504 TARS AND EMPYREUMATIC OILS 



anthracene, and pitch may be mentioned. For further details see 

 Martin, ' Industrial Chemistry, Organic,' p. 415. 



Uses. The chief medicinal use of coal-tar is as an antiseptic 

 appli cation in certain skin diseases. 



JUNIPER-TAR OIL 

 (Huile de Cade, Oil of Cade, Oleum Cadinum) 



Source, &c. Juniper-tar oil is obtained by the destructive dis- 

 tillation of the wood of Juniperus Oxycedrus, Linne (N.O. Coniferce) ; 

 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, &c.) 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 down- 

 wards 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. 



Description. 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). 



Constituents. The composition of juniper- tar oil is but very 

 imperfectly known. The chief constituent appears to be a sesqui- 

 terpene, C 15 H 24 , boiling at 250 to 260. Cadinene, C 15 H 24 , boiling- 

 point 272 to 275, is also present, but in small quantity. The tar 

 also contains guaiacol, ethylguaiacol, propylguaiacol, creosol, &c., 

 together with acetic acid and its homologues. 



