PROCESS FOR THE PREPARATION OF THE DISODIUM SALT OF 1,5-NAPHTHALENEDISULPHONIC ACID

摘要

1. Process for the preparation of the disodium salt of naphtalene-1,5-disulphonic acid from sulphonation mixtures which are obtained in the preparation of naphtalene-1,5-disulphonic acid and are possibly diluted with water, characterized in that the sulphonation mixtures used are those such as are obtained in the suphonation of napththalene with 2.3-5.0 moles of sulphur trioxide per mole of naphthalene in an inert organic solvent, and in that these suphonation mixtures are neutralised with sodium hydroxide or sodium carbonate to a pH value of 5 to 9 and the disodium salt which precipitates is isolated, in a manner know per se, from suspension formed during the neutralisation.