Mr. J. Prideaux on the Theory of Voltaic Action. 219 



portions,) whether water, a saline solution, or an acid was em- 

 ployed. 



But on soaking the paper in a strong alkaline solution (liquor 

 potassae), the rate was inverted, and the maximum effect pro- 

 duced when the liquid was in full contact with the zinc. 



Alcohol produced, as might be expected, no effect whatever. 



In these experiments, the effect of the copper is weakened 

 by the liquid in contact with it being electro-positive (alkaline), 

 and destroyed by the interposition of a ring of positive metal 

 (zinc) between it and the liquid. And the effect of the zinc is 

 reduced by negative character in the liquid with which it is 

 in contact, or annulled by the interposition of a ring of nega- 

 tive metal between it and the liquid. 



20. This similar effect of homo-electric metals and liquids, 

 and vice versa, in their contact with the voltaic plates, seems 

 to offer a clue to the theory of the cases, (9, 13, 14, 15, 45,) 

 and of other unexplained phenomena of the pile. If a nega- 

 tive metal, placed between the zinc and the liquid, neutralizes 

 the effect of the silver on the other side, has not a negative 

 property in the liquid itself a similar tendency ? — modified and 

 impaired, of course, by the mobility and unsteadiness of liquid 

 particles. 



If it be so, when a negative liquid is in contact with the 

 zinc of a voltaic pair, the effect should be (except chemical 

 action, 40.) the difference between the influence of the negative 

 metal and the negative liquid. On the other hand, when the 

 negative liquid is in contact with the copper, the effect should 

 be, the influence of the zinc, plus that of the negative liquid* 

 And if we possessed a liquid of good conducting power, which 

 should be electro-positive to zinc, the condition of that metal 

 might be likewise exalted. But here we are restrained by 

 the non-conducting power of oils, naphtha, alcohol and the 

 like ; and as water is negative to zinc, and alkaline solutions 

 seem to lose in conducting power faster than they gain in 

 electro-positive condition, a solution of neutral salt slightly alka- 

 lized seems to answer the best purpose with this metal: for — 



21. In experiment (14.) when the alkaline liquid contained 

 a double quantity of potass, and was poured in nearly an inch 

 deep, the effect was remarkably weakened, the deflection of 

 the needle not exceeding 10° or 12°; and very little oxide 

 formed on the zinc, or hydrogen on the copper. But — 



22. When the liquid was of the strength given (14, note) 

 and only \ inch deep, — as the zinc became coated with gela- 

 tinous white oxide, so the alkaline stratum was gradually be- 

 coming shallower, by the electrical current carrying it up into 

 the acid ; and thus what was lost in conducting power by the 



2 F2 



