4-[[4-[[2-(diethylamino)ethyl]sulphonyl]-2,5-dimethoxyphenyl]azo]-4,5-dihydro-5-oxo-1-(4-sulphophenyl)-1H-pyrazole-3-carboxylic acid, sodium salt

4-[[4-[[2-(Diethylamino)ethyl]sulfonyl]-2,5-dimethoxyphenyl]azo]-4,5-dihydro-5-oxo-1-(4-sulfophenyl)-1H-pyrazole-3-carboxylic acid/sodium,(1:x) salt