5Cr2O3 + 3H2SO4 + 2H2O + 6NaBrO3 → 5H2Cr2O7 + 3Br2 + 2Na2SO4
Chromium(III) oxide react with sulfuric acid, water and sodium bromate to produce dichromic acid, bromine and sodium sulfate. Sulfuric acid - diluted solution. The reaction takes place in a boiling solution.