TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The base is an inorganic base which is chosen from sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate, preferably potassium carbonate. The hydrogen peroxide comprises 30-35% solution, content of hydrogen peroxide is 2-4.35 equivalents for treating 1-nitro-4-((4-nitrophenyl)sulfanyl)benzene of formula (I).The tungstate salt is sodium tungstate dehydrate, and the content of sodium tungstate dehydrate is 0.5-0.05 mol%.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The solvent is water or a mixture of solvents miscible with water, chosen from tetrahydrofuran, dioxane and 1-6C alkanol, preferably water/isopropanol mixture. Preferred Process: The preparation of 1-nitro-4-((4-nitrophenyl)sulfanyl)benzene of formula (I) further involves carrying out oxidation of 1-nitro-4-((4-nitrophenyl)sulfanyl)benzene of formula (I) to obtain 1-nitro-4-((4-nitrobenzene)sulfonyl)benzene of formula (V), by treating 1-nitro-4-((4-nitrophenyl)sulfanyl)benzene of formula (I) with hydrogen peroxide, in presence of a tungstate salt and of an acid, and reducing 1-nitro-4-((4-nitrobenzene)sulfonyl)benzene of formula (V), to obtain 4-4'-Diamino-diphenylsulphone (Dapsone) and, carrying out subsequent crystallization to obtain Dapsone as crystalline anhydrous form A, having XRPD spectrum in which most intense peaks fall at 10.39, 11.47, 11.77, 15.48, 18.04, 19.00, 19.56, 20.29, 20.83, and 21.79\|0.2?o in 2(~q). The reaction is carried out at pH of 1-6. The oxidation is carried out in a monophasic system, using 30% hydrogen peroxide in glacial acetic acid as oxidizing agent, at pH lower than 2, and 0.1 mol% or less sodium tungstate dehydrate, at 90-95?oC. Preferred Composition: The acid is a mineral acid, chosen from hydrochloric acid, sulfuric acid and phosphoric acid, or an organic acid chosen from acetic acid, methanesulphonic acid and a phosphonic acid, preferably phenylphosphinic acid. ACTIVITY - Dermatological; Antileprotic. No biological data given.    MECHANISM OF ACTION - None given.