2,7-Naphthalenedisulfonic acid, 4-amino-6-[2-[5-[(4-amino-6-chloro-1,3,5-triazin-2-yl)amino]-2-sulfo-4-[2-[4-[[2-(sulfooxy)ethyl]sulfonyl]phenyl]diazenyl]phenyl]diazenyl]-5-hydroxy-3-[2-[4-[[2-(sulfooxy)ethyl]sulfonyl]phenyl]diazenyl]-, sodium salt (1:?)