PIX ABIETINA.[[599]] L. (Pinus Abies. Resina Præparata.)
Pix Burgundica. E.D. Burgundy Pitch.
This substance is procured by making incisions through the bark of the Norway Spruce fir, and afterwards boiling the flakes so obtained in water, and then straining the resin through coarse cloths under a press; whereas frankincense (Abietis resina) is a spontaneous exudation from it. It is now entirely confined to external use, as a rubefacient spread on leather; it is very adhesive. Emplast: Picis comp. L. Emplast: Picis Burgund. D. Adulterations. A factitious sort, manufactured in England, is often met with; it is to be distinguished by its friability, and its want of viscidity and unctuosity, and by the absence of that peculiar odour which characterises the genuine specimens.
PIX LIQUIDA. L.E.D. (Pinus Sylvestris.) Tar.
This fluid is formed from the decomposition of the resinous juice of the pine, during the slow and smothered combustion of its branches, and as a summary definition of the substance, that by Pliny cannot be surpassed, “Pix nihil aliud quam combustæ resinæ fluxus.” Lib. 23. c. 1. Chemical Composition. It is found to consist of empyreumatic oil, resin, acetic acid, and some salts. Solubility. Water readily dissolves a portion of Tar, and forms a solution of the colour of Madeira wine, with a sharp empyreumatic taste. Med. Uses. Tar water, under the auspices of Bishop Berkley, was formerly considered a remedy of extraordinary powers;[[600]] this opinion however has at length passed away, (see page 27.) and Tar is now particularly indebted for a place in the Materia Medica, to an essay by Sir Alexander Crichton, entitled, “An Account of some Experiments made with the Vapour of boiling Tar,[[601]] in the cure of Pulmonary Consumption.” At the request of Sir Alexander, I was induced to make a trial of its effects, and I do not feel any hesitation in stating that the result has led me to believe that it may, in some cases, be attended with benefit. In the application of the remedy several precautions are necessary for its success. The Tar employed should be that used in the cordage of ships; to every pound of which half an ounce of sub-carbonate of potass must be added, in order to neutralize the pyroligneous acid generally found mixed with the tar, the presence of which will necessarily excite coughing; the tar thus prepared is to be placed in a suitable vessel over a lamp, and to be kept slowly boiling in the chamber during the night as well as the day; the vessel however ought to be cleaned and replenished every twenty-four hours, otherwise the residuum may be burnt and decomposed, a circumstance which will occasion increased cough and oppression on the chest. The ancients entertained a high opinion of the efficacy of Tar in pulmonary diseases, when internally administered; supposing it to promote expectoration, relieve dyspnæa, and check spitting of blood; Dioscorides particularly speaks of its utility in such cases; he also recommends it to be applied to ulcers, which he says it fills up and heals, whether they be situated on the surface of the body, or in the ears, throat, and other internal parts. See the chapter on “Inhalations,” page 202. Officinal Prep. Unguent. Picis Liquidæ. L.
PLUMBI SUB-CARBONAS. L.
Carbonas Plumbi, vulgo Cerussa. E.
Cerussa, Sub-acetas Plumbi. D.
Cerusse, or White Lead.
Chemical Composition. The composition of this substance has not until lately been well understood, and hence the different appellations bestowed upon it by the different colleges. Solubility. It is insoluble in water, but soluble in pure potass. Uses. It is only employed externally, by sprinkling on excoriated parts; the safety of such a practice however is questionable. Officinal Prep. Unguent. Ceruss. D. Plumbi Acetas L.E.D. (K) Adulterations. Chalk may be detected by assaying its solution in cold acetic acid with oxalate of ammonia; Carbonate of barytes, by adding to a portion of the same solution, sulphate of soda very largely diluted with distilled water; and Sulphate of barytes, or Sulphate of lead, by the insolubility of the white lead in boiling distilled vinegar.