3 ml of aqueous extract was shaken with 3 ml
of benzene, filtered and 5 ml of 10% ammonia solution was added
to the filtrate. The mixture was shaken and the presence of a pink,
red or violet colour in the ammonical (lower) phase indicates the
presence of free anthraquinones.
(b) 3 ml of the aqueous extract was boiled with 3 ml of aqueous
sulphuric acid and filtered while hot. 3 ml of benzene was added to
the filtrate and shaken. The benzene layer was separated and 3 ml
of 10% NH3 added. A pink, red or violet colouration in the
ammonical (lower) phase indicates the presence of anthraquinone
derivatives.