摘要：

Discloses an azo compound or a salt thereof represented by the following formula (1) or (2). (In the formula, A represents a substituted phenyl or naphthyl group having 1-3 sulfonic acid groups; X is represents -N = N- or -NHCO-; R1-R4 independently represent a hydrogen atom, a lower alkyl group or lower alkoxy; m represents a value ranging from 1-3; n-represents 0 or 1).

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