26 
Indian Forest Records. 
[Vol. VI 
well made that the loss of the solvent in a temperate climate is said 
not to exceed 0-5—1 per cent., and that even in India it is not expected 
to exceed 5 per cent, per 100 parts of the raw material : one firm 
working in India claims to work at a 2 per cent, loss onlv. 
To keep down to this figure, however, condensation must be care¬ 
fully attended to, and it is not advisable to attempt condensation with 
water at a higher temperature than 80°Fah., unless an unlimited supply 
of water is available, but even then the recovery of the solvent will take 
such an inordinate length of time that it is by no means certain that, 
under Indian conditions, it would not be better to take the loss at say 
-'5 per cent, instead of 2 per cent. 
The Boswellia oleo-resin is soluble in all of the following solvents 
(1) Alcohol (90 per cent., boiling point 78°C.) 
(2) Ether anhydrous (boiling point 35°C.). 
(3) Carbon-tetrachloride (boiling point 76°C.). 
(4) Chloroform (boiling point 62°C.). 
(5) Trichloroethylene (boiling, point 88°C.). 
(6) Petroleum ether (boiling point up to 60°C.). 
(7) Petroleum benzine (boiling point 80°-110°C.). 
(8) Acetone (boiling point 56°C.). 
(9) Coal-Tar Naphtha (boiling point up to 110°C.). 
(10) Benzol (boiling point 80°C.). 
(11) Turpentine (boiling point 155°-160°C.)* 
Out of these Nos. (2), (3), (4), (6) and (10) are too costly to be con¬ 
sidered for extraction on a commercial scale in this country. No. (5) 
is already used extensively for the extraction of oils, it is not inflam¬ 
mable and is recoverable to the extent of 98 per cent, in cold climates, 
like that of England and up to 95 per cen£. in hot climates. Trichloro- 
ethylene appears to be an ideal solvent and its use is recommended 
for the extraction of Boswellia oleo-resin. Pre-war London prices were 
£45 per ton. Taking £46 per ton as the price of the solvent imported 
from England and delivered at the factory, it works out to annas 4-9 
per pound or about Rs. 1-4 to extract one maund of resin, taking a 
maximum loss of 5 per cent, of the solvent during its recovery. 
Acetone and alcohol are good solvents, but as they are miscible in 
water, their recovery is seriously affected by the admission of steam 
which is necessary for the full recovery of the solvent and, for this reason, 
the solvent chosen should be very volatile and immiscible with water. 
Alcohol dissolves the tannin and other colouring matter out of the woody 
chips and bark pieces contained in the crude material, which colours 
the residual gum light brown. The resin produced by alcoholic extrac¬ 
tion is also a shade darker than that produced by petroleum benzine. 
[ 328 ] 
