334 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



dissolved in an essential oil; the latter is separated from the former usually by distillation with 

 steam. 



There are many varieties of turpentine, corresponding to the different varieties of conifera-, 

 but only three are commercially important, as they are the source of the three principal oils of 

 turpentine. 



(1) The turpentine of Pimts pinaster (syn. P. maritima), collected in the southern departments 

 of France around Bordeaux. From it is obtained the French turpentine, which yields 25 per cent 

 of volatile oil. 



(2) The turpentine from Pinus palustris, P. tceda, P. heterophylla, collected in the southern 

 sea-bordering States from North Carolina to Texas. From them, principally from the first source, 

 is obtained the English or American oil of turpentine, which yields 17 per cent of volatile oil. 

 Formerly the P. rigida was also worked for turpentine in the North Atlantic States, but it is now 

 exhausted. 



(3) The turpentine from Pinus laricio var. austriaca, collected mainly in Austria and Galicia. 

 From it is obtained the German turpentine oil, which yields 32 per cent of volatile oil. 



The Russian oil of turpentine is obtained from Pin-m xilvestris and Pin us Icilebourii, by the 

 direct distillation of the resinous wood, without previously collecting the turpentine. It is said to 

 be identical with the German oil of turpentine, but more variable, as it contains products of 

 destructive distillation, both of wood and rosin. 



The turpentines from the different sources differ from each other (1) in their action upon 

 polarized light, (2) in the relative amounts of volatile oil they yield on distillation with steam, and 

 (3) in the nature of the volatile oils they contain. 



Colophony. The rosin in the different varieties of turpentine is practically the same. It is 

 known as common rosin or colophony. 1 It consists chemically of a mixture of several resin acids 

 and their corresponding anhydrides. The chief constituent is abietic anhydride, C 4 JI t2 O 4 , abietic 

 acid being C 44 H W O^. The crystals that are noticed in crude turpentine are the free abietic acid; 

 on melting the thick turpentine, or on distilling the volatile oil, the acid is changed to the anhy- 

 dride. Colophony is nonvolatile, tasteless, brittle, has a smooth shining fracture, sp. gr. about 

 1.08. It softens at 80 C., and in boiling water melts completely at 135 0. 



The volatile oil. The second principal constituent of turpentines are the volatile oils. The 

 chief ingredient of the three turpentine oils is a hydrocarbon of the same composition, Cu,H l(i ; 

 nevertheless the three oils have distinct hydrocarbons differing from each other in physical if not 

 in chemical properties. The empirical formula of the hydrocarbon is C.oH,,;, and according to the 

 latest researches of Wallach^ it has the following structural formula: 



CJf(CJOt) 1 

 I 



Cff 



CH 



thus being a dihydro : para-cymene, paracyinene being 



1 Colophon, :i city of Iconia, whence rosin was nlitiiiin-d by the Greeks. 

 "Ann. C'hem. (Liebig), 239, 49; Ber. d. Cheni. Ges., 24, 1545. 



