β-Naphthol is the most important dye intermediaters in the preparation of azo dyes, and is made by the alkali fusion of β-naphthalene sulfonic acid with sodium hydroxide.
This study on sulfonation aimed at the production of β-naphthalene sulfonic acid and carried out in varying temperatures between 130。- 160 ℃ for about 8 hrs, where the initial mole ratio of sulfonic acid vs to naphthalene was used 1:1.
Sampling was taken by the time intervals of 0.5 or 1 hr. The unreacted sulfonic acid in the sample was analyzed by titration with M/100 EDTA and both of α-and β-sulfonic acid which was produced during the reaction was analyzed by using "Euwes's solubility chart of Pb salt".
From the result of this experiment, it was found that this reaction was nothing but a first order consecutive reversible one though this reaction was expressed as follows,
"naphthalene+sulfonic acid [<-->] α-naphthalene sulfonic acid+water [<-->] β-naphthalene sulfonic acid+water"