2,7-Naphthalenedisulfonic acid, 5-[[4-chloro-6-[[3-[2-[8-[[4-fluoro-6-(methylphenylamino)-1,3,5-triazin-2-yl]amino]-1-hydroxy-3,6-disulfo-2-naphthalenyl]diazenyl]-4-sulfophenyl]amino]-1,3,5-triazin-2-yl]amino]-4-hydroxy-3-[2-(1-sulfo-2-naphthalenyl)diazenyl]-, sodium salt (1:?)