Cotton Seed Blue

Cotton seed oil is bleached by treatment with either carbonate of soda

or caustic lime. In both cases, a considerable residue is left after

drawing off the bleached oil. This residue is treated with sulphuric

acid, and distilled at a high temperature, when there is left a compact

mass of a deep greenish-blue colour. On further treatment of this mass

with strong sulphuric acid, the green tint disappears, and a very

intense pure blue colour is produced. The blue mass is a mixture of the

coloured substance with some sulphuric acid, sulphate of soda, and fats.

The two former may be removed by washing with water; the latter by

treatment with naptha. Alcohol now dissolves the blue colour, and water

precipitates it from the solution chemically pure.

This blue has not been introduced as a pigment; and of its permanence,

and other attributes, we know nothing.

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