28 



PHILIPPINE RESINS, GUMS, AND OILS 



Table 3. — Per cent of substance dissolved from 10 grams of resin by 100 

 cubic centimeters of solvent. 



Solvent. 



Ethyl alcohol 

 Amyl alcohol 



Ether 



Ligroin 



Benzene 



Turpentine . 



Per cent. 



Temper- 

 ature 



used to 

 expel 



solvent. 



°C 



130 



150-155 



120 



130 



135-140 



170- 175 



OXIDATION OF MANILA COPAL 



The absorption of oxygen from the air appears to be a prop- 

 erty common to all complex resin acids. Brooks * investigated 

 the oxidation of Manila copal by air and summarized his re- 

 sults as follows: 



1. Manila copal rapidly absorbs oxygen from the air. The oxidation 

 is accompanied by the formation of organic peroxides, an increase in the 

 Koettstorfer number, and evolution of small quantities of carbon dioxide, 

 formaldehyde, formic acid, and hydrogen peroxide. 



2. The resin acids of Manila copal, when separated from the terpenes 

 occurring in the natural resin, undergo oxidation by the air. 



3. The evolution of carbon dioxide from Manila copal and colophony is 

 probably due to the formation of organic peroxides and their subsequent 

 decomposition. 



4. The increase in the Koettstorfer number obtained by prolonged di- 

 gestion w^ith alcoholic potassium hydroxide is not due to oxidation during 

 the course of the experiment, but is probably caused, at least in part, by 

 the breaking dow^n of lactones and organic peroxides. Samples which have 

 been exposed to the air give up carbon dioxide and formic acid to the 

 alkaline solution in the Koettstorfer determination and cause the recovered 

 resin to show lower Koettstorfer numbers than the initial values. 



5. Formaldehyde has heretofore not been noted among the products of 

 the oxidation of organic substances by the air. I have found it among 

 the products of the atmospheric oxidation of Manila copal. 



6. The oxidation of Manila copal by the air is accelerated by sunlight. 



Ingle t examined Manila copal to ascertain the effect of ex- 

 posing it to the air. The material was finely ground and ex- 



* Brooks, B. T., Oxidation of Manila copal by the air. Philippine Journal 

 of Science, Section A, Volume 5 (1910), page 219. 



t Ingle, H., Some notes on gum resins. Journal of the Society of 

 Chemical Industry, Volume 31 (1912), page 272. 



