4,4'-bis[[2,5-dimethyl-4-[(4-sulphophenyl)azo]phenyl]-N,N,O-azoxy]stilbene-2,2'-disulphonic acid, ammonium sodium salt

2,2'-(1,2-Ethenediyl)bis[5-[[2,5-dimethyl-4-[(4-sulfophenyl)azo]phenyl]-NNO-azoxy]benzenesulfonic acid]/ammonia/sodium,(1:x:x) salt