Part I.] Puran Singh : Turpentine Oil and Indian Rosin. 81 
Action of metallic tin .—Of all tlie common metals it lias come 
under tlie observation of tbe writer, that contact of molten resins 
with metallic tin exerts a beneficial influence on the colour of diff¬ 
erent resins. It was seen that by keeping melted rosin in contact 
with granulated tin there was a distinct improvement in its colour, 
particularly the dark coloured variety was reduced to half of its 
original depth of colour. 
Action of albumen. —Albumen in the shape of animal blood 
clarifies rosin owing to coagulation consequent on the heat of the 
melted rosin and by absorbing in itself the suspended impurities- It 
improves the colour of rosin appreciably and makes it perfectly 
transparent, but the process is too costly to be employed on a com¬ 
mercial scale. 
Action of salt .—Boiling rosin with salt solution as done by soap- 
makers to reduce its colour is a long and tedious operation and not 
entirely effective. 
Action of acetic acid. —The addition of a small quantity of ace¬ 
tic acid to the molten rosin makes the latter transparent and bright. 
But the addition of a free acid cannot be recommended, as its pre¬ 
sence is objectionable. 
Action of potassium chlorate and nitre. —Oxidising agents like 
potassium chlorate and nitre in small quantities impart a reddish 
tinge to the pale straw varieties of colophony, but in excess, they 
have an injurious effect on the colour and composition of rosin. 
Pale rosin heated with them for a long time changes colour to a deep 
dark red. 
Action of carbon dioxide, hydrogen and nitric oxide. —A passing 
reference may be made here to a recommendation made by 
certain authors to bleach rosin in small quantities by introducing 
a gentle current of carbon dioxide, hydrogen or nitric oxide gas 
into molten rosin for some time- The efficacy or otherwise of 
these agents has not been tried by the writer as their application 
on a commercial scale is out of the question. 
Action of sunlight .—A thin layer of yellow rosin was exposed 
to sunlight on a glass surface for ten days with the result that 
it was entirely bleached water white. It is questionable wTiether 
sunlight bleaching of rosin in India will be commercially successful 
on account of the length of the process. 
[ 81 ] 
G 
