34 Indian Forest Records. [Vol. IV. 
not come in contact with the air. The presence of resinous im¬ 
purities and any considerable contact with the air will alter the 
fractions of the oil. 
(7) Before the oil is sent to the market it should be properly 
examined. A good rectified Indian turpentine oil should answer the 
following tests: — 
(i) Sp. gr. at 20° C. 0-860—0-864 
( ii ) Parts of 90 per cent, alcohol required by one part 
of turpentine to effect solution .... 7—7’2 
(Hi) 10 c.c. of the oil put on clean glass surface should completely evaporate in 
24 hours in the shade and in 8—9 hours in the sun, leaving no residue or at 
the most a thin sticky film, due to oxidation. 
(iv) When applied with a brush on a clean glass surface 6" x 4" and exposed to 
sun, it should dry in about 15 minutes, leaving no greasy residue nor a 
sticky surface. This test is very simple, but care must be taken that the 
finger used to judge the surface is perfectly dry and free from resinous 
or greasy feel. 
Some merchants prefer to dip a piece of clean white paper in turpentine 
oil and see the nature of the stain left by it. A good turpentine oil 
should leave no trace of any oily stain. It should dry clean in a few 
minutes. 
( v) When shaken with 5 per cent, caustic soda solution, it should give no 
coloured under-layer nor a milky layer. This test is useful in detecting if 
any rosin has distilled over and dissolved in the turpentine. 
( vi ) It should, on fractional distillation, wholly or almost wholly distil over 
under 170° C. at a barometric pressure of 25"—27", in an ordinary 
fractional distillation flask. 
(vii) It is essential that in the distillation of Pinus longifolia resin the dis¬ 
tillation temperature and the temperature of the resin during distillation 
be kept as low as possible. The best method of distillation, therefore, 
will be superheated steam distillation in vacuo with or without the 
addition of a little methylated spirit; a suitable apparatus would be 
some form of the ordinary vacuum still fitted with steam pipes and 
modern types of double-surfaced condensers; at the same time there 
appears to be no reason why the process of simple steam distillation 
with the addition of methylated spirit to the crude resin should not 
answer well. In either case the distillery should have a separate still 
for the recovery of spirit from the distillate. 
Should the above be not easily available spirit distillation carried out on 
the same lines as water distillation will give nearly as satisfactory 
results. But the form of the still should be globular, and the delivery 
pipe should be so placed as to prevent the resinous impurities from 
mechanically passing over into the distillate. 
(viii) In the first distillation of the crude resin, in spite of all precautions taken, 
the admixture of resinous impurities with the oil distilled can scarcely 
be wholly avoided, as it will be evident from the behaviour of oil when 
stored in glass bottles for years, as mentioned in Chapter II, page 13. 
For making oil of a uniformly standard quality, it is recommended that 
the oil should be rectified by redistillation in every case, till most of it 
passes below 167°—170° C. and answers the tests given above. 
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