5-Chloro-2-methoxy-4-nitrobenzenamine diazo, and 1-Naphthol-4,8-disulfonic acid?coupling, and then with aqueous acid chromium common heating (125 ~ 135 ℃), make its formed chromium complex. In the complex process medium armor oxygen radicals displacement into hydroxyl, and 4-from sulfonic acid sodium base there will be 20% off.
