The following is a process for the preparation of a black dye, for which
a patent was taken out at Vienna by M. Honig:--Logwood is to be boiled
several times in water, and a little sub-carbonate of potash to be added
to the decoctions, the quantity being so moderated that it shall not
change the colour to blue; the stuff to be dyed is then to be plunged
into this bath. This stuff may be either animal or vegetable. When it is
well impregnated with colouring matter, it is to be withdrawn, and,
without being exposed to air, is to be introduced into a solution of
green-vitriol, and left there until it has obtained the desired black
hue. In preparing the _ink_, the decoction of logwood is used in
place of the infusion of galls.
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