Mordant in pyrolignite of
alumina at 10 deg. B., and wash thoroughly. Dye for an hour at 70 deg., and half
an hour longer at the same heat, using for 100 kilos of cloth or yarn 20
kilos alizarin at 10 per cent., 10 kilos acetate of lime at 18 deg. B., and
5 kilos sulpholeic acid. Steam for an hour. Soap for a longer or shorter
time, with or without the addition of soda crystals. There may be added
to the aluminous mordant a little salt of tin to raise the tone. Lastly,
aluminate of soda may be used as a mordant in place of red liquor or
sulphate of alumina.
Certain firms employ a so-called continuous process. The pieces are
passed into a cistern 6 meters long and fitted with rollers. This
dye-bath contains, from 3 to 5 grms. of alizarin per liter of water, and
is heated to 98 deg.. The pieces take 5 minutes to traverse this cistern,
and, owing to the high temperature and the concentration of the dye
liquor, they come out perfectly dyed. Two pieces may even be passed
through at once, one above the other. As the dye-bath becomes exhausted,
it must be recruited from time to time with fresh quantities of
alizarin. The great advantage of this method is that it economizes not
merely time but coloring matter.
The quantity of acetate of lime to be employed in dyeing varies with the
composition of the mordant and with that of the water. Schlumberger has
shown that Turkey-red contains 4 molecules of alumina to 3 of lime.
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