Cadmium Brown

: ON THE SEMI-NEUTRAL, BROWN.

By igniting the white carbonate of cadmium, among other methods, a

cinnamon-brown oxide is obtainable, of a very clear and beautiful colour

if the process be well conducted. It is, however, not eligible as a

pigment, owing to the rapidity with which the oxide is acted upon by the

air. In water, especially, we have found this brown so eagerly absorb

carbonic acid from the atmosphere as to become in a few months once more

a carbonate, and as purely white as before. The same result is

observable when the powder is exposed: some shown at the International

Exhibition of 1862, on a glass stand, had to be removed, its label

marked 'Cadmium Brown' being at last found attached to a sample of

cadmium white. In oil, the conversion takes place less readily, that

vehicle having the property of protecting, to some extent, pigments from

oxidation. It is curious that even in a book a water-rub of the brown

slowly but surely changes to white.



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