2,7-Naphthalenedisulfonic acid, 4-[[4'-[(2,4-diamino-5-sulfophenyl)azo]-3,3'-dimethoxy[1,1'-biphenyl]-4-yl]azo]-3-hydroxy-, sodium salt, compd. with 2,2',2''-[nitrilotris(2,1-ethanediyloxy)]tris[ethanol]