4-Hydroxy-2,7-naphthalenedisulfonic acid disodium salt; 1-Naphthol-3,6-disulfonic Acid Disodium Salt Hydrate; Disodium 4-Hydroxy-2,7-naphthalenedisulfonate Hydrate; Rudolf Guercke Acid Disodium Salt Hydrate; 4-Hydroxy-2,7-naphthalenedisulfonic Acid Disodium Salt Hydrate; Violet Acid Disodium Salt Hydrate cas no : 20349-39-7