64 



BULLETIN 1003, U. S. DEPARTMENT OK AGRICULTURE. 



index 1.4730, each at 20 C., boiling point 178 C.), dipentene being 

 known to be a constitutent of wood turpentine. A materially higher 

 temperature than the boiling point of betapinene at which, even from 

 the beginning, the turpentine distils, points further to the presence 

 of appreciable amounts of dipentene, the greater portion of the 

 turpentine distilling at a temperature intermediate between that of 

 beta-pinene and dipentene. Above 80 per cent of total distillate the 



60 TO #0 00 /Off 



FIG. 8. Specific gravity of distillate. 



boiling point, specific gravity, and refractive index rise rapidly, 

 showing that the. composition of the distillate is undergoing a further 

 marked change. 



The principal constituents of turpentine, collectively spoken of 

 as terpenes, are a closely-related series of organic compounds pos- 

 sessing such a close similarity in chemical and physical properties 

 that precise knowledge concerning their quantitative estimation has 



