This section is from the book "A Text Book Of Materia Medica, Being An Account Of The More Important Crude Drugs Of Vegetable And Animal Origin", by Henry G. Greenish. Also available from Amazon: A Text Book of Materia Medica : Being an Account of the More Important Crude Drugs of Vegetable and Animal Origin.
Juniper-tar oil is obtained by the destructive distillation of the wood of Juniperus Oxycedrus, Linne (N.O. Coniferoe); it is prepared chiefly in the mountains in the south-east of France, in the departments of Alpes Maritimes, Var, and Gard.
Selected portions of the trunk of the tree are cut into small pieces, and placed in a crude distilling apparatus consisting of an iron pot inverted over a concave stone slab, from the centre of which a pipe leads downwards. The smaller pieces of wood are used to heat the iron pot, and the distillate which passes down the delivery pipe is collected and allowed to stand for several weeks. At the end of this time it will have separated into three distinct layers, viz. a heavy, tarry mass, an aqueous liquid, and a lighter dark oily layer. The latter, which is true huile de cade, is separated and conveyed to neighbouring towns (Nismes, Avignon, etc.) for sale.
More recently the distillation has been conducted in a brick kiln about 20 feet long and 6 feet high, the bottom of which slopes downwards and has a gutter to carry off the tar. The kiln is filled with the wood which is then fired and the openings closed. The distillation lasts several days.
Juniper-tar oil is a dark reddish brown or nearly black liquid, with a tarry, but by no means disagreeable, odour, and a bitter, acrid taste. It is less viscid than wood-tar, having an oily consistence. The specific gravity is usually rather less than that of water (about 0.990), but in some (old) specimens it is rather higher. It is completely soluble in ether and chloroform, partially in cold but almost completely in boiling alcohol. Water shaken with it dissolves but little, acquiring a yellowish colour and an acid reaction (distinction from coal-tar).
The composition of juniper-tar oil is but very imperfectly known. The chief constituent appears to be a sesquiterpene, C15H14, boiling at 250° to 260°. Cadinene, C15H14, boiling-point 272° to 275°, is also present, but in small quantity. The tar also contains guaiacol, ethylguaiacol, propylguaiacol, creosol, etc, together with acetic acid and its homologues.
Juniper-tar oil is used as an application in various skin diseases.
Pine-tar is best detected by the following test: - Shake 1 c.c. of the oil vigorously with 15 c.c. of petroleum spirit and filter; to 10 c.c. of the filtrate add 10 c.c. of a 5 per cent. solution of copper acetate; allow separation to take place and dilute 5 c.c. of the upper layer with 10 c.c. of ether. Pure oil of cade gives a pale, brownish yellow colour, pine-tar an intense green.
When fractionally distilled, from 68 to 80 per cent. should distil between 150° and 300° (pine-tar about 15 per cent.).
Birch tar (Oleum Rusci, Oleum Betulae empyreu-maticum) is a nearly black tarry liquid obtained in Russia by destructive distillation of birch wood (Betula alba, Linne). It possesses the characteristic odour of Russian leather and has been used in skin diseases.