40 
Journal of the Mitchell Society. 
[ May 
composed? This question has interested chemists for 
many years. The literature of the subject is very exten- 
sive and the views held at various times were and even 
now are widely different. By Maly and Fliickiger rosin was 
considered the anhydride of abietic acid. Henriques con- 
tended for the presence of lactonic acids, Benedict for free 
acids and ethereal salts, Fahrion for sylvic acid, while 
Tschirch has recently separated from American rosin three 
isomeric acids a, (3 and y abietic acids, and considers that all 
other workers in this field have been dealing- with impure 
products. The controversy on this subject between Tschirch 
and Fahrion is not yet ended. Tschirch can not decide 
between C I9 H 28 O a and C 20 H 30 0 2 as the correct formula for 
abietic acid. Nor has it been determined with any certainty 
whether the oxygen atoms of this acid are present in the 
form of hydroxyl or carboxyl groups. It is possible that 
some of these differences may be due to the fact that many of 
the specimens used for investigations are so called “Amer- 
ican Rosins,” without taking into account the fact that much 
of this rosin is derived from at least two different species of 
pines, Pinus Palustris and Pinus Heterophylla. 
Rosin varies in color from a pale yellow to a very deep red, 
the price of the rosin decreasing with increasing color. In 
France the better grades of rosin are placed in shallow trays 
and exposed for three or four months to the bleaching action 
of sunlight. Almost colorless grades are thereby obtained. 
This practice is carried on by one firm in this country. But 
sun-bleaching is not effective with the darker rosins. The 
great difference in price between the low and high grades 
has led to many efforts to devise chemical methods for bleach- 
ing rosin. A number of patents have been issued on the 
subject, but so far as I know none of these have proved 
commercially profitable. Here is a live problem for the 
chemist, the correct solution of which is certain to bring rich 
returns. 
For many years the commercial demand for rosin was very 
