44 M. Bequerel on the ElectrO'motivc Actions, fyc. [July, 



per with solution of sea salt ; the copper becomes negative, and 

 the solution positive. This result explains why a plate of cop- 

 per in contact with zinc or tin, as lately ascertained by Sir H. 

 Davy, is less acted on by the sea-water than when not in contact 

 with an electro-positive metal. It cannot be denied, that two 

 substances at the moment they combine are in different electri- 

 cal states, and that there is a certain relation between those 

 states and the chemical affinities. Now if we can modify those 

 electrical states, it is almost certain that we shall also modify 

 the play of affinities ; but we have seen that a plate of copper, 

 bv contact with a solution of sea-salt, becomes negative ; it 

 follows that if we touch the same metal with an electro-positive 

 metal, the copper will be placed between two bodies, each tend- 

 ing to impart the same kind of electricity, a condition which 

 we know will tend to annul the electro-motive action of the 

 copper on the solution of sea-salt. Thus, according to the 

 electro-chemical theory, circumstances are so arranged as to 

 weaken the chemical action of the solution of sea-salt on the 

 copper." 



The memoir concludes with pointing out a method by means 

 of electricity, of ascertaining the changes which some solutions 

 experience by contact with the air. 



Dissolve iron in nitric acid; filter the solution, and immerse 

 into it two laminae of platina, each communicating with one of 

 the extremities of the wire of the galvanometer ; leave one of the 

 wires in the solution, withdraw the other, and again immerse it ; 

 it will be positively electrified. 



The nitrates of copper and lead give similar results for a short 

 time ; nitrate of zinc produces no such effect. 



When the experiment is made in an atmosphere of hydrogen, 

 no electrical current is established, though all circumstances, 

 except the want of contact with the atmosphere, are precisely 

 similar in both experiments. 



" Hence the contact of atmospheric air is indispensable to 

 the production of the electrical current by the immersion of 

 platina laminae in several fresh-prepared nitrates ; but what is 

 the modification that is instantaneously effected in the liquid 

 adhering to the surface of the lamina withdrawn from the solu- 

 tion ? We can, to a certain extent, explain this : The solution of 

 a metal in nitric acid gives rise to several compounds : take iron, 

 for instance ; first deutoxide of azote is formed, and soon after 

 nitrous acid, a protonitrate and a deutonitrate ; by degrees the 

 deutoxide of azote passes to the state of nitrous acid, the proto- 

 nitrate to that of deutonitrate, and, after a certain time, only 

 deutonitrate remains in the liquid. According to this state- 

 ment, when we withdraw one of the platina laminae from the 

 solution, the liquid which adheres to it immediately, in conse- 

 quence of the thinness of the stratum, experiences changes from 



