This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Soap: a composition of oils or fats with al-kaline salts, incorporated so as to dissolve together in water into a milky semitransparent liquid.
I. Sapo durus.
Hard soap. The fined hard soap is prepared with fresh-drawn oil of almonds, by digesting it with thrice its measure of the soap-lyes, formerly described (see Sales alka-lini) in such a heat that they may just fimmer. In a few hours they unite into a turbid fluid, which, on being boiled a little, becomes more transparent, and ropy, so that if a little be suf-fered to cool, it will concrete like jelly. Some sea salt is now thrown in, till the boiling liquor loses its ropiness; and the coction continued till, on receiving some drops upon a tile, the soap is found to coagulate, and the water to freely sepa-rate from it. The fire being then removed, the soap rises gradually to the surface; from whence it is taken off before it grows cold, and put into a wooden mould, or frame, with a cloth bottom: being afterwards separated from the mould, it is set by till it has acquired a due consistence. After the same manner a hard soap is made with oil-olive, which mould be of the fined kind, that the soap may prove as little ungrateful as possible either to the palate or sto-mach. By the same or similar processes this commodity is prepared for common uses in the way of trade. The finest of the common soaps is that called Spanish or Castile soap, which is made with oil-olive, and the alkaline salt called soda or barilla: our soap-boilers find that this alkali gives a better consistence, or greater hard-ness to the soap, than the other potashes or common vegetable alkalies.
Hard soap, triturated with vegetable resins and thick balsams, incorporates with them into a compound, soluble, like the soap itself, in watery liquors: hence it proves an useful ingredient in resinous pills, which of themselves are apt to pass entire through the intestines, but by the admixture of soap become dissoluble in the stomach. It renders unctuous and thick mucous animal matters dissoluble in like manner in aqueous fluids, and hence may be presumed to act as a menstruum for these kinds of sub-stances in the body, that is to attenuate viscid juices and resolve obstructions: such, in effect, are the virtues which it appears to exert in cachectic, hydropic, and icteric cases, in which last, particularly, its aperient and resolvent powers have been often experienced. Solutions of it have been found likewise to dissolve certain animal concretions of the harder kind, as the filaments which are sometimes seen floating in the urine of rheumatic and arthritic persons, the matter secreted in gouty joints, and the more compact urinary calculus: on these substances (at lead on the latter) though soap of itself acts more languidly than lime-water, yet when joined to that menstruum it remarkably increases its activity, the dissolving power of a composition of the two being, according to Dr. Whytt's experiments, confi-derably greater than that of the soap and lime-water unmixed: of the good effects of these medicines in calculous cases there are several instances; but what their effects may be in gouty and rheumatic ones, is not yet well known.
Sapo Ph. Lond. mat. med.
Sapo albus hispanus Ph. Ed. mat. med.
The usual dose of soap, as an aperient, is half a dram or a dram: as a lithontriptic, half an ounce, or an ounce, or more, are taken in a day at proper intervals. It is given in the form of a bolus or pills; or made into an electuary with some grateful syrup, as that of orange peel; or dissolved in milk or other liquids. * It is excellently covered by chocolate: two drams in a pint are not in the least perceived; the chocolate is thought by some better than without it. A little soap is always added in the composition of chocolate, to make it froth.
In watery liquors it dissolves only imperfectly, the solution being always turbid. Rectified spirit, though it has no action on the alkaline salt or oil separately, dissolves the soap into a limpid liquor. Proof spirit, free from acidity, dissolves it as perfectly, and in much larger quantity; rectified spirit not taking up one tenth its own weight, but proof spirit one third or more. The spirituous solutions bear to be largely diluted with pure water, without suffer-ing any turbidness or separation of their parts: but on the addition of any acid, or of any combination of acids with earthy or metallic bodies, as the sal catharticus amarus, etc. the soap is resolved into its constituent ingredients; its alkaline salt being absorbed by the acid, and the oil rising to the surface. The oil, thus extricated from soap by acids, disolves like essential oils, in rectified spirit.
Soap is employed externally for discussing rheumatic pains, arthritic tumours, the humours stagnating after sprains, etc. Some pretend that the indurated tophaceous concretions in arthritic joints have been resolved by the external use of soapy cataplasms. Several com-positions for external purposes are prepared in the shops. One part of Spanish soap, sha-ved or cut in thin slices, is stirred into six parts of common plaster melted over the fire, and the mixture boiled till it acquires the consistence of a plaster; which is formed into rolls whilst hot, the soap disposing it to grow brittle as it cools †: some endeavour to promote the resolvent virtue of the soap, by adding to four parts of the common plaster, two of gum plaster, with one of soap ‡. But soap acts to much better advantage in the form of a cataplasm or liniment, than in the stiffone of a plaster. The officinal saponaceous liniments are made, by digesting three ounces of Spanish soap in a pint of spirit of rosemary till the spirit is saturated, and dissolving in this solution an ounce of camphor ||: or by digesting two ounces of soap in a pint of rectified spirit of wine, and afterwards adding an ounce of camphor, and two drams of oil of rosemary §. Sometimes opium is joined, by which the compound is supposed to be rendered more effectual for allaying violent pains: half an ounce of opium is digested with the soap in the last mentioned composition. This is given also internally, in nervous colics, jaundices, etc.
Emplaftrum faponis † Ph. Lond.
2. Sapo mollis. Soft foap. The common soft soap used about London, generally of a greenish hue with some white lumps, is prepared chiefly with tallow: a blackish sort more common in some other places, is said to be made with whale oil. Both kinds are considerably more acrid than the hard soaps, and are employed only for some external purposes: a mixture of equal parts of our common soft soap and quicklime is used as a mild caustic.
3. Sapo volatilis. Volatile soap. Of this there are three kinds: one composed of fixt alkalies and volatile oils; another, of volatile alkalies, and oils of the grosser or more fixt kind; and the third, in which both the alkali and the oil are volatile.
Fixt alkalies are very difficultly made to unite with distilled oils. The most commodious method of obtaining the combination appears to be, by throwing the salt red-hot into a heated mortar, immediately reducing it into powder, then pouring on it, while it continues quite hot, by little at a time, an equal quantity or more of the oil, and continuing to grind them together, so as to form a smooth soft mass. Stahl reports that the union may soon be obtained also, by agitating the salt with a small proportion of the oil, and a quantity of phlegmatic vinous spirit; the spirit seeming to serve as a medium for joining them together. This medicine, prepared with oil of turpentine, was formerly celebrated as a diuretic, in nephritic complaints, and as a corrector of certain vegetables, particularly of opium: its virtues have not been fully determined by experience, nor does the present practice pay any regard to it. Beaume observes, that it consists of only the refinous part of the oil united with the alkali; that the more fluid and well rectified the oil is, the less soap is obtained; and that by adding a little turpentine in substance, the preparation is considerably expedited.
Emp. fapo-nac. † Ph.Ed.
Linimentum saponis || Ph. Lond.
Vulgo Balf. faponaceum § Ph. Ed.
Linimentum anodynum vulgo Balf. anodyn. Pb, Ed.
Combinations of volatile alkalies with ex-pressed oils, and with the oily balsamic juices, are obtained more readily. One ounce of spirit of sal ammoniac, and three of oil of olives, shaken together in a wide-mouthed vial, unite perfectly, in a short time, into a white sapo-naceous liquid: or, for a more active preparation, one ounce of the volatile spirit with quicklime is shaken with two ounces of olive oil. Both these compositions are very acrimonious, and are used only externally, as sti-mulants, in rheumatic and ifchiadic pains.
Combinations of volatile alkalies with volatile oils, in a liquid form, have been already mentioned under the head of sal alkalinus volatilis: compositions of the same kind may be obtained in a solid state, by mixing the salt with the oil, and subliming them together. It may be ob-served, that in all these combinations made with volatile salts, though the pungency of the salt is more or less covered, it is never completely sheathed as that of the fixt alkalies is in the hard soaps; and that none of the compositions, in which either the alkali or the oil is volatile, are so perfectly saponaceous as those in which they are both of the more fixt kind.
Sapo philo-fophicus tar-tareus, etc.
Linim. am-moniae fortius Ph. Land.