diammonium hydrogen 2-amino-4-[(4-amino-3-sulphonatophenyl)(4-imino-3-sulphonatocyclohexa-2,5-dien-1-ylidene)methyl]toluene-3-sulphonate

ChEBI: An organic sodium salt that is the disodium salt of 2-amino-5-[(4-amino-3-sulfophenyl)(4-imino-3-sulfocyclohexa-2,5-dien-1-ylidene)methyl]-3-methylbenzene-1-sulfonic acid. It is used in the Van Gieson method in conjunction with picric acid to demonstrate c llagen fibres red, and in Masson's trichrome to colour smooth muscle in contrast to collagen.