Direct Blue 183 Direct blue 183 (C.I. 31951) 6-[(4-Amino-3-methoxyphenyl)azo]-4-hydroxy-3-[[4'-[(1-hydroxy-4-sodiosulfo-2-naphthalenyl)azo]-3,3'-dimethoxy[1,1'-biphenyl]-4-yl]azo]naphthalene-2-sulfonic acid sodium salt C.I.31951 C.I.Direct Blue 183 Diazo Blue 2B C.I.Direct Blue 183:C.I.31951