INFLUENCE OF MOISTURE UPON INSULATORS 227 



Important contributions to the knowledge of the quantitative 

 relations between the electrical properties of insulating materials and 

 the moisture which they take up from the air have been made by 

 Evershed,* Curtis,^ Kujirai and Akahari,* Setoh and collaborators,'' 

 and other investigators. But in no published work, so far as we are 

 aware, have data been given showing the quantitative relationships 

 between the electrical properties of textile insulations and the electro- 

 lytic material which they contain. Data of this kind' were obtained 

 in the investigation of textiles mentioned above. Part of these data 

 have been reported elsewhere,^ but the investigation is being continued 

 and a further report will be made when it is completed. It will 

 require much further work to establish in detail the importance of 

 contamination with aqueous solutions of electrolytes for every com- 

 mercial insulating material. However, the presentation of the main 

 thesis as a general one is abundantly justified by our constantly 

 growing experience with cases in which such contamination of a 

 variety of insulating materials has actually been found responsible for 

 poor insulating qualities and for corrosion of metallic conducting or 

 supporting elements in contact with them in electrical systems. This 

 paper is intended to emphasize the importance of moisture and 

 electrolytic material on the behavior of textiles as insulators and to 

 discuss briefly the relation of electrical characteristics to physical 

 structure and chemical constitution, so far as possible with the avail- 

 able facts. 



General Characteristics of Textiles 



It is obvious that the rapidity of response of textiles to atmospheric 

 moisture is due first of all to their fibrousness which permits ready 

 access to the interior of the mass through the large surfaces exposed. 

 By contrast, the relative stability of rubber insulations, for example, 

 is clearly due in part to the smaller ratio of surface to volume. 



Since textiles are composed of fibers, it might seem that the resistance 

 of a thread or the serving on a wire should depend largely on the 

 resistances of the contacts between fibers. Further, the fibers them- 

 selves have superficial irregularities which would suggest that their 

 resistance might vary widely from fiber to fiber of the same material. 

 Table \A shows that single fibers of cotton and silk have a resistance '^ 



* The experimental procedure is described elsewhere.'" 



•« Evershed, Inst, of Elec. Eng. Jl. (London) 52, pp. 51-83, 1914. 



5 Curtis, Bur. of Standards, Sci. Paper No. 234 (1915). 



" Kujirai and Akahari, Sci. Papers, Inst. Phvs. & Cliem. Res. (Tokyo), /, pp. 

 94-124, 1923. 



' Setoh and Toriyama, Sci. Papers Inst. Phys. cf Client. Res. (Tokyo), 3, pp. 

 285-323, 1926. 



