1-Hydroxynaphthalene-3-sulfonic acid [3771-14-0]. (4-hydroxynaphthalene-2- sulfonic acid), C10H8O4S, Mr 224.2, and its salts are very soluble in water. Coupling with diazo compounds occurs in the 2-position with weak diazo compounds, but in the 4-position with strong diazo compounds such as diazotized nitroanilines. Heating with ammonia at 170℃ gives 1,3-naphthalenediamine.
1-Hydroxynaphthalene-3-sulfonic acid is used as a coupling component for the production of direct dyes.
1-Aminonaphthalene-3-sulfonic acid is heated with dilute sulfuric acid by using high-pressure steam to maintain a pressure of 1 MPa for 20 h. After cooling, screening, and adding salt to the hot liquor, the sodium salt crystallizes on cooling and is isolated in 80 % yield.
