Chemical Science. 383 



little sulphuric acid is present, and the iron and zinc are acted 

 upon ; so that chemical action in this case did not prevent the 

 production of electricity by the contact of metals and water. 



By certain changes of the surface, it was found that the intensity 

 of electricity produced was much affected. A plate of gold, 

 plunged in nitric acid for a few moments, and then washed in several 

 fresh portions of water, produced a developement of electricity 

 much greater than before, the water still becoming negative. The 

 same plate, plun^fi into a solution of potash and then washed, 

 lost in a great measure its power of becoming electrified by con- 

 tact with water. A plate of platinum offered similar results. It 

 is supposed, that these effects may have a distant analogy with the 

 facts observed by M. M. Thenard and Dulong, that a new platina 

 wire, which would not heat in a current of hydrogen gas and air, 

 acquired this property by being previously plunged for a few 

 minutes in nitric acid, and then washed. The property of the wire 

 continued for above twenty-four hours ; and M. Becquerel says, 

 that the plate of gold preserved its power of becoming strongly 

 electrified in contact with water, for several hours. — Ann. de Chim. 

 xxvii. 5. (See the phenomena described by M. Yelin. Quarterly 

 Journal, v. p. 170.) 



3. On the Electrical Actions produced by the Contact of Flames 

 and Metals. By RI. Becquerel.— In place of making a complete 

 metallic circuit, as in Seebeck's experiment ; or one in which the 

 circuit was by water or acid, as in the voltaic pile ; the metals used 

 were connected by a flame only, and their states ascertained by the 

 electrometer. The flames used were those resulting from the com- 

 bustion of alcohol, hydrogen gas, or a sheet of paper. When a 

 plate of platina was placed on the cap of the electrometer, and 

 heated by one of the flames before mentioned, if the tempera- 

 ture was a red heat or above, the metal became negative, but 

 below a red heat it became positive. On trying the electricity of 

 the flame, by making it rise from a piece of wet wood on the cap 

 of the instrument, and holding the platina in it, the reverse, as 

 expected, was found to be the case. 



A copper wire gave the same results, and generally it appeared 

 that all the metals had the property just described ; thus any metal, 

 plunged into a flame of hydrogen gas, becomes negative or positive 

 according as the temperature is higher or lower, and communicates 

 the contrary electricity to the flame. 



If the flame by which the plate of metal on the cap of the in- 

 strument is heated, be touched by a piece of wet wood instead of 

 being insulated, the effects are more distinct : but if instead of 

 touching it with wet wood, it be touched with :i plate of the same 

 metal as that on the electrometer, the two portions of metal are 

 found in did'erent states : that healed to redness bein;^ negative, 



