44 Dr. Faraday's Experimental Researches in Electricity, 



ed, the transmission of the electricity is prevented also ; and 

 although a battery of many plates may be used, yet if it be of 

 that perfect kind which allows of no extraneous or indirect ac- 

 tion (1000.), the whole of the affinities concerned in the acti- 

 vity of that battery are at the same time also suspended and 

 counteracted. 



911. But referring to the resistance of each single case of 

 decomposition, it would appear that as these differ in force 

 according to the affinities by which the elements in the sub- 

 stance tend to retain their places, they also would supply cases 

 constituting a series of degrees by which to measure the initial 

 intensities of simple voltaic or other currents of electricity, 

 and which, combined with the scale of intensities determined 

 by different degrees of actirig force (909.), would probably 

 include a sufficient set of differences to meet almost every im- 

 portant case where a reference to intensity would be required. 



912. According to the experiments I have already had oc- 

 casion to make, 1 find that the following bodies are electroly- 

 tic in the order in which I have placed them, those which are 

 first being decomposed by the current of lowest intensity. 

 These currents were always from a single pair of plates, and 

 may be considered as elementary voltaic forces. 



Iodide of potassium (solution). 



Chloride of silver (fused). 



Prolochloride of tin (fused). 



Chloride of lead (fused). 



Iodide of lead (fused). 



Muriatic acid (solution). 



Water, acidulated with sulphuric acid. 



913. It is essential that in all endeavours to obtain the re- 

 lative electrolytic intensity necessary for the decomposition of 

 different bodies, attention should be paid to the nature of the 

 electrodes, and [to that of] the other bodies present which may 

 favour secondary actions (986.). If in electro-decomposition 

 one of the elements separated has an affinity for the electrode, 

 or for bodies present in the surrounding fluid, then the affinity 

 resisting decomposition is in part balanced by such power, and 

 the true place of the electrolyte in a table of the above kind is 

 not obtained : thus, chlorine combines with a positive platina 

 electrode freely, but iodine scarcely at all, and therefore I be- 

 lieve it is that the chloride stands first in the preceding table. 

 Again, if in the decomposition of water not merely sulphuric 

 but also a little nitric acid be present, then the water is more 

 freely decomposed, for the hydrogen at the cathode is not ulti- 

 mately expelled, but finds oxygen in the nitric acid, with 

 which it can combine to produce a secondary result ; the af- 

 finities opposing decomposition are in this way diminished. 



