Di:benzothiophene-5,5-di:oxide-3,7-sulphonic acid prodn. - from di:phenyl and oleum, useful as additive in galvanising

摘要

Prodn. of dibenzothiophene-5, 5-dioxide-3, 7-disulphonic acid (I) comprises reacting diphenyl (II) with oleum con 5-70 (20-659 wt.% SO3, at 100-250 (150-210) degrees C. Pref. 1-20 moles SO3 are used per mole (II). Esp. (II) is reacted first with oleum contg. 20 wt.% SO3 (1 mole SO3 per mole (II)), then further oleum contg. 65 wt.% SO3 added to provide another 2-5 moles SO3 per mole (II). (I) is useful as a galvanising additive esp. to provide shiny surface coatings in galvanic Ni deposition. High yields of high purity (I) contg. 1% mono- or tri-sulphonic acids.