44 THE CHEMISTEY OF ESSENTIAL OILS
odour recalling that of menthene. It is probable that a second hydro-
carbon of the formula C 10 H 18 is also present. The oil itself has the fol-
lowing characters :—
Specific gravity at 22°
Kefractive index 1
Optical rotation.
0-S058
1-4670
+ 3-2°