Calcium 5-ethoxy-2-[(2-hydroxy-1-naphthyl)azo]benzenesulfonate;calcium 5-ethoxy-2-[(2-hydroxy-1-naphthyl)azo]benzenesulphonate;5-ethoxy-2-[(2Z)-2-(2-oxonaphthalen-1-ylidene)hydrazinyl]benzenesulfonate;5-Ethoxy-2-[(2-hydroxy-1-naphtyl)azo]benzenesulfonic acid/calcium,(1:x) salt