Product name:Direct Red 28
CAS:573-58-0
Molecular Formula:C32H22N6Na2O6S2
Formula Weight:696.66
Description:
Specification:25g
Direct Red 28 is the sodium salt of benzidinediazo-bis-1-naphthylamine-4-sulfonic acid (formula: C32H22N6Na2O6S2; molecular weight: 696.66 g/mol). It is a secondary diazo dye. Congo red is water soluble, yielding a red colloidal solution; its solubility is better in organic solvents such as ethanol.
It has a strong, though apparently non-covalent affinity to cellulose fibres. However, the use of congo red in the cellulose industries (cotton textile, wood pulp & paper) has long been abandoned, primarily because of its tendency to change color when touched by sweaty fingers, to run, and because of its toxicity.