98 DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. 



commonly received by all. The change of my own opinion requires that I should 

 correct what I have already said of the decomposition of sulphuric acid in a former 

 series of these Researches (552.) ; I do not now think that the appearance of the sul- 

 phur at the negative electrode is an immediate consequence of electrolytic action. 



758. Muriatic acid. — A strong solution gave hydrogen at the negative electrode, 

 and chlorine only at the positive electrode ; of the latter, a part acted on the platina 

 and a part was dissolved. A minute bubble of gas remained ; it was not oxygen, but 

 probably air previously held in solution. 



759. It was an important matter to determine whether the chlorine was a primary 

 result, or only a secondary product, due to the action of the oxygen evolved from 

 water at the anode upon the muriatic acid ; i. e. whether the muriatic acid was elec- 

 trolyzable, and if so, whether the decomposition was definite. 



760. The muriatic acid was gradually diluted. One part with six of water gave 

 only chlorine at the anode. One part with eight of water gave only chlorine ; with 

 nine of water, a little oxygen appeared with the chlorine : but the occurrence or non- 

 occurrence of oxygen at these strengths depended, in part, on the strength of the 

 voltaic battery used. With fifteen parts of water, a little oxygen, with much chlo- 

 rine, was evolved at the anode. As the solution was now becoming a bad conductor 

 of electricity, sulphuric acid was added to it : this caused more ready decomposition, 

 but did not sensibly alter the proportion of chlorine and oxygen. 



761. The muriatic acid was now diluted with 100 times its volume of dilute sul- 

 phuric acid. It still gave a large proportion of chlorine at the anode, mingled with 

 oxygen ; and the result was the same, whether a voltaic battery of 40 pairs of plates 

 or one containing only 5 pairs were used. With acid of this strength, the oxygen 

 evolved at the anode was to the hydrogen at the cathode, in volume, as 17 is to 64 ; 

 and therefore the chlorine would have been 30 volumes, had it not been dissolved by 

 the fluid. 



762. Next, with respect to the quantity of elements evolved. On using the volta- 

 electrometer, it was found that, whether the strongest or the weakest muriatic acid 

 were used, whether chlorine alone or chlorine mingled with oxygen appeared at the 

 anode, still the hydrogen evolved at the cathode was a constant quantity, i. e. exactly 

 the same as the hydrogen which the same quantity of electricity could evolve from 

 water. 



763. This constancy does not decide whether the muriatic acid is electrolyzed or 

 not, although it proves that if so, it must be in definite proportions to the quantity of 

 electricity used. Other considerations may, however, be allowed to decide the point. 

 The analogy between chlorine and oxygen, in their relations to hydrogen, is so stiong, 

 as to lead almost to the certainty, that, when combined with that element, they would 

 perform similar parts in the process of electro-decomposition. They both unite with it 

 in single proportional or equivalent quantities ; and, the number of proportionals 

 appearing to have an intimate and important relation to the decomposability of a 



