GALVANISM. 
only be faid to keep up the es énergy, and ‘therefore 
the firft effe& alan ut be 1e fam cua ie ontrary: 1 
to the fac. A 
oyed. Asa pr 
if the trough be fhaken, fo as to mix the different fubftances 
in the cells, the power becomes much revived. Several 
affertions here are not fupported by fact, In the firft place 
no faline folution, even in the firft beginning, produces fo 
great an-effect as a free acid, diluted with water, particu- 
larly the nitric ‘a 
r. Dav aa account for the great effect of the nitric 
acid fon the acid undergoing decompofition. From fimilar 
reafonings nitrat of potafh fhould produce the greateft 
effe poffible, becaufe both the falt and the acid are decom. 
pofed. This, however, does not agree with experience, 
nee muriat of foda produces a greater effe& than nitrat o 
although the rae pire with Mr. Davy 
hy pot fhould produce a greater effect than nitric acid, 
by the additional eleétrical 5 aa ‘f the acid ‘and th 
alkali. 
~ 
a 
With refpeé to the permanence of the effeG, it will be 
found in practice that acids which produce the greateft effe€t meta 
rit Haw are the lea a and that faline 
upon zinc very flowly, air und to be 
m : *Thofe falts wil be ne dm 
which on triple falts with z He why 
muriat of foda acts more powerfully than nitrat of potafh, 
and why muriat of ammonia is ftill more energetic than 
muriat of foda, fince it oxydates, and combines with metals 
ere are other facts which mili- 
a gre 
A folution of cauftic of tray is 
odies ern 
Davy, inthe paper to which we have before alluded: ee a 
that if electricity were produced during chemical changes, 
it ought to be appreciated by the eleCtrometer ; but till we 
are better acquainted with the connection between electricity 
and caloric, the latter of which is always difturbed durin 
chemical aac nothing conclufive can be drawn hee fuck in 
effe nic combination of zinc, 
copper, and nitric acid, the zinc is is pofitive . Buton a com- 
bination of zinc, nitric and. and water, the fide of the zinc 
next the acid is negative. If, he obferves, the Galvanic 
effect was dependent on the chemical a the zuic would 
be f fitive in eee in ances. That the zinc in contact 
offed is not refult of the che cal 
mt 
n all cafes i 
- of cleétricity. 
e which the limbs are placed, at the fame time e that t 
aes wn experiments t 
— nia —No fubfiance ean poflibly enter 
o any Galvanic combination jaan i bs a ae condu€tor 
"Phe moft common mple Galvanic 
combination confitts of. two furfaces of itil metals and 
a fluid containing oxygen placed between them. One o 
the metals fhould be fufceptible of Sahon by the fluid, 
and the other lefs fufceptible of oxydation by the fluid, A 
made en : e two metallic furfaces, 
either re bringing the metals together, or by eters 
ica by a metallic fubftance, will fhew the effe@& of t 
combination by fuch tefts as will hereafter be Sehey 
alvanic combination, as Mr. Davy has thewn, may be 
formed of one metal only, by its being fo fituated that one 
feats teft of any Galvanic combination is the mufcles of a 
recently killed frog: if the limbs are placed in the circuit, 
which connects the two metallic furfaces, at the fame time 
in any degree 
art is 
moiftened with water, convulfions will be eenernirel as often: 
as a metallic communication is made between the diffimilar 
Is. = the tongue be made to touch the two metals 
a Galvanic combination, at the fame: time that 
and if th 
diffimilar, fuch for inftance as filver and zinc, at the mome 
of contact, a flafh of light will be perceived ‘nile to that: 
produced by a blow about the eye. In {peaking of Galvanic: 
combinations in future, we ‘hall call that metallic furface 
which is undergoing oxydation the pofitive furface; the: 
Gihee metal, which mutt be lefs fufceptible of oxydation, we- 
fhall denominate the negative furface; and the oxydating” 
medium, the interpofed fluid. 
ertaining the power of any Galvanic combination: 
all make ule of a teft different from either of thofé 
aia hihaase ei fince it will be found more convenient and’ 
was difcovered by Dr. Wollafton, as we have 
regular. 
t be i re flat ed, that in peel Galvanic combination, the nega-. 
€ circuit is complete, is obferved to 
to be h ydrogen, roa 
- fetes fo lon 
out bubbles of bon pera is found 
Fhat this gas ceafes to be evolved as fo 
parated. The moft coment way of making thefe exper 
ments, is with wires of the metals: the fluid i in which the: 
wires are fir _ 
"2 
hie 
QB 
cg. 
Q 
° 
tae] 
y 
faery 
og 
> 
= 
RR 
mie 
(o) 
gp 
Q 
me 
pP. 
tie rie 
Seg wire, if of ‘patna mold. filver, copper, or brafs,. 
will not exhibit a ange. however, the ends of the. 
wires out of the liquid be tea into contact, an abundance 
wire. Zinc, with 
The aa um is made io at and a quantity of bub-- 
Hee hich could juft be defcried. by a magnifying glafs, is. 
called 1 
Pofitive. 
