Ortho Nitro Chloro Benzene Para Sulphonic Acid ( ONCBPSA) Synonyms: 3 Nitro 4 Chlorobenzenesulphonic acid ( sodium salt) Empirical Formula: C6 H4 O5 N S Cl CAS No. ( sodium salt) : 17691 - 19 – 9 CAS No. ( free acid) : 121-18-6 Purity ( Amine value) : 60 % Minimum Uses: Intermediate for Dyes and in synthesis of other intermediates