Phenomena of the Capillary Electroscope. 



91 



wires excited by a mixture of 1 volume of sulphuric acid and 19 of 

 water. I ascertained by experiment that the former current had the 

 greatest electromotive force. 



1 oz. of water and 40 grs. of potassic cyanide, and a current from 

 copper and platinum wires in the solution of cyanide (60 grs. per oz.) 

 above mentioned. With a short length of mercury in a horizontal 

 tube less coarse than the last, the mercury moved in each direction 

 opposite to the current a distance of about 13 millims. 



Also by employing a platinum electrode without any mercury upon 

 it, below the vertical capillary, all the movements occurred as usual. 

 These latter experiments prove that the lower electrode need not be 

 composed of a fluid metal, and therefore that I might have omitted to 

 make the previous one respecting the influence of relative dimensions 

 of the two mercurial electrodes. 



3. Influence of Molecular Structure, Cohesion, Liquidity, Viscosity, and 

 Pressure upon the Movements. 



That the molecular structures of the mercury and solution affect 

 the phenomena is quite certain, because we know that the physical 

 properties in general of substances depend essentially upon their 

 internal architecture ; the intimate structure of bodies, however, is so 

 inscrutable, that investigation has not yet disclosed it clearly to us. 

 As a solid metal in place of the mercury will not admit of either of 

 the movements, the molecular motion in each liquid is a relative one ; 

 the motion of the one liquid depends upon the liquid state of the 

 other. The movement is also dependent upon the kind of molecular 

 structure of the solution : 1st, because it varies in direction with a 

 variation in the kind of solution : and 2nd, because it varies also with 

 a variation of strength of the solution ; and in each case without any 

 evidence of chemical or electro-chemical action. 



Cohesion of the mercury influences the movements, and tends to 

 cause that substance to move more readily from a narrower to a wider 

 part of the tube than in the reverse direction. 



As the liquid state of the lower electrode was not a necessary con- 

 dition of the motions, the movement of one electrode is not at all 

 dependent upon a similar movement of the other. A single liquid 

 electrode is sufficient to exhibit all the phenomona. Fused salts 

 might probably be used with success, instead of aqueous solutions. 

 (See " Movements of Liquid Metals and Electrolytes in the Voltaic 

 Circuit," " Proc. Roy. Soc," vol. 10, par. 10.) 



The movement was constantly found to diminish as the viscosity of 

 the solution was increased beyond a certain point, by addition of 

 saline or other solid or viscous substance. Pressure probably has but 

 little influence, because liquids are so slightly compressible. 



