526 Dr. C. Ludeking on the Action of the 



and remind one very much of, the dendritic forms of metals 

 that grow out from one pole in electrolysis of metallic solu- 

 tions, and the current in that case seems to act just in the 

 ame way as in the gas. 



Finally, when a slip of stiff writing-paper is placed between 

 the two poles, one does not observe, on passing the discharge, 

 a blackening of the side of the paper turned towards the 

 negative pole, which would certainly be the case were the 

 carbon deposited by projection on the positive pole. 



There is, however, some carbon, in the form of soot that can 

 be easily wiped off, deposited on the negative pole, though 

 only in small amount. This deposit is entirely different from 

 that on the positive pole both in quantity and quality, and I 

 believe it is a true projection-deposit. Consequently the 

 action of the electric discharge on this gas is not simple, but ; 

 as might be inferred, almost a priori, of complex character. 



Firstly, and chiefly, we have an electrolytic decomposition 

 by virtue of which the carbon is deposited in a well-conducting 

 form on the positive pole; and, secondly, we have the dissocia- 

 tion due to the heat of the discharge alone, which in quantity 

 is by far inferior to the former. By the heat of dissociation 

 molecules of carbon are set free and are attracted by both the 

 poles by virtue of their constant static charges. 



Concerning the hydrocarbons examined — olefiant gas, 

 marsh-gas, and coal-gas — there is no noticeable difference, 

 qualitatively at least, in the action of the discharge, so that 

 they need not be separately considered. The deposition of 

 carbon takes place more rapidly in proportion as the gas con- 

 tains a higher percentage of carbon ; thus, under the same 

 conditions in the same length of time, more carbon is deposited 

 from olefiant gas than from marsh-gas. 



The volumes of the two gases begin to increase rapidly at 

 once on sparking, and very soon double the volume of the 

 original is reached, so that the decomposition is no doubt 

 perfect. This result seems anomalous, when we call to mind 

 that acetylene is formed by the passage of the discharge 

 between electrodes of carbon in an atmosphere of hydrogen. 

 We are forced to the inevitable conclusion, which is rather 

 interesting, that acetylene is not formed when only one of the 

 electrodes is carbon, and that it is necessary that both the 

 electrodes be carbon in order that it be formed. 



Further, we must infer that it is very probable that acety- 

 lene is itself decomposed entirely when the two electrodes are 

 metals or when only one of them is carbon. 



The increment in volume when marsh-gas and olefiant gas 



