Trisodium hydrogen [2-[[α-[[3-[[4-chloro-6-[ethyl[3-[[2-(sulphooxy)ethyl]sulphonyl]phenyl]amino]-1,3,5-triazin-2-yl]amino]-2-hydroxy-5-sulphophenyl]azo]benzyl]azo]-4-sulphobenzoato(6-)]cuprate(4-)