Naphthalene → Naphthalene trisulfonic acid

Participants

Reaction Steps

It is known from FIAT Final Report No. 1016, pages 32 to 39, that H-acid can be prepared as follows: naphthalene is reacted with sulphuric acid monohydrate (=100% strength H2SO4) and 65% strength oleum, a certain temperature programme being maintained and the sulphuric acid monohydrate and oleum being added stepwise, to give a naphthalene-trisulphonic acid isomer mixture which is nitrated with mixed acid. After diluting the mixture with water, driving off the nitrous fumes and removing the sulphuric acid as calcium sulphate, the isomer mixture of the nitronaphthalene-trisulphonic acids is reduced with iron and dissolved iron salts are then precipitated with magnesium oxide and separated off. The acid calcium-sodium salt of T-acid (1-naphthylamine-3,6,8-trisulphonic acid) is precipitated by adding sodium chloride and hydrochloric acid, and is filtered off and repeatedly washed. This salt is introduced into wash water and sodium carbonate is added. The calcium carbonate which has precipitated is then removed on a filter press and the salt solution is concentrated. The concentrated trisodium salt solution of T-acid is reacted with 50% strength sodium hydroxide solution under pressure. Thereafter first sulphuric acid and then water are added and finally the H-acid is isolated as the monosodium salt by filtration, washing and drying.

Provenance & Evidence