M. Viard on the Electro-chemical Deportment of Oxygen. 251 



to that formed electro-chemically, that the oxide could intervene 

 by its reduction, which even then would be only partial. 



But, although denying this mode of action of the oxide, I am 

 prepared to admit a certain action. I am aware that, according 

 to the experiments of Davy, Becquerel and Marianini, the oxide 

 is negative with respect to the metal ; but I maintain still, that 

 the oxide acts only as a less oxidable body. A battery of copper 

 and oxide of copper, of zinc and oxide of zinc, is more or less 

 analogous to a battery of copper and platinum, of zinc and pla- 

 tinum, which we shall presently examine. 



With copper alone, free oxygen is essential to the current ; to 

 replace the metal by the oxide would be to accelerate the effect. 



With zinc and iron, in absence of free oxygen, a current would 

 be produced accompanied by a disengagement of hydrogen upon 

 the oxide without causing its decomposition. The presence of 

 free oxygen would determine a new kind of current, where the 

 affinity of free oxygen for hydrogen would join itself to that of 

 zinc for oxygen. 



When the water, instead of being pure, contains sulphate of 

 potash, sulphate of zinc, sulphuric acid, chlorides or hydrochloric 

 acid in solution, the actions are analogous. An observable cur- 

 rent corresponds to the formation of sulphate and oxide, or of 

 chloride and oxide upon the non-aerated plate ; and of potash, 

 soda, oxide of zinc, or water upon the aerated plate (fig. 5). 



At the same time, the aerated plate is the seat of superficial 

 currents of the same nature. 



All bodies thus formed have a tendency to react upon each 

 other ; nevertheless it is still possible to examine the formation, 

 as will be seen in another memoir. 



§ II. — On the influence exercised by oxygen in batteries composed 

 of two metals. 



In examining this subject, we shall first demonstrate, that in 

 a simple element the intensity of the current increases with the 

 quantity of oxygen dissolved. 



Experiments were made with aerated liquids, and with liquids 

 deprived of air by ebullition. The arrangement of the experi- 

 ments was the same as before, with the exception, that, instead 

 of bladders being attached to the tubes, the plates rested imme- 

 diately on the bottom of the vessels. One apparatus contained 

 boiled water, the other aerated water. 



Only a few of the series of results which were obtained will 

 be here cited ; they are those which correspond to marine salt. 



