• EMPYREUMATIC OILS, ETC. 379 



cent, of the oil, purified and fractionated. Their boiling points 

 ranged from 1(S1^ to 200*^ C. As a result of the examination of 

 the fractions, the conclusion was arrived at that the principal 

 constituents of birch creosote are guaiacol and creosol, with smaller 

 quantities of cresol and xylenol and probably traces of phenol. 

 The portion insoluble in alkalies boils between 170'^'' and 2S8^, about 

 20 per cent of it being between 170^ and 200^ C. 



The birchwood cresote examined, would, therefore, like that 

 from beechwood, appear to contain two series of homologous 

 phenols ; it is considered probable, however, that the relative 

 quantities of the phenols would vary with the quality of the wood 

 or bark and with the method of distillation. 



Two qualities of oil of Birch tar are prepared by Messrs. 

 Schimmel, of Leipzig, viz., crude and rectified. For the preparation 

 of leather and soaps, and all purposes where the dark colour is not 

 a disadvantage, the former kind should be used ; the rectified oil is 

 considerably weaker in aroma.* 



Besides its use in imparting to leather the characteristic, 

 penetrating and lasting odour, and acting as a preservative against 

 the attacks of insects, the oil has established a reputation in 

 Eussia, Poland and Austria, as a curative in certain conditions 

 oi that intra ctible skin disease to which the general term eczema 

 is applied. 



In the outer bark of Betula Alba a substance was discovered by 

 Lowitz in 1788, to which the name Betulin^ has l)een given. It 

 was considered to belong to a series of resins, including sylvic acid, 

 which are produced by oxidation of hydrocarbons of the formula 

 Cgn Hgn- It may be extracted by exhausting the dried bark with 

 boilinc^ water, drying it again, and then treatiuQ- it with boilinsj 

 alcohol. The solution on cooling deposits the betulin, which is 

 pressed, dried and re-crystallised from ether. 



Another process for obtaining it pure has been descril:>ed as 

 follows;j: : — The outer bark of the White Birch, previously boiled 

 with water and dried, is boiled for 3 or 4 hours with 20 times its 

 weight of 90 per cent, alcohol in a vessel provided with an 

 inverted condenser : tlie extract is strained while hot, and at once 



* Bericht, April, 1891. 



t Journ. f. Prakt. Clieni., vii., p. 54 ; and xvi., p. 161. 



X LieLig's Annalen, clxxxii, p. 368. 



