2,7-Naphthalenedisulfonic acid, 4-hydroxy-3-[[4'- [(4-hydroxyphenyl)azo][1,1'-biphenyl]-4-yl]azo]-5-[[3- [(8-hydroxy-6-sulfo-2-naphthalenyl)azo]-2-aminophenyl]azo]- ?-amino-, trisodium salt NSC47771