OXIDATION OF MANILA COPAL BY THE AIR. 



227 



SUMMARY. 



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 

 digestion with 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 down 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. 



