Paint Its Colouring Matter Or Anchusin Has The Character Of A Resin
:
ON THE SECONDARY, PURPLE.
and is dark-red, softened by heat, insoluble in water, soluble in
alcohol and alkalis, and freely so in ether, fats, and volatile oils, to
all of which it imparts a brilliant red hue. To obtain anchusin, all the
soluble matters are first abstracted from the bruised root by water: it
is then digested in a solution of carbonate of potash, from which it may
be readily precipitated by an acid. Its alcoholic solution yields with
different reagents crimson, flesh-coloured, blue, and violet
precipitates, none of which, however, can be classed as durable. The
variety under notice, violet carmine, resembles the other colours
afforded by alkanet in not being able to withstand the action of light.
On continued exposure, it loses its beauty and brightness, together with
much of its colour, and, like Indian purple, assumes an inky blackness.
Hence it is unsuited to permanently pure effects, and should only be
used in body.
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