136 Progress of Foreign Scvence. 
electricity ill, there is no current, although the chemical action be 
very strong. The conductibility then is here an indispensable con- 
dition. ‘ef 
We shall examine in succession the electrical effects that we 
have observed in different chemical actions by the aid of the multi-. 
plier ; 72z.—1, At the moment of the combination of acids with 
metals and alkalis.’ 2. In the dissolutions. 3. In the contact of 
metallic oxides with the alkalis which combine with them. 4. In 
the precipitates. As to double decompositions, it has been im- 
possible for me to recognise the slightest trace of electricity at the 
moment of their formation. 
Electrical Effects produced at ihe moment of the Combination of the 
Metals and Alkalis with the Acids. 
We have seen above that Sir H. Davy observed electrical effects 
on the contact of acids and alkalis, only when these bodies had 
been perfectly dried. M. Cérsted asserts that he has perceived 
them at the instant when the acid combines with the metal. 
‘The following is the means which I employ to shew the elec- 
trical effects in these species of actions. I make use of a galva- 
nometer, whose wire is of platinum. (See p. 124 of this volume.) 
At one of the extremities of this wire I placed a little platinum 
spoon destined to receive the acid, which is selected of such a 
nature as not to act on the platinum. To the other end of the 
wire is adapted a piece of the same metal, between the branches of. 
which (as pincers) the body is placed, which is to act on the acid. 
In case the platinum could exert an electro-motive action on this 
body, there is placed between them a bit of moistened paper. Let 
us begin by shewing what electrical effects result at different tem- 
peratures from the contact of a liquid with the platinum. At 
the ordinary temperature, whatever be the liquid, provided it is 
not nitro-muriatic acid, the electrical current is null, but when the 
temperature is raised, phenomena occur which we shall endeavour 
to explain. Let us put into the spoon distilled water, and let us 
raise the temperature to ebullition, there will be no current in con- 
sequence; if the water of the Seine be used, the current will be 
extremely feeble, and it will increase in intensity by the addition 
of a little nitric acid, or alkali. Now, since we know that boiling 
nitric acid has no more action on platinum than cold nitric acid, it 
is hence probable that the current is owing to the difference of 
temperature of the two ends of the wire. It has been already 
shewn in a former memoir that two pieces of the same metal, in a 
sufficiently unequal state of temperature, pass, on their mutual 
contact, into two different electrical states. This change of tem- 
perature must therefore be avoided, which is done by using small 
