2,2'-Dihydroxy-4'-sulpho-1,1'-azonaphthalene-3-carboxylic acid 2-Hydroxy-1-(2-hydroxy-4-sulfo-1-napthylazo)-3-naphthoic acid 2-Naphthalenecarboxylic acid, 3-hydroxy-4-((2-hydroxy-4-sulfo-1-naphthalenyl)azo)- 3737-95-9 Calcon 3-carboxylic acid Calconcarbonic acid Calconcarboxylic acid EINECS 223-117-0 NN NSC 97307 Patton and Reeder's indicator Patton-Reeder indicator