This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Pix Liquida Pharm. Lond. & Edinb. Tar: a thick, black, resinous, very adhesive juice; melted out by fire from old pines and fir-trees. The trees, cut in pieces, are inclosed in a large oven, which being heated by a fire on the outside, or the wood itself kindled and smo-thercd, the juice runs off by a canal at the bottom.
Tar differs from the turpentine or native resinous juice of the trees, in having received a disagreeable empyreumatic impression from the fire; and in containing, along with the pungent bitter terebinthinate matter, a portion of the acid which is extricated from the wood by the heat, and likewise of its gummy or mucilaginous matter. By the mediation of these principles, a part of the terebinthinate oil and resin becomes dissoluble in watery liquors, which extract little or nothing from the purer turpentines.
Water impregnated with the more soluble parts of tar has been recommended as a remedy for almost all diseases. The proportions that have been commonly followed are, two pounds of tar to a gallon of water; which are to be well stirred together, then suffered to settle for two days, and the clear liquor poured off for use. It is observed, that "tar water, when right, is "not paler than French, nor deeper coloured "than Spanish white wine, and full as clear: "if there be not a spirit very sensibly perceived "in drinking, the tar-water is not good. It "may be drank either cold or warm. As to "the quantity, in common chronical indispo-"sitions a pint a day may suffice, taken on an "empty stomach, at two or four times: more "may be taken by strong stomachs. But those "who labour under great and inveterate mala-"dies, must drink a greater quantity, at least "a quart every twenty-four hours. In acute "diseases, it must be drank in bed warm, and "in great quantity (the fever still enabling the "patient to drink perhaps a pint every hour." Though this medicine is undoubtedly very far inferiour to the character that has been given of it, it is apparently capable of answering important purposes, as a deobstruent balsamic solu-tion, moderately warm and stimulating. It sensibly raises the pulse, and increases either perspiration or the grosser evacuations. I have been informed of some late instances of its good effects in disorders of the leprous kind.
Some have imagined the acid to be the principle that gives virtue to tar-water; and hence have endeavoured to introduce, instead of the infusion, an acid spirit extracted from tar by distillation. But the effects of this, as of other acids, are opposite to those experienced from tar-water: nor does the acid of tar differ from that which is extricated by fire from all kinds of recent wood. Tar-water, distilled, yields a liquor very considerably impregnated with its flavour, though more grateful than the infusion itself both in smell and taste: there remains a light, spongy, blackish substance, not acid but bitter, partially dissoluble again in water.
This juice is sometimes given also in substance, mixed with so much powdered liquorice, or other like powdery matters, as is sufficient to render it of a due consistence for being formed into pills. An ointment, made by melting it with an equal weight of mutton suet, and straining the mixture whilst hot†, or by melting together five parts of tar and two of yellow wax‡, is sometimes used as a digestive, and said to be particularly serviceable against scorbutic and other cutaneous eruptions.
Pil. piceae Nofocom. Ed.
On infpiffating tar, or boiling it down to dryness without addition, it gives over an acid liquor in considerable quantity, and an ethereal oil of the same general nature with that of turpentine, but impregnated with the empyreumatic flavour of the tar. The solid residuum is the common pitch, pix arida. Pix sicca, palimpissa dioscoridis C. B. This is less pungent, and less bitter than the liquid tar, and used only in some external applications, as a warm adhesive resin-ous substance. Neumann observes, that when melted with oils, resins, and fats, into ointments and plasters, the pitch is greatly disposed to separate and precipitate.