64 BULLETIN 1003, U. S. DEPARTMENT OF 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 | 
FO GSO .86090.8700 
ISIS 
.s 
iS 
s 8 
SS 
XN 
Os 
ee 
SH 
x 
% Q 
IN) 
LS) 
S 
GA 70 
FLP CLNT DISTILLLO 
Fie. 8. Pegi gravity of distillate. 
GO GO 100 
boiling point, specific oravity, ta refractive index rise rapidly, | 
showing that the composition of the distillate is undergoing a further — 
marked change. aA 
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 | 
