Anthraquinone-1,5-disulfonic acid
, Thiol Acid, and anthraquinone-
1,8-disulfonic acid , Azine
Acid, are produced by disulfonation
under conditions similar to those for monosulfonation
except for an increased concentration
of SO3 . After sulfonation of the anthraquinone
is complete, the 1,5-acid is precipitated
by slow addition of dilute sulfuric acid, collected,
and washed with dilute sulfuric acid. The
filter cake is dissolved in hot water, the solution
treated with charcoal, and the anthraquinone-
1,5-disulfonic acid precipitated from the filtrate
as its disodium salt by addition of saturated
sodium chloride solution. The 1,8-acid is isolated
as the potassium salt from the sulfuric acid
mother liquors and the wash acids (see also
and ). Mercury can be removed in a
similar manner as given for anthraquinone-1-
sulfonic acid (see, e.g., ).
