Wood-tar Blue





The colours obtained from coal-tar have become household words, and it

is not impossible that those from wood-tar may be some day equally

familiar. At present wood-tar is comparatively unexplored, but the fact

that picamar furnishes a blue is at least as suggestive and hopeful as

that transient purple colouration by which aniline was once chiefly

distinguished. As aniline is a product of coal-tar, so picamar is a

product of wood-tar; and as the former gives a purple with

hypochlorites, so the latter yields a blue with baryta-water. Both are

distinguished by coloured tests, but there is this advantage in the

picamar blue--it is comparatively permanent.



Picamar blue is produced when a few drops of baryta-water are added to

an alcoholic solution of impure picamar, or even to wood-tar oil

deprived of its acid. The liquor instantly assumes a bright blue tint,

which in a few minutes passes into an indigo colour. From [Greek: pitta]





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