432 DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. 



bodies were now decomposed which resisted any current tending to be formed by the 

 dilute sulphuric acid. For instance, muriatic acid could not be decomposed by a 

 single pair of plates when immersed in dilute sulphuric acid ; nor did making the 

 sulphuric acid strong, nor enlarging the size of the zinc and platina plates immersed 

 in it, increase the power ; but if to a weak sulphuric acid a very little nitric acid was 

 added, then the electricity evolved had power to decompose the muriatic acid, 

 evolving chlorine at the anode and hydrogen at the cathode, even when mere wires of 

 metals were used. This mode of increasing the intensity of the electric current, as it 

 excludes the effect dependent upon many pairs of plates, or even the effect of making 

 any one acid stronger or weaker, is at once referable to the condition and force of 

 the chemical affinities which are brought into action, and may, both in principle and 

 practice, be considered as perfectly distinct from any other mode. 



909. The direct reference which is thus experimentally made in the simple voltaic 

 circle of the intensity of the electric current to the intensity of the chemical action 

 going on at the place where the existence and direction of the current is determined, 

 leads to the conclusion that by using selected bodies, as fused chlorides, salts, solu- 

 tions of acids, &c., which may act upon the metals employed with different degrees of 

 chemical force ; and using also metals in association with platina, or with each other, 

 which shall differ in the degree of chemical action exerted between them and the ex- 

 citing fluid or electrolyte, we should be able to obtain a series of comparatively con- 

 stant effects due to electric currents of different intensities, which would serve to 

 assist in the construction of a scale so as to supply the means of determining relative 

 degrees of intensity accurately in future researches. 



910. I have already expressed the view which I take of the decomposition in the 

 experimental place, as being the direct consequence of the superior exertion at some 

 other spot of the same kind of power as that to be overcome, and therefore as the 

 result of an antagonism of forces of the same nature (891. 904.). Those at the place 

 of decomposition have a reaction upon, and a power over, the exerting or determining 

 set proportionate to what is needful to overcome their own power ; and hence a cu- 

 rious result of resistance offered by decompositions to the original determining force, 

 and consequently to the current. This is well shown in the cases where such bodies 

 as chloride of lead, iodide of lead, and water would not decompose with the current 

 produced by a single pair of zinc and platina plates in sulphuric acid (903.), although 

 they would with a current of higher intensity produced by stronger chemical powers. 

 In such cases no sensible portion of the current passes (967.) ; the action is stopped : 

 and I am now of opinion that in the case of the law of conduction which I described 

 in the Fourth Series of these Researches (413.), the bodies which are electrolytes in the 

 fluid state cease to be such in the solid form, because the attractions of the particles 

 by which they are retained in combination and in their relative position, are then too 

 powerful for the electric current. The particles retain their places ; and as decompo- 



