The reaction at 300°C between molten lithium perchlorate and chromium(III) oxide gave lithium dichromate. When lithium perchlorate and chromium(III) oxide were in the formula weight ratio of 2:1 respectively, the chromium was oxidized completely into the hexavalent oxidation state, and only a negligible chloride percentage of 0·1 remained in the resulting lithium dichromate. Different formula weight ratios were taken for the reaction at 300°C. In the runs where the formula weight ratios of the perchlorate and oxide were lower than 2:1, the amount of chromium oxidized was higher than expected by the proposed route, and an explanation is given. Reactions with 51Cr2O3 showed that a very small amount of chromium volatilized. Results obtained from experiments both in vacuum and air were in very good agreement. A reaction mechanism is proposed.