170: Miscellaneous Intelligence. 



A plate of copper, or zinc, in place of the gold, yields sirtiilar 

 results without the aid of the muriatic acid, and although some- 

 times the current changes its direction without any apparent 

 reason, yet, generally, when an acid acts on an alkali or a metal, 

 the acid takes the positive electricity, and the alkali or metal, 

 the negative. 



M. Becquerel remarks, that there are so many different chemical 

 phenomena occurring when an acid acts on a metal, all ol which have 

 their respective power of exciting electricity, that it is no wonder 

 anomalies sometimes occur; and he found he was able to remove 

 some of these, even by the comparatively coarse precaution, of 

 shielding the platina part of the galvanometer wire from particles 

 which the chemical action might throw on to it ; and by allowing 

 time for the cessation of capillary action, and the removal of sub- 

 stances acted upon by the acid, from the surface of the plates or 

 from the paper. 



The question then occurred whether the heat produced by the 

 chemical action, was, or was not, the cause of the electrical current. 

 To ascertain this with regard to the action of an acid on copper, 

 instead of using a plate of the metal, it was made into a small 

 cylinder which was filled either with a coagulated fatty substance 

 that would easily fuse, or with ice. It was considered that any 

 free heat produced by chemical action would be employed in 

 melting the enclosed substance, and therefore removed as fast as 

 produced, but the effect was the same as before. Again, one end 

 of the galvanometer wire was terminated by a platina vessel con- 

 taining an alkalme solution, the other platina extremity, introdiiced 

 at the same temperature, produced no electrical current; but when 

 previously heated and then introduced, a current was produced ; 

 the positive electricity being produced by the heated side, and thd 

 negative electricity by the other. But in the experiment with 

 copper in nitric acid, the current was in the opposite direction, 

 and therefore could not have been due to any heat produced by 

 chemical action. 



The preceding electrical effects relate to currents, and M. Bec- 

 querel states, he was unable, even by the aid of his very sensible 

 electrometer*, to detect electricity of any tension due to the action 

 of nitric acid on copper, or of dilute sulphuric acid on zinc. The 

 experiments, however, with the galvanometer have proved that 

 when acids and alkalies combine, the acids take the positive elec- 

 tricity, and the alkalies the negative ; whilst, by the electroscope, it 

 was shewn that on contact only, without chemical action, the acids 

 take the negative electricity and the bases the positive ; a very 

 remarkable distinction between the electrical effects due to che- 

 mical action, and those due to contact. 



* Quarterly Journal, xvii. 374. 



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