The present invention provides a method of manufacturing a reactive composition: (a) dissolving 2-[(4-aminophenyl)sulfonyl]ethanesulfonic acid in water to form a solution; (b) introducing excess nitrite or excess nitrous acid and the solution into an acid solution to form a diazonium salt; (c) adding 4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid to react with the diazonium salt; (d) adding 7-acetamido-4-hydroxy-2-naphthalenesulfonic acid to react with the diazonium salt; (e) adding a first alkaline substance to adjust a pH value; (f) adding a second alkaline substance to adjust the pH value; (g) adding a third alkaline substance to control the pH value; (h) adding an acidic substance to adjust the pH value; and (i) adding an additive agent to obtain the reactive composition, wherein the additive agent is acetic acid, sodium hydroxide, acetate, sulfonic acid buffering agent, or a combination thereof.

A reactive black dye composition is disclosed, which comprises: (A) a reactive blue dye represented by the following formula (I) or a salt thereof; and (B) a reactive red dye or a salt thereof, a reactive yellow dye or a salt thereof, or a combination thereof.

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Herein, R.sub.11, X.sub.1, X.sub.2, X.sub.31, X.sub.41 and n are defined in the specification. In addition, a method for dying fibers using the aforesaid reactive black dye composition is also disclosed.

The present invention provides a method of manufacturing a reactive composition: (a) dissolving 2-[(4-aminophenyl)sulfonyl]ethanesulfonic acid in water to form a solution; (b) introducing excess nitrite or excess nitrous acid and the solution into an acid solution to form a diazonium salt; (c) adding 4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid to react with the diazonium salt; (d) adding 7-acetamido-4-hydroxy-2-naphthalenesulfonic acid to react with the diazonium salt; (e) adding a first alkaline substance to adjust a pH value; (f) adding a second alkaline substance to adjust the pH value; (g) adding a third alkaline substance to control the pH value; (h) adding an acidic substance to adjust the pH value; and (i) adding an additive agent to obtain the reactive composition, wherein the additive agent is acetic acid, sodium hydroxide, acetate, sulfonic acid buffering agent, or a combination thereof.