CUPRATE(4-),[.MU.-[[3,3'-[(3,3'-DI(HYDROXY-.KAPPA.O)[1,1'-BIPHENYL]-4,4'-DIYL)BIS(AZO-.KAPPA.N1)]BIS[4-(HYDROXY-.KAPPA.O)-2,7-NAPHTHALENEDISULFONATO]](6-)]]DI-,TETRASODIUM