Patent ID: 7534911

Claim:
A process for the preparation of Isosulphan Blue, said process comprising the following steps: (a) sulphonating orthochlorobenzaldehyde with a sulphonating agent to obtain 4-chloro-3-formyl sulphonic acid; (b) treating 4-chloro-3-formyl sulphonic acid with sodium sulphite and subsequent basification thereof to obtain 1-formyl benzene-2,5-sulphonic acid disodium salt; (c) condensation reacting of 1-formyl benzene-2,5-sulphonic acid disodium salt with N,N-diethylaniline using hydrochloric acid to obtain a 4-[Bis[4-(diethylamino)phenyl]methyl]benzene-2,5-disulphonic acid disodium salt (d) oxidation reacting of 4-[bis[4-(diethylamino)phenyl]methyl]benzene-2,5-disulphonic acid with ammonium dichromate as an oxidizing agent, using an acid and a solvent, to obtain Isosulphan Blue.