158 
DE. FAEADAY ON THE EXPEEBIENTAL EELATIONS 
gave fine films, apparently very continuous and stiff; the reflexion was strong and 
metallic, of a dark grey colour ; the transmission presented every shade of Indian ink. 
Platinum chloride gave traces of a film excessively thin, and very slow in formation. 
Ehodium chloride in three or four hours gave a beautiful film of metal in concentric 
lings, varying in reflecting and transmitting power over light and also in colour ; those 
which reflected well, transmitted little hght ; and those which transmitted, reflected little 
light ; one might have thought there was no metal in some of the rings between other 
rings that reflected brilliantly, but the metal was there of transmitting thickness ; the 
transmitted colour of rhodium varied from brown to blue. Silver : a solution of the 
nitrate gave films showing the concentric rings; the light transmitted by the thinner 
parts was of a warm brown, or sepia tint ; the film becomes very loose and mossy in the 
thicker parts and is wanting in adherence ; pressure brings out the full metallic lustre in 
every part, and in the thin places converts the colour from brown to blue, being in that 
respect like the result with pale gold-leaf, in which the silver present dominates over 
the colour of the gold. I do not think there is phosphorus combined with this silver ; I 
did not find any, and considering the surface action on metals which float as films 
between air and water, it seems improbable that it should be there. 
Hydrogen was employed to reduce some of the metals, their solutions being placed in 
an atmosphere of the gas. The action differed considerably from that of phosphorus, as 
might be expected. Oold produced a very thin film, too thm to be washed ; it had a 
faint metallic reflexion, and transmitted a slate-blue colour hke the former film s. 
Platinum chloride was acted on at once ; minute spots appeared here and there on the 
surface ; these enlarged, became rough and corrugated at the middle, though brilliant 
at the edges, and at last formed an irregular coat over the fluid ; at the part where the 
film was flat and brilliant, it resembled that produced by the electric explosion, and by 
transmission gave a dark grey colour. Iridium required much time, and fonned a crust 
from centres like the platinum. Palladium gave an instant action, but most of the 
reduced metal sunk in a finely divided state ; a film may be obtained, but it has veiy 
little adhesion. Rhodium is reduced, but the film consists of floating particles, ha'sing 
so little adhesion that it cannot be gathered up. Silver is reduced, but the film is 
very thin and has no tenacity. 
A copper film of very beautiful character may be obtained as follows in all vaiieties 
of thickness. Let a little oxide of copper be dissolved in ohve-oil to form a bath, and 
having immersed some plates of glass, for which purpose microscope plates 3x1 inches 
are very convenient, let the whole be heated up to the decomposing temperature of the 
oil ; being left to cool, and the plates then drained and washed successively in camphine 
and alcohol, they will be found covered -with a film of copper, haring the proper metallic 
lustre and colour by reflexion ; and by transmission, presenting a green colour, which, 
though generally inclining to olive, is in the thinner films often more beautiful than the 
green presented by pressed gold. 
