46 *W SOME CHEMtCAt AGENCIES OF ELECTRIC! TT. 



Genera! prin- effects Were unsatisfactory, the circumstances of evaporal ium' s 



chemteal ' anr * °^ chewed action, and the adherence of the solutions 



cha up ■> pro- to the surfaces of the metals employed, in most cast's, piv- 



>;. e ee- ven ^ e( ] an y distinct result, or rendered the source oi* tin 



tiieity doubtful. I shall not enter into any details of these 

 processes, or attempt to draw conclusions from capricious 

 and uncertain appearances, which, as we shall immediately 

 see, may be fully deduced from clear and distinct ones. 



The alkaline and acid substances capable of existing in the 

 dry and solid form, give by contact with the metals exceed- 

 ingly sensible electricities, which require lor their exhibition 

 the gold leaf electrometer only with the small condensing 

 plate. 



When oxalic, succinic, benzoic, or boracic acid, perfectly 

 dry, either in powder or crystals, was touched upon an ex- 

 tended surface with a plate of copper insulated by a glass 

 handle, the copper was found positive, the acid negative. In 

 favourable weather, and when the electrometer was in pet- 

 feet condition, one contact of the metal was sufficient to pro- 

 duce a sensible charge; but seldom more than five or six 

 were required. Other metals, zinc and tin for instance, were 

 tried with the same effect. And the metal received the posi- 

 tive charge, apparently to the same extent, whether the acid 

 was insulated upon glass, or connected with the ground. 



The solid acid of phosphorus, which had been strongly 

 ignited, and most carefully excluded from the contact of air, 

 rendered the insulated plate of zinc positive by four con- 

 tacts; but after exposure to the atmosphere for a few mi- 

 nutes it wholly lost this power. 



When metallic plates were made to touch dry lime, stron- 

 tites, or magnesia, the metal became negative; the effect was 

 exceedinglv distinct, a single contact upon a large surface 

 being sufficient to communicate a considerable charge. For 

 these experiments the earths were carefully prepared; they 

 were in powder, and had been kept for several da^s in glass 1 

 bottles before they were used : it is essential to the success of 

 the process that they be of the? temperature of the atmos- 

 phere. In some experiments which 1 made upon them when 

 cooling, after having been ignited; they appeared strongly 



electrical, 



