CHEMISTRY IN THE TELEPHONE INDUSTRY 609 



autoclaving the rubber by steam pressure has afforded a simple but 

 effective means of stabilizing the material electrically against the 

 action of water. 



Rubber also finds many uses in aerial insulation, a field which is 

 rather backward in its development as compared with the tire industry. 

 The latter has received an incalculable benefit from the large amount 

 of technical research carried on in the last ten years. To a considerable 

 extent it has been our task to adapt technical information derived from 

 the tire industry to the needs of the telephone. The adoption of such 

 expedients as accelerators and anti-aging compounds has contributed 

 a great improvement in the field of insulation. In fact, the aging of 

 rubber in the case of insulation is obviously even more important 

 than in the case of tires. One scarcely expects automobile tires to 

 last for more than a season or two, but rubber insulation must often 

 be exposed to sun and rain for ten years or more. 



Rubber for wire insulation must offer resistance to cutting of the 

 wire through the insulation under severe load, such as is produced by a 

 deposit of sleet. Our chemists have therefore been called upon to con- 

 tribute to the development of a compression-testing machine for rubber 

 which automatically plots the reduction of thickness of wall under an 

 increasing compressive load. By the use of this testing machine sur- 

 prisingly great variations were discovered and corrected in the material 

 supplied by different manufacturers. 



Other useful tools in the study of rubber have been developed. A 

 method has been devised for the direct determination of rubber hydro- 

 carbon in compounds by means of iodine titration. Direct gasomet- 

 ric measurement of oxygen consumption by rubber and other 

 organic materials is performed with a special apparatus for auto- 

 matically maintaining oxygen pressure constant at one atmosphere. 

 Included in the program are cooperative studies of various accelerated 

 aging tests for rubber, notably the Geer test and that of Bierer and 

 Davis. In these ways we hope we are repaying in part our debt to 

 technologists of the rubber industry, as well as serving our own needs. 



Textiles 



Another general class of insulating materials in which study has been 

 well rewarded is that of textiles. It has now been quite clearly shown 

 that textile libers serve as filaments upon which the moisture of the 

 atmosphere is deposited, and that the electrical characteristics of the 

 textiles are determined largely by the thickness and continuity of these 

 water films and the conductivitv of the solutions formed bv contact 



