M. BECaUEREL ON CHEMICAL EFFECTS OF ELECTRICAL ACTION. 4-15 



it is obvious that metals can form, with theii- own solutions and pure 

 or acidulated water, currents whose electrical action precipitates the 

 metal. In this case there are two electrical effects : the one caused by 

 the re-action of the two liquids one on the other ; the second by the 

 action of the acidulated water on the metallic plate ; it is therefore a 

 compound phsenomenon, for the actions are added or subtracted ac- 

 cording as they have the same or contrary directions. In the case under 

 consideration the two actions are coml^ined. Certain thermo-electrical 

 phaenomena and simple chemical actions ordinarily disengage electricity 

 enough to produce decompositions resembling those just mentioned. 



Let us first direct our attention to the decompositions produced by 

 thermo-electi'ical currents. 



2. Several experimentalists have tried to decompose water with thermo- 

 electrical currents, but in vain; for in order to succeed, they should have 

 experimented with salts decomposable by a weak current, such as ni- 

 trate of silver and iodide of potassium, and disposed the apparatus so 

 as to be able to determine the production of a new compound. 



Let us take two wires, the one of platina tiie other of copper, of a 

 certain length and about ^ of a millimetre* in diameter ; forming at 

 one end of each wire a ring, and hook one ring on the other ; the ring 

 of the jilatina wire being very small, and that of the copper wire about 

 three millimetres in diameter. If we solder the two rings, the cur- 

 rent goes always in the same direction, from the platina to the copper, 

 whether we heat the wire to the right or to the left of the points of junc- 

 tion. Let us now solder a copper wire to the free end of the platina 

 wire, after which burn a small quantity of sulphur upon the copper ring, 

 and then place under the platina ring an alcohol lamp, so as to raise its 

 temperature to red heat, keeping the copper ring as cool as possible, 

 which may be done by placing the platina wire at the extremity of the 

 white flame, so that this may be at very little distance from the copper 

 ring. Now if we communicate the free ends of the copper wires with the 

 ends of the wire which forms the circuit of a galvanometer, ^^ e obtain a 

 current of electricity of considerable energy passing from the platina to 

 the copper. 



The copper ring is made larger than the other, so that it may be less 

 heated when the temjierature of the platina ring is raised to red heat. On 

 the contrary', if we place the focal heat on the side of the copper wire, 

 the electrical effects are reversed; and if we substitute in place of the 

 platina wire another copper wire, the electrical effects will still be the 

 same. But exposing the two rings to the same temperature, there will be 

 no effect produced. The layer of sulphur with which the copper ring 

 is covered sensibly augments the intensity of the current. 



Here then are two distinct electrical effects in a closed circuit, con- 

 sisting of vires of two different metals, according as those vvires are 



• S of a millimetre is about ,\ of an inch ; 3 iiiillinietrcs is about l of an inch. 



