758. 4-[(8-Acetamido-l-hydroxy-3,6-disulfonato-2-naftyl)azo]-4'-[(6-benzamido-1-hydroxy-3-sulfonato-2-naftyl)azo]bifenyl-3,3'-diol, měďnatý komplex, trisodná sůl (ES 413-590-3)