C.I. 24400; C.I. Direct Blue 15; C.I. Direct Blue 15, tetrasodium salt; C.I. Direct Blue 15 (8CI); Direct Blue 15; Direct sky blue; Direct Turquoise Blue 5B; tetrasodium (3E,3'E)-3,3'-[(3,3'-dimethoxybiphenyl-4,4'-diyl)di(1E)hydrazin-2-yl-1-ylidene]bis(5-amino-4-oxo-3,4-dihydronaphthalene-2,7-disulfonate); (3Z)-5-amino-3-({4'-[(2E)-2-(8-amino-1-oxo-3,6-disulfonaphthalen-2(1H)-ylidene)hydrazino]-3,3'-dimethoxybiphenyl-4-yl}hydrazono)-4-oxo-3,4-dihydronaphthalene-2,7-disulfonic acid; tetrasodium 3,3'-[(3,3'-dimethoxybiphenyl-4,4'-diyl)dihydrazin-2-yl-1-ylidene]bis(5-amino-4-oxo-3,4-dihydronaphthalene-2,7-disulfonate); tetrasodium (3Z,3'Z)-3,3'-[(3,3'-dimethoxybiphenyl-4,4'-diyl)di(1Z)hydrazin-2-yl-1-ylidene]bis(5-amino-4-oxo-3,4-dihydronaphthalene-2,7-disulfonate); sodium (6E)-4-amino-6-(2-{4'-[(2E)-2-(8-amino-1-oxo-3,6-disulfonaphthalen-2(1H)-ylidene)hydrazinyl]-3,3'-dimethoxybiphenyl-4-yl}hydrazinylidene)-5-oxo-7-sulfo-5,6-dihydronaphthalene-2-sulfonate