1,7-Naphthalenedisulfonic acid, 6-[(3,6-disulfo-2-naphthalenyl)azo]-5-hydroxy-2-[[4-[[4-[[2-(sulfooxy)ethyl] sulfonyl]phenyl]amino]-6-[(4-sulfophenyl)amino]-1,3,5-triazin-2-yl]amino]-