257 PINUS SYLVESTRIS 



to circumstances (more especially from the size of the stacks), 

 from one to four weeks ; and the amount of tar thus obtained 

 by this rude process is from 7 to 8 per cent. An improved and 

 more rapid method for obtaining tar by distillation in properly 

 constructed stills, has recently been introduced into Bussia, by 

 which more than twice this amount of tar can be obtained. 



The amount of tar imported into Great Britain in 1872 was 

 189,291 barrels, of which 145,483 barrels were shipped from 

 Russian ports. A barrel usually contains about 30 gallons. 



General Characters and Composition. Tar is a viscid, semi- 

 liquid, brownish-black substance, with a peculiar aromatic odour. 

 Its viscidity is, however, destroyed by heat. When examined 

 by a magnifying lens, colourless crystals of Pyrocatechin may be 

 commonly observed in tar, although in some varieties they cannot 

 be detected. Tar is soluble in alcohol, ether, or chloroform, and 

 in the fixed and volatile oils. Water agitated with it acquires a 

 pale brown colour, sharp empyreumatic taste, and acid reaction. 

 This acid reaction is due to the presence of pyroligneous acid. 

 The vapour of tar is highly inflammable. 



Tar is a very complex substance ; but consists principally of 

 empyreumatic resin, acetic acid, various liquid hydrocarbons, resin, 

 and oil of turpentine. 



Medical Properties and Uses. Tar acts both locally, and 

 internally, as a stimulant. It is also regarded as diuretic, and 

 diaphoretic. Externally in the form of tar ointment or tar 

 water, it has a well-established reputation in some chronic skin 

 diseases, as eczema, psoriasis, lepra, ringworm, and others. 

 Tar ointment has also been found a useful application to foul and 

 indolent ulcers. Tar has likewise been employed successfully 

 as an internal remedy in chronic bronchitis, typhoid fever, and 

 habitual constipation. The vapour from heated tar has been 

 also advantageously used in phthisis, chronic bronchitis, and 

 other pulmonary affections. Tar is also much employed in 

 veterinary practice, in the treatment of thrush in the horse ; foot- 

 rot in sheep ; and various skin affections, &c. 



But a very small quantity of tar is, however, used in medicine. 



