so 
Indian Forest Records. 
[Vol. VI 
brown colour in the sun. This disadvantage is, to a certain extent, 
counteracted by the use of ferric oxide, as none of the specimens of var¬ 
nished woods, which were varnished with thitsi containing ferric oxide, 
were, to any very noticeable degree, affected in this way, although the 
test was a severe one. 
The conclusions, therefore, which have been arrived at in the course 
of these investigations are :— 
( i ) The results, given by Mr. Puran Singh are confirmed. 
(ii) The use of BoswelUa serrata oil or oil of turpentine in no 
way improves the drying capacity of the crude varnish : 
the addition of these oils only makes the substance thinner 
and more workable. 
(in) The addition of ferric oxide greatly increases the drying 
capacity of the varnish, apparently removes its poisonous 
properties, and retards the change in colour of the varnished 
articles when placed for any length of time in the sun. 
It must, however, be remembered that the addition of 
this drying agent tends to dull the gloss of the varnished 
articles. 
(iv) The drying action of ferric oxide is probably due to oxidiza¬ 
tion, but it has been suggested that the action of the 
urushic acid of the varnish on the iron salt causes the 
latter to split up into a ferro-urushate salt. 
(v) That, owing to the dulling action of the ferric oxide, it should 
be used only in small quantities when a high class finish 
is desired. 
(ft) That the use of ferric oxide, as a drying agent in the initial 
stages of the lacquer process, would simplify the drying 
process and accelerate the production of the finished article. 
(mi) That, owing to the restricted use to which a thick black 
varnish can be put, it seems unlikely that it will ever find 
its way on to the market in any considerable quantities 
except as a lacquer varnish, but there seems no reason why 
it should not compete favourably with the lacquer varnish 
now exported from China and largely used in Europe. 
No experiments were undertaken to show the effect of strong alkalies 
or of acid on thitsi adulterated with ferric oxide. 
9. Yield per Tree and Cost of Extraction. 
The size and appearance of a tree is often misleading as to the amount 
of oleo-resin it will produce, as a large tree may produce very little 
E ne 3 
