ELECTROLYTIC INTENSITY REQUIRED FOR WATER, ETC. 453 



or lowered by the intervention of larger or smaller portions of bad conductors, 

 whether decomposable or not, before their relation can be minutely and fully un- 

 derstood. 



984. In the case of water, the experiments I have as yet made, appear to show, 

 that, when the electric current is reduced in intensity below the point required for 

 decomposition, then the degree of conduction is the same Avhether sulphuric acid, 

 or any other of the many bodies which can affect its transferring power as an elec- 

 trolyte, are present or not. Or, in other words, that the necessary electrolytic in- 

 tensity for water is the same whether it be pure, or rendered a better conductor by 

 the addition of these substances ; and that for currents of less intensity than this, the 

 water, whether pure or acidulated, has equal conducting power. An apparatus, 

 fig. 12, was arranged with dilute sulphuric acid in the vessel A, and pure distilled wa- 

 ter in the vessel B. By the decomposition at e, it appeared as if water was a better 

 conductor than dilute sulphuric acid for a current of such low intensity as to cause 

 no decomposition. I am inclined, however, to attribute this apparent superiority of 

 water to variations in that peculiar condition of the platina electrodes which is re- 

 ferred to further on in this Series (1040.), and which is assumed, as far as I can 

 judge, to a greater degree in dilute sulphuric acid than in pure water. The power, 

 therefore, of acids, alkalies, salts, and other bodies in solution, to increase conduct- 

 ing power, appears to hold good only in those cases where the electrolyte subject to 

 the current suffers decomposition, and loses all influence when the current trans- 

 mitted has too low an intensity to effect chemical change. It is probable that the or- 

 dinary conducting power of an electrolyte in the solid state (419.) is the same as that 

 which it possesses in the fluid state for currents under the due electrolytic intensity. 



985. Currents of electricity, produced by less than eight or ten series of voltaic 

 elements, can be reduced to that intensity at which water can conduct them without 

 suffering decomposition, by causing them to pass through three or four vessels in 

 which water shall be successively interposed between platina surfaces. The prin- 

 ciples of interference upon which this effect depends, will be described hereafter 

 (1009. 1018.), but the effect may be useful in obtaining currents of standard inten- 

 sity, and is probably applicable to batteries of any number of pairs of plates. 



986. As there appears every reason to expect that all electrolytes will be found 

 subject to the law which requires an electric current of a certain intensity for their 

 decomposition, but that they will differ from each other in the degree of intensity 

 required, it will be desirable hereafter to arrange them in a table, in the order of 

 their electrolytic intensities. Investigations on this point must, however, be very 

 much extended, and include many more bodies than have been here mentioned 

 before such a table can be constructed. It will be especially needful in such experi- 

 ments, to describe the nature of the electrodes used, or, if possible, to select such as, 

 like platina or plumbago in certain cases, shall have no power of assisting the sepa- 

 ration of the ions to be evolved (913.). 



MDCCCXXXIV. 3 N 



