Definite Electrolytic Action, with different-shed Electrodes. 175 



73*25 volumes ; whilst the sum of the oxygen and hydrogen 

 in two separate tubes amounted to 73*65 volumes. In an- 

 other experiment the volumes were 55*3, 55*3, and 54'4-. 



716. But it was observed in these experiments, that in 

 single-plate tubes (707.) more hydrogen was evolved at the 

 negative electrode than was proportionate to the oxygen at 

 the positive electrode; and generally, also, more than was 

 proportionate to the oxygen and hydrogen in a double-plate 

 tube. Upon more minutely examining these effects, I was 

 led to refer them, and also the differences between wires and 

 plates (714-.), to the solubility of the gases evolved, especially 

 at the positive electrode. 



717. When the positive and negative electrodes are equal 

 in surface, the bubbles which rise from them in dilute sul- 

 phuric acid are always different in character. Those from 

 the positive plate are exceedingly small, and separate instantly 

 from every part of the surface of the metal, in consequence 

 of its perfect cleanliness (633.) ; whilst in the liquid they give 

 it a hazy appearance, from their number and minuteness ; are 

 easily carried down by currents ; and therefore not only pre- 

 sent far greater surface of contact with the liquid than larger 

 bubbles would do, but are retained a much longer time in 

 mixture with it. But the bubbles at the negative surface, 

 though they constitute twice the volume of the gas at the po- 

 sitive electrode, are nevertheless very inferior in number. 

 They do not rise so universally from every part of the sur- 

 face, but seem to be evolved at different points ; and though 

 so much larger, they appear to cling to the metal, separating 

 with difficulty from it, and when separated, instantly rising to 

 the top of the liquid. If, therefore, oxygen and hydrogen 

 had equal solubility in, or powers of combining with, water 

 under similar circumstances, still under the present conditions 

 the oxygen would be far the most liable to solution ; but when 

 to these is added its well-known power of forming a com- 

 pound with water, it is no longer surprising that such a com- 

 pound should be produced in small quantities at the positive 

 electrode; and indeed the bleaching power which some philo- 

 sophers have observed in a solution at this electrode, when 

 chlorine and similar bodies have been carefully excluded, is 

 probably due to the formation there, in this manner, of oxy- 

 water. 



718. That more gas was collected from the wires than from 

 the plates, I attribute to the circumstance, that as equal quan- 

 tities were evolved in equal times, the bubbles at the wires 

 having been more rapidly produced, in relation to any part of 

 the surface, must have been much larger ; have been there- 



