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To dye woollens black

Wool is dyed black by the following process. It is boiled for two hours in a decoction of nutgalls, and afterwards kept, for two hours more, in a bath, composed of logwood and sulphate of iron, kept, during the whole time, at a scalding heat, but not boiling. During the operation, it must be frequently exposed to the air; because the green oxide of iron, of which the sulphate is composed must be converted into red oxide by absorbing oxygen, before the cloth can acquire a proper colour. The common proportions, are five parts of galls, five of sulphate of iron, and thirty of logwood, for every hundred of cloth. A little acetate of copper is commonly added to the sulphate of iron, because it is thought to improve the colour.