DEFINITE ELECTROLYTIC ACTION, WITH DIFFERENT SIZED ELECTRODES. 89 



smaller surface, and for a much shorter time than those at the plates ; hence less 

 solution and a greater collection. 



719. There was also another effect produced, especially by the use of large elec- 

 trodes, which was both a consequence and a proof of the solution of part of the gas 

 evolved there. The collected gaz, when examined, was found to contain small por- 

 tions of nitrogen. This I attribute to the presence of air dissolved in the acid used 

 for decomposition. It is a well-known fact, that when bubbles of a gas but slightly 

 soluble in water or solutions pass through them, the portion of this gas which is dis- 

 solved displaces a portion of that previously in union with the liquid : and so, in the 

 decompositions under consideration, as the oxygen dissolves, it displaces a part of the 

 air, or at least of the nitrogen, previously united to the acid ; and this proceeds most 

 extensively with large plates, because the gas evolved at them is in the most favour- 

 able condition for solution. 



720. With the intention of avoiding this solubility of the gases as much as possible, 

 I arranged the decomposing plates in a vertical position (707. 708.), that the bubbles 

 might quickly escape upwards, and that the downward currents in the fluid should 

 not meet ascending currents of gas. This precaution I found to assist greatly in pro- 

 ducing constant results, and especially in experiments to be hereafter referred to, in 

 which other liquids than dilute sulphuric acid, as for instance solution of potash, 

 were used. 



721. The irregularities in the indications of the measurer proposed, arising from 

 the solubility just referred to, are but small, and may be very nearly corrected by 

 comparing the results of two or three experiments. They may also be almost entirely 

 avoided by selecting that solution which is found to favour them in the least de- 

 gree (728.) ; and still further by collecting the hydrogen only, and using that as the 

 indicating gas ; for being much less soluble than oxygen, being evolved with twice the 

 rapidity and in larger bubbles (7170? it can be collected more perfectly and in greater 

 purity. 



722. From the foregoing and many other experiments, it results that variation in 

 the, size of the electrodes causes no variation in the chemical action of a given quantity 

 of electricity upon water. 



723. The next point in regard to which the principle of constant electro-chemical 

 action was tested, was variation of intensity. In the first place, the preceding expe- 

 riments were repeated, using batteries of an equal number of plates, strongly and 

 iveahly charged; but the results were alike. They were then repeated, using batteries 

 sonietimes containing forty, and at other times only five pairs of plates; but the results 

 were still the same. Variations therefore in the intensity, caused by difference in the 

 strength of charge, or in the number of alternations used, produced no difference as to 

 the equal action of large and small electrodes. 



724. Still these results did not prove that variation in the intensity of the current 

 was not accompanied by a corresponding variation in the electro-chemical effects, 



MDCCCXXXIV. N 



