Direct Red 31

Chemical Properties

Reddish brown powder. Water solubility is still good, aqueous solution is bluish red, add concentrated hydrochloric acid to produce date red precipitate, add concentrated alkali to orange-brown. Soluble in ethylene glycol ether, slightly soluble in ethanol, reddish orange, insoluble in other organic solvents. Orange to brown in concentrated sulfuric acid, produces dark blue-red precipitate after dilution; brown solution with precipitate in concentrated nitric acid. Insoluble in concentrated alkali; date red in concentrated ammonia.

Uses

Direct red 31 is a good dyeing agent for cotton fabrics.

Properties and Applications

Standard	Acid Resistance	Alkali Resistance	Light Fastness	Soaping		Water
				Fading	Stain	Fading	Stain
ISO	3-4	4	2	1-2		1-2
AATCC	3-4	4	1	1		1-2

References

[1] Sawada K, Ueda M. Adsorption behavior of direct dye on cotton in non-aqueous media[J]. Dyes and pigments, 2003, 58(1): 37-40.