yer, Scant ge for thesé five classes of bodies: 
ist, Insu 3 2d, Perfect conductors ; 3d, Bi im- 
perfect conductors; 4th, Positive unipolar; and 5th, Ne- 
nti unipolar: tes Phys. \xiv. 121.) Although, as we 
] afterwards find, Mr le explains the facts upon 
rather a different principle, yet they are highly impor- 
tant, and M. Erman is entitled to much commendation 
for the skill with which he conducted his experiments. 
ns ie heap Suggested an idea, which appears sufficiently 
tions plausible, that the action of galvanism may affect the 
i Sindsoaten of metallic oxides, and even cause them to 
assume the particular forms which they occasionally ex« 
holtz hibit: (Ann. de Chim. Ixiii. 113.) Bucholtz detailed a se- 
reducing ries of experiments which he performed, where a me- 
“ tallie oxide, held in solution by an acid, was precipi- 
tated in the metallic state by the metal itself. The me- 
tallic solution was placed in the bottom of a cylindrical 
jar, and a stratum of water was carefully spread over 
it. A slip of the same kind of metal that formed the 
solution was then ed 
pedi 
meus’s per of the . Experiments of an analogous 
ws Hogohall performed by Grotthus, on what he calls 
the arborization of metals, which, like the circle of 
actions described by Bucholtz, he attributes to a gal- 
vanic operation. In these processes, however, there 
are two metals concerned ; and he shews that the tree 
is formed by oy pete ee of the dissolved oxide 
being reduced and a’ to the solid metal, which, 
im its turn, becomes oxidated: (Ann. de Chim. Ixiii. 5.) 
We have a little anticipated the chronological order in 
the relation of these two last sets of experiments, in 
order that we might not be interrupted in narrating the 
account of the decomposition of the alkalies and earths, 
which composes the third period of the history of gal- 
yanism., 
Szcr. HI. Decomposition of the Alkalies and Earths. 
's About the conclusion of the year 1806, Sir H. Da 
etro-che- read to the Royal Soeiety of London the first of his 
Hic series of papers, on what has been styled the electro- 
chemical action of bodies, which have been so justly 
celebrated, no less for the brilliant discoveries of which 
they give an account, than for the acuteness and saga- 
‘city which the author displays in his researches into 
tion of the most hidden operations of nature. He commences 
icity by some remarks on the action of galvanic sete 
on water, upon water. He notices the experiments in whic 
acids and alkalies appear to have been formed in water 
subjected to the galvanie current; and he states, that 
“when he emp] separate portions of water, connected 
together by slips of bladder, and united by gold wires 
to the voltaic battery, he obtained nitro-muriatic acid 
at the positive, and soda at the negative wire. It was, 
however, conjectured, that the animal matter placed 
between the two portions of water might contain mu- 
‘riate of soda, and thus afford the substances procured 
in the experiment; he therefore, at the suggestion of 
Dr Wollaston, substituted asbestos for the slips of 
‘bladder: It was also conceived, that when glass ves- 
Ne ‘sels were used, the alkali might proceed from a partial 
CB it, decomposition of the glass; wet after trying various 
‘ig. 8 other substances, at length conical vessels of gold were 
VOL, X. PART 1 
GALVANISM. 
complished ; and w 
89 
employed, With these precautions, and when the water History. 
was very carefully prepared, no acid or alkali were ob. "-y—— 
tained ; and consequently thé author concludes, that in No acid and 
all those experiments which were attended with con- alkali gene- 
trary results, the acid and alkali must have proceeded tated, 
from some extraneous source, not having been e- 
rated, but evolved, either from something held in so- 
Lore by ee water, or from some of the materials em- 
ployed in the apparatus. Perfect} water, when 
subjected to the action of electricny, of affords nothing 
except oxygen and hydrogen. 
The very powerful action of jek aapeery electricity, Decomposi- 
in the decomposition of various earthy and saline com- caetin al 
pounds, as experienced by Sir H. Davy in the researches part 
above mentioned, offered an extensive field for farther salts. 
investigation. Hisinger and Berzelius, in the valuable 
memoir to which we have already referred, noticed the 
tendency which different bodies possess, to attach them- 
selves to one of the wires exclusively ; acids and analo« 
bodies being attracted to the positive, while alka- 
es, metals, and all inflammables, were attracted to the 
negative wire. Our author had observed similar pheno- 
mena in his own experiments, and was induced to make 
them the more immiediate subject of his examination. 
Acids and alkalies were found uniformly to observe this 
order ; and it was perceived, that when substances, not 
supposed to be soluble in water, formed part of the 
circuit, they were also decomposed, and their compo- 
nents carried to the positive and negative wires respec- 
tively. In this way was effected the decomposition of 
—y e of lime, sulphate of strontites, fluate of lime, 
sulphate of barytes. It was also perceived, that 
where small portions of acid and alkaline bodies entered 
into the composition of solid earths, they might be de- 
tected by the galvanic influence, and would be trans- 
mitted to their respective wires. In this way, lime and 
soda were obtained from basalt and from zeolite, 
ash from lepidolite, &c. In proportion to the solubility 
of a salt, its decomposition was the more readily ac- 
a8 neutral salts were employed, 
the separation of the component parts seems to have 
been quite complete. 
The tendency which different substances possess to Transfer of 
attach themselves to their appropriate wires, causes the consti- 
them to be transferred across a medium which may be tuents of 
interposed. Thus, if muriate of lime be at the positive C°™Ppounds. 
wire, the lime will pass, for a considerable space, to PLATE 
-gain the negative wire, and may be conveyed from one CCLXUI. 
vessel to another along the conducting fibres of the as- 
bestos. In the same manner, when nitrate of silver 
was on the positive side, and distilled water on the ne- 
gative, the silver passed along the transmitting ami- 
Figs, 10, 
il. 
-anthus, so as to cover it with a thin metallic film. When 
a neutral salt was placed in a vessel, between two other 
vessels of water connected by asbestos, the alkali pass- 
ed to the negative, and the acid to the positive side : 
the decomposition in this case is complete, and the sub- 
stances produced quite pure. A small vessel of the in« 
fusion of litmus was in between pure water 
and the solution of sulphate of potash, and the latter 
was negatively electrified. The acid across to 
the positive wire, and reddened the litmus, but the 
change of colour did not extend beyond the centre ; so 
that the negative side, although it was transmitting the 
acid, was not affected by it. An experiment of pre- 
cisely an opposite kind was performed with the infu- 
sion of turmeric, with a similar result ; and afterwards 
the two operations were combined’ in the same experi~ 
ment, sothat soda passed through turmeric, and muri- 
™M 
