Syonyms Name: C.I. 22120; C.I. Direct Red 28; C.I. Direct Red 28, disodium salt; C.I. Direct Red 28, disodium salt (8CI); Congo red; Direct Red 28; Congo red (0.1% in water)[for titration]; Congo red (0.1% in water); Direct Scarlet 4B; disodium 3,3'-[biphenyl-4,4'-diy