Mordant anthraquinone dyes : Explained in brief
by : Rahul Sharma
Mordant anthraquinone dyes :
Mordant anthraquinone dyes have this property by the virtue of the presence of two hydroxyl groups in ortho positions in the anthraquinone structure. Alizarin and and its derivatives such as Alizarin Blue form metal complexes with metal salts such as salts of aluminium, chromium, copper, iron, tin, etc. For example, alizarin with aluminium, chromium, copper, iron and tin gives red, brown, yellowish brown brown and pink lakes respectively. These mordant dyes have high light fastness and were used earlier for calico printing, however, due to their lack in washing, perspiration and other fastness, they are now obsolate. The main use of dihydroxyanthraquinones such as alizar4in today is in the synthesis of anthraquinone intermediates. Alizarin is prepared by the alkali fusion of silver salt which is the sodium salt of anthraquinone-2-sulphonic acid.
