Manufacture of Bz-1-bromobenzanthrone

In a process for the manufacture of Bz-1bromobenzanthrone by brominating finely divided benzanthrone with bromine or a brominating agent in aqueous suspension, the improvement which comprises:

• suspending benzanthrone which has a mean particle size of 30 .mu.m or less in a single reaction medium consisting essentially of water;
• heating the suspension to 80.degree. or above;
• and
• then adding said bromine or brominating agent gradually to the suspension maintained at a temperature above 80.degree. C., the molar ratio of the added bromine or brominating agent to benzanthrone being approximately 1:1, thereby resulting in yields of Bz-1-Bromobenzanthrone of at least about 91%.