Also Called: 1,3-Naphthalenedisulfonic acid, 7-[(1,8-dihydroxy-3,6-disulfo- 2-naphthalenyl)azo]-, tetrasodium salt;1,3-Naphthalenedisulfonic acid, 7-[2-(1,8-dihydroxy-3,6-disulfo-2-naphthalenyl)diazenyl]-, sodium salt (1:4);1,3-Naphthalenedisulfonic acid, 7-[(1,8-dihydroxy-3,6-disulfo-2-naphthalenyl)azo]-, tetrasodium salt