| abstract |
A process is provided for the preparation of naphthalene-1,3-5,-trisulphonic acid from 1,5-disulphonated naphthalene, which comprises sulphonating 1,5-disulphonated naphthalene, in the form of a mixture which has been obtained by mixing naphthalene and SO 3 in the presence of an inert solvent at temperatures in the range of -40° to +20° C., the ratio of SO 3 added to naphthalene added having been in the range of 2.5 to 10 mols of SO 3 per mol of naphthalene during the entire addition, at 60° to 110° C. in anhydrous sulphuric acid with oleum, with prior or concurrent separation of the inert solvent. n The resulting product is a known intermediate for the formation of azo dyestuffs. |