Mr, J. Prideaux on the Theory of Voltaic Action, 257 



for twenty-four hours in the air gave only 35° 9 but steady. 

 Hence some accumulation seems to take place in the air 

 during the drying of" the plates, perhaps communicated by 

 the vapour. 



39. These experiments go in confirmation of the supposition 

 (35), that the electric attraction, arranging the negative parti- 

 cles of the liquid against the face of the positive metal, and 

 vice versa, and thus tending to saturate itself, should gradually 

 extinguish its own action. 



And from previous observations (14, 15, 19, 22,) it might 

 be inferred, that the destruction of zinc by acid charges is 

 waste. 



Entire extinction of the electromotion by saturation is, how- 

 ever, prevented by the unsteadiness of liquid particles ; and 

 by the imperfection of liquid conducting power, whatever its 

 mode of action, obstructing the effects on the particles not in 

 immediate contact with the metals; which are sufficient to 

 keep some action alive for a good while, where only neutral 

 charges are employed. But when free acids are used, which 

 dissolve the zinc, a more powerful compensating force comes 

 into play. 



Sect. VI. Of the Effects of Chemical Action. 



40. It has long been shown by Becquerel*, that when a 

 metal is acted on by an acid, and forms with it an oxide or a 

 salt, the metal becomes negatively, the liquid positively, elec- 

 tric ; and accordingly it is familiar to Voltaists, that when, 

 into an acid liquid, two plates of zinc are plunged, the one 

 new and bright, the other corroded, connexion being made 

 through a multiplier, the corroded plate is positive (in the 

 liquor) to the bright one. 



41. It has also been shown by Sturgeon, and had been shown 

 before him by Davy, that if two plates of iron with bright sur- 

 faces be plunged into dilute muriatic acid, and after a time 

 one of them be withdrawn, and kept for some seconds out of 

 the acid, on being replaced it acts as copper ; and so alternately 

 either plate withdrawn for a few seconds, acts as copper on 

 reentering the liquor. And the case is the same with zinc, as 

 any one possessing a couple of zinc plates may prove in a 

 minute. 



42. These two experiments (40, 41), and BecquerePs ge- 

 neral principle (40) explain each other. When bright and 

 corroded zinc are brought into contact with an acid, the latter 

 yields most readily to its action, and gives off electricity to the 

 liquid, which returns through the bright plate and the wire. 



* Ann. de Chim. ct de Phys. May 1829. 

 Third Series. Vol. 2. No. 10. April 1833. 2 L 



