of Gold and other Metals to Light. 417 
was no metal in some of the rings between other rings that re- 
flected brilliantly, but the metal was there of transmitting thick- 
ness: the transmitting 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 thm 
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. Gold produced a very thin film, too thin to be 
washed; it had a faint metallic reflexion, and transmitted a 
slate-blue colour like the former films. 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 explo- 
sion, and by transmission gave a dark gray colour. Iridium 
required much time, and formed 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 very little adhesion. Rhodiwm is reduced, 
but the film consists of floating particles, having so little adhe- 
sion that it cannot be gathered up. Stlver 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 varieties of thickness. Let a little oxide of copper 
be dissolved in olive-oil to form a bath, and having immersed 
some plates of glass, for which purpose microscope plates 3 x 1 
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, having 
the proper metallic lustre and colour by reflexion ; and by trans- 
mission, 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. 
{To be continued. ] 
Phil. Mag. 8. 4, Vol. 14, No, 95, Dec, 1857. 25 
