Amalgamated Zinc in acidulated Water. 83 



while a strip of amalgamated zinc immersed in the same liquid 

 communicated with the other extremity : at the instant of com- 

 munication an energetic current was indicated, which how- 

 ever immediately diminished in intensity, and at the end of a 

 few minutes the needle returned to zero ; scarcely any gas was 

 evolved, and of the few bubbles which[appeared, as much could 

 be detected on the surface of the zinc as of the mercury. 



3. With the same arrangement I substituted for the mer- 

 cury a strip of platinum well amalgamated. In this case, as 

 before, after a few minutes the current became null, or so feeble 

 as to require a delicate instrument to indicate its existence; 

 and if, after the cessation of the current, the zinc was changed 

 for unamalgamated platinum, this latter evolved torrents of hy- 

 drogen, and the needle indicated a violent current in a con- 

 trary direction. 



4. With things arranged as in experiment 2. I employed 

 a solution of sulphate of copper as an electrolyte instead of 

 acidulated water : an energetic and constant current was pro- 

 duced, the mercury became amalgamated to saturation with 

 reduced copper, and the precipitation of copper upon this 

 amalgam continued as long as crystals of the sulphate were 

 added to the solution. 



By these experiments it appears that mercury, which in its 

 normal state is well known to be inefficient as the positive 

 metal of a voltaic combination, is in many cases equally in- 

 efficient as a negative metal, from its faculty of combining 

 with the cations of the electrolytes, which, rendering it equally 

 positive with the metal with which it is voltaically associated, 

 the opposed forces neutralise each other. But if, as in ex- 

 periment 4, the cation of the electrolyte is not of a highly 

 electro-positive character ; the zinc (or other associated metal) 

 retains its superior oxidability and the voltaic current is not 

 arrested. The application of these experiments to the phaeno- 

 mena presented by amalgamated zinc, is evident: all the hete- 

 rogeneous metals with which the zinc may be adulterated and 

 which form minute negative elements, being amalgamated, 

 become by polarization equally positive with the particles of 

 zinc, and consequently without the presence of another metal 

 to complete the circuit, all action is arrested, as in the case of 

 pure zinc. The fact of amalgamated zinc being positive with 

 respect to common zinc, of its precipitating copper from its 

 solutions, and other anomalies, are also explained by these 

 experiments. 



As, in a common voltaic combination of zinc and mercury 

 this effect is complicated by the variety of cations which are 

 transferred to the negative metal, for instance, hydrogen, zinc, 



G 2 



