Process for the preparation of Isosulphan Blue

1. 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.

2. The process as claimed in claim 1 , wherein the sulfonating agent is oleum in a concentration range of 20 to 70%.

3. The process as claimed in claim 1 , wherein the condensation is carried out at a temperature range of 80-110° C.

4. The process as claimed in claim 1 , wherein the condensation is carried on for 6 to 20 hours.

5. The process as claimed in claim 1 , wherein 4-[Bis[4-(diethylamino)phenyl]methyl]benzene-2,5-disulphonic acid disodium salt is isolated at a pH range of 9to 13.

6. The process as claimed in claim 1 , wherein the solvent is selected from a group of solvents consisting of methanol, ethanol, pronanol, isopropanol, butanol and isobutanol.

7. The process as claimed in claim 1 , wherein the acid is an aqueous sulphuric acid in a concentration range of 20 to 60%.