88 DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. 



715. Experiments of a similar kind were made with the single-plate, straight 

 tubes {707.), and also with the curved tubes (708.), with similar consequences; and 

 when these, with the former tubes, were arranged together in various ways, the re- 

 sult, as to the equality of action of large and small metallic surfaces when delivering 

 and receiving the same current of electricity, was constantly the same. As an illus- 

 tration, the following numbers are given. An instrnment with two wires evolved 

 74'3 volumes of mixed gases ; another with plates 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. 



7 16. But it was observed in these experiments, that in single-plate tubes (707.) 

 more hydrogen was evolved at the negative electrode than was propoitionate 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 elec- 

 trode. 



717- When the positive and negative electrodes are equal in surface, the bubbles 

 which rise from them in dilute sulphuric 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 present 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 positive electrode, are nevertheless very 

 inferior in number. They do not rise so universally from every part of the surface, 

 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 solu- 

 bility 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 compound with water, it is no 

 longer surprising that such a compound should be produced in small quantities at 

 the positive electrode ; and indeed the bleaching power which some philosophers 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. 



7 18. That more gas was collected from the wires than from the plates, I attribute 

 to the circumstance, that as equal quantities 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 therefore in contact with the fluid by a much 



