“96 
History. atie acid through litmus, each without changing their 
—Y— colour. 
Passage of As it appeared that acids and alkalies could be ‘con- 
acids and yeyed through water, without affecting colouring sub- 
Wkalies ig, Stanees dissolved in it, Sir H. Davy next tried whether 
forent me. this power might not extend to other bodies. He ac- 
dia, cordingly found, that acids could be transmitted through 
alkalies, and alkalies through acids, to their respective 
wires, without neutralizing each other ; and, ‘in short; 
that the electrical state which was induced upon a sub- 
stance, by the contact of the galvanic apparatus, had the 
- power of ‘counteracting, or even changing, the effects 
General _ of chemical affinity. The general principle was thus 
principle.“ eompletely established, that hydrogen, alkalies, and 
metals, are attracted by the negative, and repelled by 
the positive end of the pile, while acids and oxygen are 
attracted by the positive, and repelled by the negative. 
For the production of this effect, it is necessary that 
there be a conducting chain of particles through the 
transmitting fluids; the transfer cannot take place 
where insoluble compounds are formed, because in this 
case the new compound is carried out of the sphere of 
action, ; 
Effect of The establishment of the general principle mentioned 
spate above, suggested some views of the nature of the change 
inp chemi. Produced by electricity, which led to a new train of 
cal changes, €Xperiments. Sir H.' Davy. observes, that many bodies, 
after being brought into contact, exhibit opposite states 
when they are separated. When a galvanic combina- 
tion is formed from an acid, an alkali, and a metal, the 
alkali appears to acquire, and the acid to part with, a 
quantity of electricity; the alkali is therefore rendered 
positive, and the acid negative, and they will of course 
have anattraction for each other. He found, that when 
such acids as were capable of being employed in the 
dry state were touched by metals, and then separated, 
the acids were rendered negative, and the metals posi- 
‘tive ; but: when the metals were touched by the alka- 
line earths, the metals became negative. Hence itma 
be concluded, that acids and alkalies not only exhibit 
~pposite electricities, when they have been in contact 
with metals, but also when they have been in contact 
‘with each other. |Thevattraction of oxygen and acid 
for the positive, and of hydrogen. and alkalies for the 
negative electricity, is so powerful, as to counteract 
their usual chemical affinities. 
— be- sa eee induced the author to enter into 
ween the some farther speculations respecting the relation be- 
od affinity tween the electricity of nitedens these chemical affini- 
of bodies. ties. We have seen that chemical affinity is destroyed 
-by giving a body an electricity different from its natural 
-one, and is, on the contrary, increased by giving it a 
greater “share of its natural electricity. Jt would far- 
ther appear, that all those bodies which possess a che- 
mical affinity for each other are naturally in opposite 
states of electricity, and hence we conclude, that by in- 
‘ducing a state of electricity upon any body, contrary to 
its natural one, its chemical relations may be changed, 
and that thus we have in our’possession an agent of in- 
definite power for affecting the decomposition of sub- 
stances which had hitherto withstood all our attempts. 
eager of «With respect to the action of the voltaic pile, Sir H. 
an Davy conceives; that the first step in the process is the 
destruction of ‘the electrical equilibrium, and that the 
chemical changes tend _to restore it to its original state. 
The saline solution, which is interposed between each 
_ Pair of plates, is decomposed, the acid is transferred to 
the zinc, and the alkali to the-copper surface. This 
tends to restore the equilibrium, which is destroyed by 
GALVANISM. | 
4 
the contact of the metallic elements ‘of the pile; but the History 
solution of the zine, which then takes place, again alters 
the electrical condition of the bodies, and maintains the = 
energy ofthe apparatus. Upon the whole, although it Primary 
ry be supposed that the chemical are an es- fects 
sétitial pact the process, they are considered by the ‘tea 
author as only of secondary importance; the first step 
in the process, and that which immediately gives rise 
to all the rest; being an electrical effect arising from the ; 
action of bodies placed in contact. F 
The uncommon merit of this paper has induced us Importani 
to give a-copious abstract of its contents. It may be re- of this pa 
garded, not only as giving rise to some of the most ims Pe. 
rtant experiments and discoveries that have occurred » 
in the history of modern science; but/as leading to the © 
establishment of a new train of reasoning, and to anew aig 
theory, respecting the action of bodies upon each other, . 
and the connexion which subsists between the. diffe- 
rent branches of natural philosophy. The general prin- 
ciple being clearly established, the consequences were 
comparatively obvious, and the skill and ingenuity, 
which Sir H. Davy afterwards manifested, in the con- 
trivance and execution of the experiments, which are 
next to be related, although attended by such brilliant 
results, are really less meritorious, than that profound 
insight into the operations of nature, by which they 
were suggested. Highly, however, as we appreciate 
the merit of Sir H. Davy, we think it proper to remark, 
that the views suggested by Hisinger and Berzelius 
must be regarded as leading to the theory that was so _ 
amply detailed and so firmly established by our. illus- 
trious countryman. | See Phil. Trans. for 1807, 1. - 
About a year after the reading of the above paper, Decompe 
Sir H. Davy presented a second to the Royal Society, in tion of 
which he most happily applied his hypothesis to prac- ai 
tice, and Rp HB in solving the problem, which had “** 
so long remained involved in obscurity, respecting the . 
composition of the fixed alkalies, After encountering . 
some difficulties in the arrangements of the operation, 
the grand object was at length accomplished in the fol- re 
ment. 
a. re 
lowing manner. “ A small piece of pure potash, which 
had been exposed for a few seconds to the atmosphere, 
so as to give conducting power to the surface, was 
placed upon an insulated disc of platina, connected with 
the negative side of the battery, of the power of 250 of 
6 and 4, ina state of intense activity; and a platina 
wire, communicating with the positive side, was prone 
into contact with the upper surface of the alkali. e 
whole apparatus was in the open atmosphere. Under 
these circumstances, a vivid action was soon observed 
to take place. The potash began to fuse at both its 
points of electrization, There was a violent efferves- 
cence at the upper surface ; at the lower, or n ive # 
surface, thete was no liberation of elastic fluid; but 
smail globules, having a high metallic lustre, and being 
precisely similar in visible characters to quicksilver, ay 
peared, some of which burst with explosion and bright 
flame, as soon as they were formed, and others remain- 
ed, .and were merely tarnished, and finally covered by 
a white film, which formed on their surfaces.” 7 - 
These globules proved to be the substance of which Base of 
the author was in search, and were found to be a pecu- *sh and 
liar inflammable body, possessed of very singular pro- ¢' 
perties, which constituted the base of potash. By em- 
ploying a similar kind of process, a substance was pro- 
cured from soda; which exhibited properties of an ana- 
logous nature, and which was the basis of the mineral, 
as the former was that of the vegetable alkali. me ele 
The author then proceeded to examine the properties be m 
3 
