PURPOSE: To prepare the titled compound useful as a raw material for the preparation of an intermediate of dye, in high yield, by nitrating naphthalenetrisulfonic acid with nitric acid, and reducing the nitrated mixture with iron under acidic conditions in the presence of inorganic sulfur-containing compound or sulfur.
CONSTITUTION: Naphthalenetrisulfonic acid is nitrated with nitric acid, and the nitrated mixture is reduced with iron under acidic conditions to obtain partial alkali metal salt of 1-aminonaphthalene-3,6,8-trisulfonic acid (Koch's acid). The reduction is carried out in the presence of an organic sulfur-containing compound such as sodium sulfite, potassium sulfite, sulfur dioxide gas, sodium bisulfate, etc. or sulfur, at ≤3pH, preferably ≤2pH. The yield of Koch's acid in the acidic reduction can be improved by the addition of the sulfur compound, and the present process promotes the H-acid (dye intermediate) preparation process including an acidic reduction process, and gives industrial advantage.
OOI SAKUO
OKABE HIROMICHI
INOUE KIKUMITSU
KAJIWARA HIROYUKI
KORENAGA YOUJI
NUNO TATSUMI
