ABSTRACTS OF TECIISICAL ARTICLES 321 



edge used in optics is applied to explain the reduction. Coexisting 

 phenomena are mentioned. 



Oxidation Studies of Rubber, Gutta-Percha, and Balata Hydrocarbons.'' 

 A. R. Kemp, W. S. Bishop, and P. A. Lasselle. The oxidation 

 mechanism of rubber and gutta-percha hydrocarbons has been studied. 

 Rubber hydrocarbon in sheet form oxidizes more slowly and less 

 completely than precipitated gutta-percha, which is believed to be due 

 to the smaller surface exposure of the former material. Gutta-percha 

 hydrocarbon in finely divided form oxidizes to a fairly definite degree 

 in oxygen at room temperature, corresponding to a weight increase of 

 about 38 per cent. The length of the autocatalytic induction periods 

 for rubber and gutta-percha varies over a wide range and is shortened 

 by heating the hydrocarbon in high vacuum before oxidation and by 

 exposure to light. 



The rate of oxidation of gutta-percha in air, as compared with oxy- 

 gen, is reduced in proportion to the oxygen concentration, and the 

 induction period is correspondingly increased. 



Carbon dioxide, water, formic acid, and formaldehyde are identified 

 in the volatile oxidation products, and their relative amounts deter- 

 mined. Six to eight per cent of the hydrocarbons are converted to 

 volatile oxidation products. The percentage unsaturation of both 

 rubber and gutta-percha hydrocarbons is reduced in proportion to 

 oxygen absorbed. The ratio of hydrogen to carbon decreases as a 

 result of oxidation. 



The solid oxidized products are of such a nature that they cannot 

 be resolved into crystalline materials. They are amorphous acid 

 substances, free from aldehyde and ketone groups. They contain a 

 small amount of peroxides; and the acidity, saponification value, and 

 other properties indicate that most of the oxygen is combined in the 

 form of hydroxyl, carboxyl, and lactonic groups. The mechanism of 

 oxidation of rubber and gutta-percha appears to be the same, and the 

 possibility of a chain mechanism to explain the facts is discussed. 



Modern Developments in Precision Clocks.^ A. L. LooMis and W. A. 

 Marrison. a discussion of precision clock requirements is given in 

 terms of the general equations of motion of an oscillator and extended 

 specifically to the gravity pendulum and the crystal oscillator types. 



One of the largest sources of error in pendulum clocks is due to 



'' Jnd. and Engg. Chem., December, 1931. 



8 Presented at A. I. E. E. Midwinter Convention, Jan. 25-29, 1932, New York, 

 N. Y., as a part of the Symposium on Time and Time Ser\-ices. To be published in 

 full as Monograph B-656, Bell Telephone System Technical Publications, and available 

 upon request to Bell Telephone Laboratories, New York, N. Y. 



