16 WOOD TUEPENTINES. 



and index of refraction 1.4714 and about 5 per cent of some other 

 material, fr, with values of all properties considerably higher (say, 

 specific gravity 0.95, index 1.489). The gradual increase in the 

 values of all the physical properties from the first fraction up to 95 

 per cent might be thought to be due to a gradually increasing pro- 

 portion of this high-boiling and heavy material in the distillate (as 

 was the case in the boiling-point curves of fig. 3) ; but this inter- 

 pretation is shown to be incorrect by a procedure to be described 

 a procedure which was carried through for an entirely different pur- 

 pose (see p. 25). 



Figure 13 gives the result of a distillation of a part of the tur- 

 pentine used in figure 2, which had been redistilled several times in 

 order to remove the high-boiling and heavy material originally 

 present. The curves show that this heavy material, >, has been en- 

 tirely removed, and yet the values for all the physical properties in- 

 creased to some extent as the distillation progressed, which indi- 

 cated that the distillate was not a pure substance. Evidently, then, 

 the gradual increase of these values in figure 2 was not due to the 

 presence of l> in the first 95 per cent of the distillate, but instead there 

 must have been present another substance, c, with physical properties 

 only slightly higher than those of #, the boiling points of a and c 

 being so close together that the substances are very incompletely 

 separated by distillation. 



This interpretation agrees with the results of recent investigations 

 of the chemical constituents usually present in turpentine. Accord- 

 ing to Semmler, 1 there may be present in American turpentine be- 

 sides pinene 2 two other terpenes, camphene and nopinene 3 . ' The 

 physical properties of these two terpenes have not been accurately 

 determined, but it is sufficient to know that they are all higher than 

 those of pinene. The first 95 per cent of the distillate from this tur- 

 pentine was probably composed of a mixture of pinene with either 

 camphene or nopinene, or both, and the last 5 per cent was made up 

 of materials with much higher physical properties, probably oxida- 

 tion products of the terpenes. 



In the distillation of turpentine by this method the separation be- 

 tween the terpenes and the high-boiling nonterpenes is sufficiently 

 complete, so that the physical properties of the first fractions are not 

 appreciably influenced by the presence of materials with boiling 

 points of from 30 to 35 higher. The mixture of the terpenes 

 pinene, camphene, and nopinene is, however, not sufficiently well 

 separated to make it possible to estimate the proportions of the dif- 



1 " Die Aetherische Oele," Vol. II, pp. 55 and 274. 



2 Boiling point, 155-156 C. ; specific gravity, 0.863; index of refraction, 1,4678. 

 8 The physical properties of both about the same at the following values : Boiling point, 

 160 to 165 ; specific gravity, 0.874 ; index of refraction, 1.4724. 



