632. The Philippine Journal of Science oe 
show a gradual increase in the saponification and acid values. 
This would seem to indicate an increase in the amount of oxi- 
dized acids of lower molecular weights. Our results with lum- 
bang are quite similar to those which have been obtained with 
linseed oil. Since the constants of these two oils are very much 
alike and they have a similar composition, it is not surprising 
that they act in a similar manner when oxidized. 
The commercial valuation of an oil suitable for the manufac- 
ture of varnish depends on its drying power. This is deter- 
mined by the amount of oxygen it absorbs and also by the time . 
it requires for drying to an elastic skin. It is well known that 
the oxygen absorption of an oil is closely related to the iodine 
absorption; in fact, as pointed out by Lewkowitsch,”* a rough 
proportionality exists between the quantity of oxygen actually 
absorbed by an oil and the amount calculated by multiplying the 
iodine number by 0.063. A determination of the iodine number 
of an oil which is being oxidized gives us, then, an idea of the 
amount of oxygen absorbed. The results recorded in Table 9 
show a decided, gradual decrease in the iodine numbers, indicat- 
ing the gradual absorption of oxygen. 
When these iodine values are multiplied by the factor 0.063, 
the resulting figures show the absorbed oxygen calculated from 
the iodine value, and from these data the average rate per hour 
of oxygen absorbed in successive intervals can be calculated. 
Our calculated values showed that the rate of oxidation, under 
the conditions of our experiment, increased up to a period of 
thirty-one hours, after which, owing probably to increased vis- 
cosity, the rate decreased. Our results would seem to indicate 
that this oxidation process is an autocatalytic reaction and 
the oxidation products which are formed in the early stage of 
the reaction act as autocatalysts and accelerate the reaction. 
Genthe” obtained similar results in his experiments on the 
drying of linseed oil and was inclined to think that the auto- 
catalyst had the character of a peroxide, though he was not able 
to isolate such compounds. 
The oxidation of lumbang oil for various temperatures and 
intervals of time is now being investigated, and further dis- 
cussion of this point will be reserved for a future contribution. 
* Lewkowitsch, J., Chemical Technology and Analysis of Oils, Fats and 
Waxes 1 (1913) 468. 
* Genthe, A., Zeits. f. angew. Chem. 19 (1906) 2087. 
