Chemical Science. 375 
- In general metal in contact with acid becomes positive, making 
the acid negative, and with alkalies the reverse effects are obtained ; 
but there are many cases, as with silver, in which the electro- 
motive action can scarcely be observed. 
“ Sir H. Davy had found that those acid and alkaline substances 
which can exist in a dry and solid form become electrical by their 
contact with metals; thus perfectly dry oxalic or succinic acid, either 
in powder or mass, when placed on a copperplate, takes negative 
electricity, and communicates positive electricity to the metal. The 
celebrated English chemist found also, that in consequence of the 
difficulty of depriving potash and soda of water, they did not in 
general produce any electricity by their contact, but that after being 
strongly calcined they possessed for a moment the power of be- 
coming electric by contact with a metal, He endeavoured also to 
determine, by means of very delicate instruments, the electric state 
of an insulated acid or alkaline solution after their contact with the 
metal, but there were no results of that nature.” ; 
“« We have proved, therefore, that the electric effects observed by 
Sir H. Davy as produced by the contact of a solid dry acid or alkali 
with a metal, and where consequently there is no chemical action 
extends to the contact of all the metals with acid or alkaline solu- 
tions, even though sometimes chemical action may have com- 
menced.” 
Haying determined the electric state of an acid or alkaline solu- 
tion in contact with a metal, the next object was to ascertain the 
effect when the solution was placed between two different metals, 
The copper capsule was placed on the upper condensing plate, and 
filled with an alkaline solution or very dilute sulphuric acid; the 
solution was then touched by a plate of zinc, taking care that the 
two metals did not come in contact, and the lower condensing plate 
was touched with the finger; twenty seconds after, on raising the 
upper plate the gold leaf moved towards the positive pole, so that 
the copper capsule had become positively electrified. On putting a 
zinc capsule on the upper plate with one of the two solutions, touch- 
ing the lower plate with a piece of zinc so as to neutralize the electro- 
motive action of that metal on the copper, and touching the liquid 
with a piece of copper held in the hand, an electrical state was pro- 
duced, which, on raising the upper condensing plate, made the 
gold leaf move towards the negative pole, consequently the zinc 
capsule had become negative. Hence it is seen, that when zinc and 
copper are separated by an acid or alkaline solution, the zinc becomes 
negative, and the copper positive, which is the inverse of that which 
takes place when the two metals are in contact. 
Another result obtained experimentally by M. Becquerel is, that 
copper in a solution of muriate of soda becomes negative, and the 
solution positive. —Ann. de Chim. xxv. 405. 
