608 TEREBINTHINA VULGARIS. 



different, so far as we can judge from the experiments of Duverno}' 

 (1865) and of one of ourselves (F.) 



Abietic acid, as well as the unaltered coniferous resins, deviate the 

 ray of polarized light, whereas American colophony, dissolved in 

 acetone, is devoid of optical power. 



Commerce — The supplies of turpentine are chiefly derived from the 

 United States, but the trade has undergone a gi-eat change, as shown by 

 the following figures, which represent the quantities imported in the 

 several years : — 



1869 1870 1871 1872 



60,468 cwt. 51,257 cwt. 2,231 cwt. 1,000 cwt. 



This greatly diminished importation of the crude article is partially ex- 

 plained by a larger importation of Oil of Turpentine and Rosin ; but the 

 increase is by no means sufficient to account for the vast diminution 

 indicated by the above figures. The quantities of these latter articles 

 imported into the United Kingdom during the year 1872 were as 

 follows : — Oil of Turpentine, 220,292 cwt., value £470,085, six-sevenths 

 being furnished by the United States of America and the remainder 

 chiefly by France. Rosin, 919,494 cwt., value £492,246 ; of this 

 quantity, the United States supplied nine-tenths, and France the 

 larger part of the remainder.^ 



Uses — Turpentine, Common Frankincense and Colophony are 

 ingredients of certain plasters and ointments. Oil of turpentine is 

 occasionally administered internally as a vermifuge or diuretic, and 

 applied externally as a stimulant. But these substances are immea- 

 surably less important in medicine than in the arts. 



Thus Americanum vel vulgare. 



This substance, known among druggists as Common Frankincense 

 or Gum Thus, is the resin which, as explained at p. 605, concretes upon 

 the stems of the pines in the American turpentine orchards, and is 

 there called Scrape. It corresponds to the Galipot or Barras of the 

 French, which in old times supplied its place. 



It is a semi-opaque, softish resin, of a pale yellow colour, smelling 

 of turpentine ; it is generally mixed with pine leaves, bits of wood and 

 other impurities, so that it requires straining before it is used. B}- 

 keeping, it becomes dry and brittle, of deeper colour and milder odour. 

 Under the microscope, it exhibits a crystalline structure due to A hietic 

 Acid, of which it chiefly consists. It is imported from America in 

 barrels, but in insignificant quantities and only for the druggist's use. 

 Sometimes, however, it is distilled as common turpentine. 



Dry pine resin, of which Common Frankincense is the type, evolves 

 when heated an agreeable smell ; hence in ancient times it was com- 

 monly used in English churches in place of the more costly olibanum. 

 At present it is scarcely employed except in a few plasters. 



1 Annual Statement of the Trade of the U.K. for 1872. pp. 53. 56. 60. 210. 



