366 Intelligence and Miscellaneous Articles. 



in ordinary circumstances is set up between mercury and sulphuric 

 acid. 



M. Lippmann found this value equal to about 0-9 volt ; I myself 

 have found it to be 0-86 volt. This difference is due to difference 

 of concentration of the sulphuric acid ; that which M. Lippmann 

 used was about -i-, while that which I used was about -^. 



The difference of potential between mercury and sulphuric acid 

 is thus really 0-86 to 0-9 volt, according to the concentration of 

 the acid ; if then Dr. Moser found a different value of 0-4 volt, it 

 is a decisive proof that Dr. Moser's electrodes do not furnish the 

 true potential of the electrolytes. — Comptes Rendus, February 25, 

 1889. 



ON ELECTROLYSIS. BY MM. VIOLLE AND CHASSAGNY. 



The decomposition of water by means of a powerful current is 

 accompanied by luminous and calorific phenomena, which were 

 noticed more than forty years ago by MM. Fizeau and Foucault*, 

 and since then investigated by a large number of physicists. The 

 use of a Gramme machine which ca*i furnish 40 amperes with an 

 electromotive force of 110 volts has^enabled us readily to obtain 

 these phenomena, to observe them in well-defined conditions, and 

 to call attention to some new facts. 



In water containing -jiy sulphuric acid (with a smaller proportion 

 the phenomena are less w^ll marked) a platinum wire 4;5 millim. 

 in diameter was immersed. The negative electrode was a platinum 

 wire 1*6 millim. in diameter, which was very slowly immersed in 

 the cold liquid. 



If the difference of potential at the binding-screws of the volta- 

 meter is above 32 volts, a luminous sheath is observed about the 

 negative wire, which stands out from the liquid, and in which the 

 disengagement of hydrogen alone takes place. It offers a powerful 

 resistance to the passage of the current, which slowly diminishes 

 as the sheath extends, on penetrating the liquid with the wire, and 

 which suddenly falls the moment the sheath disappears to give 

 place to the ordinary disengagement by bubbles. The following 

 table indicates the maximum length I which the sheath can attain 

 for a given electromotive force E in a cold liquid ; I is the indica- 

 tion of a Deprez-Carpentier's ammeter in the circuit. 



* Annales de Chiwie, 3rd series, vol. xi. p. 383 (1844). 



