PRIMARY AND SECONDARY RESULTS OF ELECTROLYZATIOX. 99 



body (697.)j those in muriatic acid, as well as in water, are the most favourable, or those, 

 perhaps even necessary, to decomposition. Inother binary compounds of chlorine also, 

 where nothing equivocal depending on the simultaneous presence of it and oxygen is in- 

 volved, the chlorine is directly eliminated at the anode by the electric current. Such 

 is the case with the chloride of lead (395.), which may be justly compared with prot- 

 oxide of lead (402.), and stands in the same relation to it as muriatic acid to water. 

 The chlorides of potassium, sodium, barium, &c., are in the same relation to the prot- 

 oxides of the same metals, and present the same results under the influence of the 

 electric current (402.). 



764. From all the experiments, combined with these considerations, I conclude that 

 muriatic acid is decomposed by the direct influence of the electric current, and that 

 the quantities evolved are, and therefore the chemical action is, definite for a definite 

 quantity of electricity. For though I have not collected and measured the chlorine, in 

 its separate state, at the anode, there can exist no doubt as to its being proportional 

 to the hydrogen at the cathode ; and the results are therefore sufficient to establish the 

 general law of constant electro-chemical action in the case of muriatic acid. 



765. In the dilute acid (761.)? I conclude that a part of the water is electro-chemi- 

 cally decomposed, giving origin to the oxygen, which appears mingled with the chlo- 

 rine at the anode. The oxygen may be viewed as a secondary result ; but I incline 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 decomposed 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 chlo- 

 rides of sodium or calcium, — there was evolution of chlorine only at the positive elec- 

 trode, 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 determined 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 re- 

 sults. As the discussion would detain me from more important matter, and is not of 

 immediate consequence, I shall defer it for the present. It is, however, of great con- 

 sequence to state, that, on using the volta-electrometer, the hydrogen in both cases 

 was definite ; and if the results do not prove the definite decomposition 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 aflfected exactly in tjie same 

 manner as muriatic acid. When strong, hydrogen was evolved at the negative elec- 

 trode, in definite proportion to the quantity of electricity which had passed, i. e. in 



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