| 摘要 |
Tortoiseshell and like natural materials are more or less decolourized by bleaching agents which yield nascent oxygen, e.g. hydrogen peroxide. The material may be treated over a period in a series of baths of increasing strength or in a single bath. The action may be accelerated by light, ultra violet radiations and electric currents and superatmospheric pressure may be employed. Substances which promote liberation of oxygen may be added to the baths, e.g. ferrous chloride or sulphate, sodium carbonate or silicate, alkaline earth hydroxides, sodium phosphate. Stabilizing substances may be added to prevent too rapid evolution of oxygen when it is necessary to work at a higher temperature than usual, e.g. formic or phosphoric acid, sodium chloride, metaphosphate and pyrophosphate, ethyl alcohol, glycerol, glycol ethers, ethyl ether, acetanilide, &c. The treated material may be further treated with formaldehyde, or solutions of free or combined chlorine. Substances of a softening nature such as mixtures of oils and fats, soaps, glycerol, sulphonation products such as sulphoricinoleic acid may be added to render the product more pliable.
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