Primary and Secondary Results of Electrolytic Action. 255 



decomposition, as pure water; but when sulphate of ammonia 

 is dissolved in it, the whole becomes a conductor; nitrogen 

 almost and occasionally quite pure is evolved at the anode, and 

 hydrogen at the cathode; the ratio of the volume of the former 

 to that of the latter varying, but being as 1 to about 3 or 4. 

 This result would seem at first to imply that the electric cur- 

 rent had decomposed ammonia, and that the nitrogen had 

 been determined towards the positive electrode. But when 

 the electricity used was measured out by the volta-electrome- 

 ter (707. 736.), it was found that the hydrogen obtained was 

 exactly in the proportion which would have been supplied by 

 decomposed water, whilst the nitrogen had no certain or con- 

 stant relation whatever. When, upon multiplying experiments, 

 it was found that, by using a stronger or weaker solution, or 

 a more or less powerful battery, the gas evolved at the anode 

 was a mixture of oxygen and nitrogen, varying both in pro- 

 portion and absolute quantity, whilst the hydrogen at the 

 cathode remained constant, no doubt could be entertained that 

 the nitrogen at the anode was a secondary result, depending 

 upon the chemical action of the nascent oxygen, determined 

 to that surface by the electric current, upon the ammonia in 

 solution. It was the water, therefore, which was electrolyzed, 

 not the ammonia. Further, the experiment gives no real in- 

 dication of the tendency of the element nitrogen to either one 

 electrode or the other; nor do I know of any experiment with 

 nitric acid, or other compounds of nitrogen, which shows the 

 tendency of this element, under the influence of the electric 

 current, to pass in either direction along its course. 



749. As another illustration of secondary results, the effects 

 on a solution of acetate of potassa may be quoted. When a 

 very strong solution was used, more gas was evolved at the 

 anode than at the cathode, in the proportion of 4 to 3 nearly : 

 that from the anode was a mixture of carbonic oxide and car- 

 bonic acid ; that from the cathode pure hydrogen. When a 

 much weaker solution was used, less gas was evolved at the 

 anode than at the cathode; and it now contained carburetted hy- 

 drogen, as well as carbonic oxide and carbonic acid. This 

 result of carburetted hydrogen at the positive electrode has a 

 very anomalous appearance, if considered as an immediate 

 consequence of the decomposing power of the current. It, 

 however, as well as the carbonic oxide and acid, is only a se- 

 condary result ; for it is the water alone which suffers electro- 

 decomposition, and it is the oxygen eliminated at the anode 

 which, reacting on the acetic acid, in the midst of which it is 

 evolved, produces those substances that finally appear there. 

 This is fully proved by experiments with the volta-electrome- 



