7 
Part I.] Puran Singh: Turpentine Oil and Indian Rosin. 
Influence of air on turpentine oil .—Turpentine oil when allowed 
to stand in open vessels suiters a rapid change, especially if it 
contains water. The oil gradually becomes rancid and the specific 
gravity, boiling point, and solubility in 90 per cent, alcohol 
increase; the originally neutral oil becomes acid and resinifi.es. 
All these changes are due to a slow oxidation caused by the atmo¬ 
spheric oxygen. Turpentine oil when oxidized in the presence of 
moisture has been show*n to contain hydrogen peroxide, which 
makes it an active oxygen carrier, that is, turpentine, whether dry 
or moist, when charged with oxygen, has the capacity to convey 
oxygen to such substances that are not directly oxidizable with the 
atmospheric oxygen. 
Composition .—Turpentine oil is a mixture of hydrocarbons called 
terpenes of the general fomula C 10 H 16 . Though these hydro¬ 
carbons are identical in their chemical composition, they have yet 
distinctive physical properties. The chief constituent of the tur¬ 
pentine oil is pinene (b. p. 155°—156° C.), which is a very labile 
terpene. In production of turpentine oil, part of the pinene 
undergoes decomposition, and the decomposition products become 
mixed up with the oil. As already stated, the oil contains traces 
of formic, acetic and other resin acids which at higher tempera¬ 
tures react on pinene producing dipentene and other polymeric 
terpenes. 
When turpentine oil is subjected to fractional distillation, those 
of the constituent terpenes that have a low^er boiling point than the 
others pass over first, while those having a high boiling point come 
over next. Thus the oil can be separated into various fractions, 
which are mixtures in varying proportions of two or more different 
constituent terpenes. It may be remarked here that though the 
observation of the amounts of the different fractions of the same 
oil by different observers seldom agree, as they all depend on the 
form of the distilling flask, the rapidity of distillation and the 
barometric pressure, yet, for all practical purposes, the fractional 
distillation of different samples gives a very good idea of the 
quality of the oil. The greater the amounf of the fraction (passing 
over below 165° C.), the better is the quality of the oil. A good oil 
in general passes over almost entirely below 180° C., and the greater 
the amount of the fractions passing over above 180° C. inferior 
will be the quality of the oil. 
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