256 BELL SYSTEM TECHNICAL JOURNAL 



such materials as fabric base insulating tapes, varnished linens and 

 cambrics, electromagnet coil winding insulation, all being sensitive 

 electrically to moisture, should be benefited to a substantial degree by 

 purification of the fibrous components. 



Therefore, while there is still much to be learned about the behavior 

 of silk and cotton with respect to their electrical characteristics under 

 various treatments and conditions, the study has progressed to the 

 point where the following statements can be made. 



1. The removal of water soluble salts which are present in both silk 

 and cotton not only results in a very decided improvement in their 

 insulating properties, but reduces the sensitivity to change of the a.c. 

 characteristics with changes in atmospheric moisture conditions. 



2. The improvement which can be realized is great enough to permit 

 the substitution of washed cotton for silk where ordinary commercial 

 silk has been found to give satisfactory results. 



3. The use of purified textiles in cables carrying continuous d.c. 

 potential will reduce electrolysis and consequently prolong the useful 

 life of such cables about in proportion to the extent to which the 

 purification process is carried. 



In presenting the foregoing discussion, the authors wish to ac- 

 knowledge their indebtedness to engineers of the Western Electric 

 Company whose work in cooperation with silk suppliers has been 

 largely responsible for the development of commercial methods of 

 purifying insulating silk. Acknowledgment must also be made of 

 the importance of the fundamental and research work which underlies 

 the engineering result briefly described by this paper. 



