine, frequently prescribed of 25 per cent. strength. At one time it was thought that oleates could produce systemic effects, but numerous experiments have shown this idea to have been erroneous. Nevertheless they have been found very useful for local medication, both on the skin and by penetration into the skin. Alkaloidal oleates are always liquid preparations, being solutions of the respective normal alkaloids in an excess of oleic acid. The necessary amount of alkaloid and acid for any given weight of solution can be quickly calculated by the rules given on page 125, under Percentage Solutions.

The solution of metallic oxides in oleic acid is effected very slowly even with the aid of heat; hence they are preferably prepared by mutual decomposition, by adding an aqueous solution of the metallic salt to a solution of an alkali oleate. The precipitated metallic oleates are then washed with water to free them from the newly formed alkali salt, preferably with hot water, two or three washings being sufficient; but for mercuric oleate only warm water must be employed, to avoid decomposition. Metallic oleates are usually prepared of normal strength, as they keep better in this form and can be subsequently diluted as wanted. Benzoinated lard or soft paraffins may be employed as diluents when the oleate is intended for epidermatic use, or lanolin when an endermatic effect is desired, as the latter substance is more readily absorbed by the skin.

A solution of castile soap is very often used as the alkali oleate in the preparation of metallic oleates, especially those of lead, copper, and zinc; but since the soap is a sodium oleopalmitate instead of pure sodium oleate, the resulting metallic oleates will also be contaminated with palmitates; in practice, this slight impurity is generally disregarded, and can be reduced to a minimum by allowing the soap solution to stand in a cool place for twenty-four hours and then filtering. The strength of the soap solution generally used