80 Indian Forest Records. [Vol. IV. 
colour and transparency to that obtained by either water distilla¬ 
tion or steam distillation. 
Both for the quality of the oil and the rosin, it may appro¬ 
priately be pointed out here that whatever process be adopted, 
it is essential that the still must be “ cut ” and the distillation be 
not allowed to proceed to its utmost limit. 
Experiments on the Reduction of Colour of Indian Rosin. 
Besides the trials made at Bhowali to improve the colour of 
rosin by adopting spirit distillation or by carrying on water dis¬ 
tillation at a low temperature, the writer made a series of compara¬ 
tive experiments in the Laboratory to reduce the colour of the 
Indian rosin with results given below. The observations as to the 
colour were made on slabs of equal size prepared from the same 
quality of rosin by different treatments. The rosin treated was of 
dark deep-yellow and light-yellow colours. 
Action of simple heating .—First of all it was seen that repeated 
melting has an injurious effect on the colour of rosin. Pale yellow 
American rosin when melted only once changed into reddish yellow, 
and the colour deepened still further on repeated meltings. This 
may be attributed to either slight charring or aerial oxidation under 
the influence of a high temperature. 
Action of steaming .—Steaming has no good effect on the colour 
of rosin. It darkens it and makes it opaque due to the presence of 
water. 
Action of sulphur dioxide and chlorine .—Both of these bleach¬ 
ing agents have destructive effect on rosin as they darken it to 
some extent. 
Action of copper , lead and iron in metallic form .—When a pale 
coloured variety of rosin is heated strongly to perfect fusion with 
metallic copper, lead or iron, its shade becomes darker. After re¬ 
peated observations it was found that the contact of these metals 
with strongly heated rosin injuriously affects its colouration. 
The stills in the turpentine factories are generally made of copper 
and hence some amount of discolouration unavoidably takes place 
in the stills. 
C 80 ] 
