62 SMITH— CATHODIC PRECIPITATION OF CARBON [January 4, 



heating and gave carbon dioxide when acted upon with a chromic 

 acid mixture. In later experiments, Coehn was able to determine, 

 in the electrolytic way, the equivalent of carbon and found it to be 3. 



Turning to our observations with tartaric and citric acid, it must 

 be that these are broken down at the anode, during electrolysis ; 

 that the carbon thus liberated from combination in these acids 

 enters aqueous solution as a hydrate of which the carbon is cation, 

 and this, under influence of the current, passes in its ionic form to 

 the cathode just as a metal, in some salt, does under similar in- 

 fluence. When, therefore, iron is deposited from a citrate or tar- 

 trate electrolyte, the carbon ions wander with the iron ions to the 

 cathode, and there an alloy of iron and carbon appears. This alloy, 

 on treatment with dilute sulphuric acid, generates hydrocarbons. 

 Very little, if any, of the carbon deposited with iron is graphitic. 

 It is chemically combined. Just as zinc and copper, from certain 

 electrolytes, separate as brass, so do the carbon and iron separate 

 as an alloy from the electrolytes which have been under discussion. 



The conclusions warranted from the experiments here noticed 

 and many others like them are : 



1. Carbon is deposited on the cathode from solutions containing 

 tartaric, citric, lactic and benzoic acids. This is particularly the 

 case if a stationary anode be used along with high current density. 



2. From solutions like those in i, where high current density 

 is employed, platinum will dissolve from the anode and be precipi- 

 tated in part upon the cathode. 



University of Pennsylvania. 



Stated Meeting January 18, 190'j. 



President Smith in the Chair. 



The following papers were read : 



** Pennsylvania at the Jamestown Exposition, illustrated by the 

 Lincoln Migration," by Prof. Marion D. Learned, which was dis- 

 cussed by Mr. Richard Wood, Prof. Cheyney and Prof. Leslie W. 

 Miller. 



'' Reproduction, Animal Life Cycles and the Biological Unit," by 

 Prof. Thomas H. Montgomery. 



