54 



Action of Metals in Electrolytes. 



[Nov. 22 r 



corrosion of the negative to that of the positive one was increased 

 from 3 11 to 6-32. 



The theory most consistent with all the various results and conclu- 

 sions is a kinetic one. That metals and electrolytes are throughout 

 their mass in a state of molecular vibration. That the molecules of 

 these substances being frictionless bodies irt a frictionless medium, and 

 their motion not being dissipated by conduction or radiation, they 

 continue incessantly in motion until some cause arises to prevent 

 them. That each metal (or electrolyte) when unequally heated has,, 

 to a certain extent, an unlike class of motions in its differently heated 

 parts, and behaves in those parts somewhat like two metals (or elec- 

 trolytes), and those unlike motions are enabled through the inter- 

 mediate conducting portion of the substance to render these parts 

 electro-polar. That every different metal and electrolyte has a different 

 class of motions, and in consequence of this they also by contact 

 alone with each other at the same temperature become electro-polar. 

 The molecular motion of each different substance also increases at 

 a different rate by rise of temperature. 



This theory is equally in agreement with the chemico-electric 

 results. In accordance with it, when in the case of a metal and an 

 electrolyte the two classes of motions are sufficiently unlike, chemical- 

 corrosion of the metal by the liquid takes place, and the voltaic 

 current originated by inherent molecular motion under the condition 

 of contact, is maintained by the portion of motion lost by the metal 

 and liquid during the act of uniting together. Corrosion, therefore,, 

 is an effect of molecular motion, and is one of the modes by which 

 that motion is converted into electric current. 



In accordance with this theory, if we take a thermo-electric pair 

 consisting of a non-corrodible metal and an electrolyte (the two 

 being already electro-polar by mutual contact), and heat one of their 

 points of contact, the molecular motion of the heated end of each 

 substance at the junction is altered ; and as thermo-electric energy in 

 such combinations usually increases by rise of temperature, the metal 

 and liquid, each singly, usually becomes more electro-polar. In such 

 a case the unequally heated metal behaves to some extent like two 

 metals, and the unequally heated liquid like two liquids, and so the 

 thermo-electric pair is like a feeble chemico-electric one of two metals 

 in two liquids, but without corrosion of either metal. If the metal 

 and liquid are each when alone thermo-electro-positive, and if when in 

 contact the metal increases in positive condition faster than the 

 liquid by being heated, the latter appears thermo-electro-negative, 

 but if less rapidly than the liquid, the metal appears thermo-electro- 

 negative. 



As also the proportion of instances is small in which metals that 

 are positive in the ordinary thermo-electric series of metals only,. 



