CUPRATE(6-),[.MU.-[[2,2'-[(1,4-DIOXO-2-BUTENE-1,4-DIYL)BIS[IMINO(2-SULFO-4,1-PHENYLENE)-2,1-ETHENEDIYL(3-SULFO-4,1-PHENYLENE)[4,5-DIHYDRO-3-METHYL-5-(OXO-.KAPPA.O)-1H-PYRAZOLE-4,1-DIYL]AZO-.KAPPA.N1]]BIS[5-SULFOBENZOATO-.KAPPA.O]](10-)]]DI-,HEXASODIUM