OXIDATION OF MANILA COPAL BY THE AIR. 225 



prevailing here and the more intense sunlight of the Tropics would cause 

 more rapid oxidation. 



The increase in the Koettstorfer number of a resin which has been exposed to 

 the air also points to the rearrangement of peroxides to lactones. A similar 

 phenomenon perhaps occurs in the ease of linseed oil. Lewkowitsch - 3 gives the 

 saponification number of a sample of blown linseed oil as 287, or about 100 

 units higher than for ordinary raw oil. 



Certain hydroxy-acids in the aromatic series give Koettstorfer numbers which 

 are considerably higher than the values calculated for the carboxyl-group alone. 24 

 This fact might be cited to show that the increase in the Koettstorfer numbers 

 of samples of oxidized copal is due to the formation of hydroxy-acids, which 

 might also form . lactones. However, such an explanation would be difficult to 

 apply to turpentinp. 



Since the oxidation by the air of these widely different substances is 

 evidently due to their unsaturated character, is accompanied by the 

 formation of organic peroxides, and gives rise to reaction products the 

 formation of which is readily explained by the breaking down of the 

 peroxides, it is evident that the only explanation which will suit all of 

 these cases is that the changes which take place during autoxidation 

 depend on the formation of organic peroxides. 



OTHER PRODUCTS OF THE OXIDATION OE MANILA COPAL BY THE AIR. 



Formic acid has repeatedly been found as a product of the atmospheric 

 oxidation of linseed oil and turpentine. It is also formed during the 

 autoxidation of Manila copal. 



A freshly powdered sample of the resin possesses a pleasant aromatic smell, 

 but on standing for a few days in a loosely stoppered bottle acquires a sharp 

 irritating odor. A small evaporating dish containing a dilute solution of hydrox- 

 ide was placed in a jar containing about 300 grams of powdered resin and 

 allowed to stand for three weeks. The solution was then diluted, acidified, with 

 sulphuric acid, and distilled until one-half of it had passed over. This was 

 neutralized by ammonia, concentrated to about 2 cubic centimeters, and the 

 presence of formic acid shown by the ferric chloride test. Its presence was also 

 shown by dissolving 200 grams of powdered resin in cold, diluted alkali, precip- 

 itating the resin acids and filtering. The filtrate was then neutralized and 

 concentrated, acidified with phosphoric acid, and distilled until about one-half had 

 passed over. The distillate was treated as before and a positive test for formic 

 acid was obtained. 



Formaldehyde is also a product of the autoxidation of Manila copal. 



An open dish containing 10 cubic centimeters of water was placed in a jar 

 containing 200 grams of powdered resin and allowed to stand for one week. At 

 the end of this time the water was strongly acid, and three drops were sufficient 

 to give an unmistakable test for formaldehyde when tested by the well-known 

 color reaction with milk and sulphuric acid containing a trace of ferric chloride 

 and by the reaction between hexamethylene tetramine and bromine water. 



23 Analyst (1902), 27, 140. 



^Fahrion, Ztschr. f. ang. Chem. (1901), 14, 1225. 



