812 THE BELL SYSTEM TECHNICAL JOUKNAL, MAY 1957 



several differences in the conditions necessary for formation. The carbon 

 is produced on a noble metal but not on a base metal (in air) ; brown 

 deposit, on the other hand, has been formed on vanadium, molybdenum 

 and tantalum, but it has never been produced on silver and only spar- 

 ingly on gold.'-" The failure of electrodes of silver and of gold to form 

 brown deposit has been associated with the high thermal conductivities 

 of these metals, with the idea in mind that polymerization of organic 

 molecules to brown deposit requires frictional heat. Whether this is true 

 has not been established. 



Both brown deposit and the carbon of activation can be formed from 

 any of a great variety of unsaturated ring compounds. Various unsatu- 

 rated aliphatic compounds which have been tested, and some saturated 

 aliphatic compounds (for example, pentane), can be made to produce 

 brown deposit to a limited extent, but activation has never been attained 

 with any aliphatic compound. It seems probable that some activating 

 carbon is produced from these compounds but the burning off in the 

 arc makes activation impossible. 



ACKNOWLEDGMENT 



The work reported here is the joint effort of a number of persons whose 

 contributions are acknowledged in the appropriate places. The authors 

 coordinated the investigation and are responsible for its general plan. 

 The authors are indebted furthermore to R. H. Gumley for many helpful 

 criticisms. 



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