On the Movements of Liquid Metals in the Voltaic Circuit. 159 



Numerous interesting phenomena of motion and of colour, especially 

 with solutions of salts of the earth-metals and with metallic iodides, 

 were observed during the examination. 



36. On examining these numerous results we find : — 1st. That all 

 alkalies and some alkaline salts produce a positive flow only. 2nd. 

 That some alkaline and many neutral salts produce both positive and 

 negative flows. 3rd. That some neutral and many acid salts, 

 and nearly all acids, both organic and inorganic, produce a negative 

 flow only. The stronger influence of acids, compared to that of 

 alkalies (14, Note) in the production of these movements, is pro- 

 bably the reason why various salts of alkaline reaction give a negative 

 as well as a positive flow, ancfc why many neutral salts containing a 

 strong acid (chlorides, for example) give a negative flow only. No 

 substance of alkaline reaction has been observed to give a negative 

 flow only, nor any strongly acid substance to give only a positive 

 flow. An alkaline or electro-positive substance as the electrolyte, 

 produces therefore by the 3rd method a positive flow, and an acid 

 or electro-negative substance produces a negative flow. Numerous 

 analogies may be detected in the behaviour of similar salts on ex- 

 amining the Table. 



37. The movements obtained by the 3rd method appear to be 

 results of a similar mutual attraction of the mercury and the ele- 

 ments of the liquid to those obtained by methods I and 2. The 

 mercury moves towards the cathode in acids because its positive end 

 has acquired, by the aid of the electric current, a stronger affinity for 

 the negative element of the liquid than its negative end has for the 

 positive element, and moves towards the anode in alkalies because 

 its negative end has acquired a stronger attraction for the positive 



