INFLUENCE OF MOISTURE UPON INSULATORS 241 



involve only water condensed upon the surfaces of the elements of 

 structure in such a way that the thickness of the film varies regularly 

 from point to point through the material. Accumulation of water 

 at thick points would have little electrical effect, while that in thin 

 portions would be very significant. An alternative regular mode of 

 distribution would involve water in part dispersed in solution or 

 chemical combination within the units of structure of the material 

 and in part in fairly uniform thin films on their surfaces, in which 

 case the latter would have the major electrical consequence. While 

 such a regular form of distribution seems preferable, it is perhaps 

 not the only way of accounting for the electrical properties observed. 

 The curves as shown in Fig. 4 for both cotton and silk are straight 

 lines within the experimental error but the assumption is not justified 

 that they can be projected as straight lines to zero humidity. At the 

 lower ranges of humidity the resistance of silk is so high as to exceed 

 the limits of our present technique of measurement. Over some 

 range below 40 per cent relative humidity, it may well be that the 

 sensitivity of the animal fibers to increments of moisture is less than 

 that of the cellulose fibers. If so, the break in the curve would have 

 great interest in connection with determining the mode of water 

 distribution and in turn the colloidal structure of the materials in 

 question. It is hoped that an extension of the study in this direction 

 will be possible in the future. 



Summary 



Attention is called to the practical importance of water in all 

 insulators and especially to the extreme electrical sensitivity to 

 moisture of textiles as a class. 



Significant amounts of electrolytic impurities occur in many in- 

 sulators. 



In textiles in the presence of moisture such impurities are responsible 

 for very conspicuous features of electrical behavior. Data are given 

 showing their effect on the insulation resistance of cotton and silk. 



The insulation resistance of textile fibers in moist air rises greatly 

 with duration of d.c. voltage, accompanied by many evidences of 

 electrolysis of aqueous solutions of impurities in the textile. 



The instantaneous insulation resistance of fibers decreases with 

 increase of the measuring voltage as previously shown by Evershed. 

 However, this fact does not necessarily support his idea of kinetic 

 redistribution of water in textiles, as this behavior is also compatible 

 with the nature of electrolytic conduction. 



Electrolytic impurities may be washed out of textiles and sub- 



