1-[3-[[(4-Amino-9,10-dihydro-9,10-dioxo-3-sulfoanthracen)-1-yl]amino]-5-sulfophenyl]-4,5-dihydro-5-oxo-4-[[4-[[2-(sulfooxy)ethyl]sulfonyl]phenyl]azo]-1H-pyrazole-3-carboxylic acid 3-methyl ester