260 Dr. Faraday's Experimental Researches in Electricity, 



water is electro- chemically decomposed, giving origin to the 

 oxygen, which appears mingled with the chlorine at the anode. 

 The oxygen may be viewed as a secondary result ; but I in- 

 cline to believe that it is not so: for, if it were, it might be 

 expected in largest proportion from the stronger acid, whereas 

 the reverse is the fact. This consideration, with others, also 

 leads me to conclude that muriatic acid is more easily decom- 

 posed by the electric current than water; since, even when 

 diluted with eight or nine times its quantity of the latter fluid, 

 it alone gives way, the water remaining unaffected. 



766. Chlorides, — On using solutions of chlorides in water, 

 — for instance, the chlorides of sodium or calcium, — there 

 was evolution of chlorine only at the positive electrode, and 

 of hydrogen, with the oxide of the base, as soda or lime, at 

 the negative electrode. The process of decomposition may 

 be viewed as proceeding in two or three ways, all terminating 

 in the same results. Perhaps the simplest is to consider the 

 chloride as the substance electrolyzed, its chlorine being deter- 

 mined to and evolved at the anode, and its metal passing to 

 the cathode, where, finding no more chlorine, it acts upon the 

 water, producing hydrogen and an oxide as secondary results. 

 As the discussion would detain me from more important mat- 

 ter, and is not of immediate consequence, I shall defer it for 

 the present. It is, however, of great consequence to state, that, 

 on using the volta-electrometer, the hydrogen in both cases 

 was definite ; and if the results do not prove the definite de- 

 composition of chlorides, (which shall be proved elsewhere, — 

 789. 794*. 814,) they are not in the slightest degree opposed 

 to such a conclusion, and do support the general law, 



767. Hydriodic Acid,— A solution of hydriodic acid was 

 affected exactly in the same manner as muriatic acid. When 

 strong, hydrogen was evolved at the negative electrode, in 

 definite proportion to the quantity of electricity which had 

 passed, i. e, in the same proportion as was evolved by the 

 same current from water; and iodine without any ox}'gen was 

 evolved at the positive electrode. But when diluted, small 

 quantities of oxygen appeared with the iodine at the anode, 

 the proportion of hydrogen at the cathode remaining undis- 

 turbed. 



768. I believe the decomposition of the hydriodic acid in 

 this case to be direct, for the reasons already given respecting 

 muriatic acid (763. 764?.). 



769. Iodides, — A solution of iodide of potassium being sub- 

 jected to the voltaic current, iodine appeared at the positive 

 electrode (without any oxygen), and hydrogen with free alkali 

 at the negative electrode. The same observations as to the 



