CHEMISTRY IN THE TELEPHONE INDUSTRY 



619 



the soils and the underground waters and atmosphere often play an 

 important role in determining the kind and extent of corrosion by stray 

 current. 



Other occasional cases of electrochemical corrosion have been en- 

 countered in which stray current, though present, does not arise from 

 trolley-line power houses. In one large city it was found that a battery 

 covering a square mile or more of area had been inadvertently created, 

 such that it affected a large part of the cable system in the center of the 

 city. The cinder fills underlying the duct runs in this area contained 

 enough carbon to serve as one electrode, while the iron-pipe systems 

 supplying gas and water to the city furnished the other electrode. The 



Fig. 6 — Experimental metallurgical shop. 



moist soil afforded a conducting path for a galvanic current that 

 wrought a widespread damage to telephone cables in the area. 



In another and much larger area widespread injury to cables came 

 about through the presence of traces of acetic acid in the air in wooden 

 duct systems. The source of this acid was the wood itself, which hap- 

 pened to be of a rather highly acid variety. The natural acidity of the 

 wood was further increased by the somewhat drastic process of heating 



