LONG-CONTINUED ELECTRIC CURRENTS OF LOW TENSION. 
41 
«ork fixed in the mouth of the smaller tube, and dips into the metallic solution it 
contains. 
8. When a solution of the chlorides or nitrates of iron, copper, tin, zinc, bismuth, 
antimony, lead, or silver, is placed in the smaller tube of the apparatus (7.), and con- 
nexion made with the battery* in the manner already described, action is almost 
instantly apparent, water is decomposed, and torrents of minute bubbles of hydrogen 
are evolved at the surface of the platinum plate, (negative electrode,) which continues 
for a short time, sometimes, indeed, lasting for hours ; a circumstance depending 
apparently upon the degree of facility with which the metal under experiment is 
reduced. Thus with solutions of copper, scarcely a bubble appears, the metal being 
almost immediately reduced, all the hydrogen being probably employed from the 
instant of completing the circle, for that purpose: with solutions of lead, tin, or 
silver, the evolution of hydrogen continues for a short time only, and ceases as soon 
as the minutest portion of reduced metal appears on the platinum plate ; but with 
solutions of iron and manganese the evolution of gas frequently continues for six, 
eight, or ten hours, or even longer ; the evolution of hydrogen thus seeming to bear 
something like an inverse ratio to the ease with which metal is reduced. After the 
hydrogen has ceased to appear at the negative electrode, striae of the reduced metal, 
which rapidly increase, are deposited on the surface of the platinum. 
9. The metals thus reduced generally, but not invariably possess a perfectly me- 
tallic lustre, are always more or less crystalline, and often very beautifully so, af- 
fording a considerable contrast to the irregular soft spongy masses obtained from the 
same solutions by means of large batteries. The crystals of copper obtained by the 
process just detailed (8.), rival in hardness and malleability the finest specimens of 
native copper, which they much resemble in appearance. The crystallization of bis- 
muth, lead, and silver by these means, is very beautiful, that of the former metal 
being lamellar, of a lustre approaching to that of iron, but with the reddish tint pe- 
culiar to this metal. Silver may be thus obtained of a snowy and indeed dazzling 
whiteness, usually under the form of needles. 
10. The metallic solutions hitherto mentioned as yielding to the action of the little 
battery are, as is well known, equally acted on by larger voltaic batteries, consisting 
of a considerable number of alternations, the metal being reduced in a spongy form, 
often destitute of a metallic appearance. But there are some metals which are de- 
posited from their solutions as oxides only, when acted on by currents from large 
batteries, and yet are deposited in a brilliant metallic form if submitted to the action 
of the currents from the little apparatus already described (4). Of these nickel is 
an example : a solution of its chloride or sulphate, when placed in the smaller tube 
of the decomposing apparatus (7.)> yielding after some hours a crust of metallic 
nickel on the negative electrode, often of a silvery lustre on the surface immediately 
* It may here be proper to remark, that by the word battery in the course of the following observations I 
always allude to the modification of Prof. Daniell’s battery described in § 4. 
MDCCCXXXVII. G 
