76 
Indian Forest Records. 
[Vol. IT. 
rosin ranges between 1*07 to 1’08 and at times it is as bigb as 1*04 to 
1*1. It is quite insoluble in water. It slowly dissolves in equal 
weights of alcohol or glacial acetic acid and readily so in methyl and 
amyl alcohols, acetone, ether, chloroform, carbon bisulphide, alkalies 
and fixed and volatile oils. It dissolves also in benzene and petro¬ 
leum ether. The alcoholic solution of rosin shows acid reaction. 
The acid number of American rosin varies from 146*01 to 157*24 and 
saponification number from 157*24 to 198*24. Its iodine number 
varies from 120 to 185 when treated with Hubl solution for 18 
hours. 
Its chemical composition has been the subject of various re¬ 
searches with very conflicting results. Generally speaking, rosin 
may be said to consist of about 90 per cent. Abietic acid (C 20 H 32 O 2 ) 
and 4 per cent. Abietic anhydride (C 40 H 58 O 3 ) and 6 per cent, hydro¬ 
carbons or unsaponifiable matter. The composition and constants 
of colophony vary with its origin, nature and mode of preparation. 
Colophony is extensively used in the manufacture of soaps, var¬ 
nish and resinates. It is also used to some extent in pharmacy and 
veterinary practice. As an adulterant, it is in demand for adulterat¬ 
ing shellac, dammar and dragon’s blood. According to Fahrion, 
colophony, as required by the varnish-maker, should be light in 
colour, high in acid number and as low as possible in its ester 
number, unsaponifiable matter and substances insoluble in petro¬ 
leum spirit. 
The shellac manufacturers in India have laid down no such 
constants for rosin required by them, but as far as the writer has 
been able to find out it is pale amber grades of rosin that they re¬ 
quire for light-coloured shellac and reddish-yellow for other varieties. 
The colour of rosin depends on the manner in which the turpen- 
„ ^ , tine distillation is conducted and on the 
A summary or French and 
American methods of rosin temperatures employed therein. It also 
manufacture. varies according to the origin and kind of 
crude resin used, the season of tapping and the degree of care 
taken in the manufacturing processes. In France and America 
great care is taken in classifying the crude resin into different 
grades, according to the season of the year in which the trees are 
tapped and the successive number of annual tappings. It may b$ 
C 76 ] 
