How is Disodium 9,10-dioxo-9,10-dihydro-2,7-anthracenedisulfonate (CAS: 853-67-8) typically synthesized?

Disodium 9,10-dioxo-9,10-dihydro-2,7-anthracenedisulfonate is synthesized through a multi-step process involving the sulfonation of anthracene, followed by the oxidation of the resulting sulfonic acid to form the dioxo derivative. The synthesis typically uses sulfur trioxide or oleum as the sulfonating agent, and ferric chloride as a catalyst. The overall yield is around 70-80%, and the product is purified by recrystallization from appropriate solvents.