Benzenesulfonic acid, 3-​chloro-​4-​[4,​5-​dihydro-​3-​methyl-​5-​oxo-​4-​[2-​(4-​sulfophenyl)​diazenyl]​-​1H-​pyrazol-​1-​yl]​-​5-​methyl-​, sodium salt (1:2)