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