5th change. Copper--sensibly darkened. " Silver--unchanged. " Copper--deep red. " Silver--unchanged. " Copper--red, blue. " Silver--pale gold. " Copper--white, orange of the 2d order. " Silver--yellow. " Copper--green of the 1st order, red 3rd order. " Silver--blue.
The affinity of chlorine with silver is much inferior to that which it possesses for copper.
Iodine at the common temperature has no action upon this metal.
Bromine, when the surface of this substance is perfectly dry, has no more action upon it than iodine; but if it have a slight coating of moisture, as is formed by merely condensing on it the vapor of the breath, the colored films are formed without difficulty by the vapors of bromine. Their appearance is the same as those of the iodide of silver, viz. gold, deep gold, blue, white, yellow, orange, red, &c.
Titanium has a stronger affinity than it has for either of the preceding vapors. The combination takes place when the metallic surface is either dry or moist.
Copper--much reddened. Titanium--not affected. Copper--passed through several of the spectral orders of red and green until it arrived at almost its last changes of colors.
Titanium under the same action received a dull film, which viewed obliquely showed red, green, yellow.
Silver, exposed to the same influence as the two former, had yellow in the centre and blue more externally.
Silver--pale gold. Bismuth--some parts yellow, others not attacked. Silver--blue, white, yellow-orange. Bismuth--blue, yellow, orange.
In the action of iodine on bismuth, the influence of the physical condition of metallic surface is very manifest. The crystaline texture of this metal may be perceived, and the difference of its hardness admits, to a certain point, of being measured by the difference of the color of the films that are formed on various points; while most parts are yellow, there exist others of an angular outline which remain still unattacked; the same difference is remarked in the other stages of the combination.
It is impossible to estimate the affinity between mercury and iodine by means of the colored films, because, on combining, these two substances merely cause a dirty white appearance on the surface of the latter. Their combining affinity appears to be considerable, for when exposed together with silver the action produced with both was red at the edges, little altered in color; on the rest of its surface a dull white film, in the midst of which were seen several dark spots, where the metal was apparently unaltered.