of Aqueous and Alco/tolic Solutions. 2i7 



towards the positive side reacted with the hydrogen of the 

 water in B, it is plain that the hydracid so formed should 

 have been immediately decomposed again, and the chlorine 

 or iodine should have speedily appeared at the pole in a se- 

 parate form, and that before acid appeared ; whereas in the 

 case of muriatic acid, the chlorine did not appear till consi- 

 derably after acid had passed into B, and much later than 

 iodine appeared in the case of hydriodic acid, although the 

 constituents of the latter are less decidedly opposed to one an- 

 other in electric nature than those of muriatic acid, and there- 

 fore ought reasonably to be of more difficult voltaic decom- 

 position. The quantity of chlorine or iodine which appears is 

 not in proportion to the absolute quantity of acid which passes 

 over, but to the facility with which that acid is reduced. The 

 fair and natural interpi-etation of the whole phsenomena, is 

 evidently afforded on the view of a secondary action on the 

 hydracid. 



The experiment with hydriodic acid was varied by connect- 

 ing two tubes, B and C, fig. 2, each filled with distilled water, 

 with the tube A, containing the hydriodic solution, the power 

 being seventy pairs of four-inch plates. Slight effervescence 

 ensued at both poles, but during forty minutes' action no dis- 

 coloration appeared in either tube. Soon after a brown tint 

 appeared in C, with acid reaction at the positive pole. In 

 ten minutes more the battery was reversed, when iodine 

 without any gas instantly appeared in A. All these appear- 

 ances are quite in conformity with the above views. 



In regard to metallic oxides it is not easy to obtain such 

 direct experimental evidence, because the metals of such as 

 are soluble in water react on the solvent; but we may take 

 the decomposition of metallic oxides as contained in solu- 

 ble salts, during which the metal frequently appears at the 

 negative pole, as illustrating the action on solutions of such 

 oxides as are dissolved by pure water. It is now pretty ge- 

 nerally admitted, that when metal appears in solutions of 

 metallic salts at the negative pole, it is due to the reducing 

 action of nascent hydrogen ; and this opinion I have verified 

 directly by finding, that when solutions of sulphate of copper, 

 or muriate of zinc or nitrate of silver, were made positive by 

 fifty pairs of two-inch plates, and connected by asbestus with 

 distilled water which was made negative, neither metal nor 

 oxide was carried towards the negative pole during half an 

 hour's action ; whilst on reversal of the battery, the non-nega- 

 tive foil in a quarter of an hour was found to be more or less 

 covered with reduced metal. Thus tlie circumstance that 

 in the one position nascent hydrogen was produced in the 



