116 On some Chemlcat Agciicks of FilectrkUy i 



ceedinglv sensible electricities, which require for their exbiJ 

 bition tlie gold leaf electrometer only with the small con- 

 clensiniT plate. 



When oxalic, succinic, benzoic or boracic aciJ, per- 

 fectly dry, either in powder or crystals, were touched upon 

 an extended surface with a plate of copper insulated by a 

 glass handle, the copper was found positive, the acid nega- 

 tive. \n favourable weather, and wlicn the electrometer was 

 in perfect condition, one contact of the metal was sufficient 

 to produce a sensible charge; but seldom more than five 

 or six were required. Oilier metals, zilic and tin for in- 

 stance, were tried with the same effect. And the metal re- 

 ceived the positive 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 

 miited, 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 exceedingly distinct, a single contact upon a large sur- 

 face 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 Jays in 

 glass bottles before they vvere used : it is essential to the suc- 

 cess of the process that thev be of the temperature of the at- 

 mosphere. In some experiments which I made upon them 

 Avhcn cooling, after having been ignited, they appeared 

 stronuily electrical, and rendered the conductors brought in 

 contact with them positive. 



I made several experiments, in a similar manner, on (her 

 effects of the contact of potash and soda with the metals. 

 Potash in no instance afforded a satisfactory result ; its pow- 

 erful attraction for water presents an obstacle probably un- 

 surmountable to the success of any trials made in the free 

 atmosphere. Soda, in the only case in which electricity 

 was exhibited, affected the metal in the same way as linjey 

 ' . strontites. 



