of Electrical and Chemical Changes. 97 



been tarnished by the action of nitric acid, is negative to po- 

 lished silver in diluted acid; and gold and platinum, that have 

 been acted on by aqua regia, are negative in that acid to the 

 clean metals. 



The intimate connexion displayed in all these cases be- 

 tween the chemical and electrical phaenomena, becomes still 

 more remarkable when the nature of the changes taking place 

 in circles of this kind is considered. 



Oxvo-en, which may be considered as negative with respect 

 to alfthe metals, and sulphur, which is negative wiih respect 

 to the oxidable metals, by their combinations with metals re- 

 spectively positive to them, produce compounds negative with 

 regard to those metals. And in the chemical changes, the 

 results are such as must uhimately restore the equilibrium, 

 hydrogen or sulphuretted hydrogen passing to the negative 

 side, and oxygen to the positive side ; so that the oxides are 

 revived; and not only is the equilibrium restored, but the 

 poles sometimes changed. Thus tin that has tarnished in 

 acid, remains for some time negative in solution of alkali, but 

 gradually as the oxide upon it is revived by the hydrogen de- 

 termined to this surface, it loses its negative power ; and the 

 other surface, now tarnished by the action of the alkali, gains 

 this power, whilst the opposite surface becomes positive. 



V. Of electrical combivalions, consisting of two imperfect, and, 

 one -perfect conductor; or ivoofuids and a metal, or charcoal. 

 To understand clearly the nature of the action in this kind 

 of electrical combination, it is necessary to consider the na- 

 ture of imperfect conducting bodies, water, or saline solutions. 

 These bodies may be regarded as having the same relations 

 to electricities of very low intensity, that elastic fluids have to 

 the electricities of glass, sealing-wax, or the common machine. 

 They communicate the electrical polarities of the metals, 

 but do not appear capable of receiving such polarities, or at 

 least of retaining them; and the electrical equilibrium, when 

 broken in them, seems to be rapidly restored by a new ar- 

 rangement or attraction of certain of their elements. For in- 

 stance, if we introduce the positive and negative poles from 

 a very powerful voltaic battery into the extremities of a basin 

 filled with solution of muriate of lime, and place in the circuit 

 different wires of platinum, every wire will possess a positive 

 and negative pole, and there will be no division of the fluid 

 into two parts, one positive, the other negative ; and when the 

 two wires are withdrawn, they alone having been used, the 

 electrical appearances immediately cease ; and metallic wires 

 unconnected with the battery made to occupy their places, ex- 

 hibit no electrical phaenomena : and in all experiments ot this 

 New Series. Vol. 1. No. 2. FeO. 1827. O kind, 



