Xylenol Orange

[3H-2,1-Benzoxathiol-3-ylidenebis(6-hydroxy-5-methyl-m-phenylene)methylenenitrilo]tetra-acetic acid S,S-dioxide tetrasodium salt, Tetrasodium 3,3′-(3H-2,1-benzoxathiol-3- ylidene)bis[(6-hydroxy-5-methyl-3,1-phenylene)methyleneiminobisacetate] S,S-dioxide; C₃₁H₂₈N₂Na₄O₁₃S = 761 (3618-43-7)

Reddish-brown crystalline powder, soluble in water.