Acid Red 249

Acid Red 249 is an anionic acid dye — a water-soluble, dark-red to magenta powder used for acidic dyeing of protein and polyamide fibres and for other soluble-dye applications.

Dark red powder, soluble in water, slightly soluble in ethanol for product red, the strong sulfuric acid for product red, diluted for pink; Join the hydrochloric acid solution for red; Add sodium hydroxide to brown. Metal ion to the colored light no effect.

Appearance is dark red powder. Soluble in water, slightly soluble in ethanol, magenta. In concentrated sulfuric acid, it is magenta, diluted to pink. The aqueous solution is red, hydrochloric acid is added red; sodium hydroxide is added to brown.

TRADE NAME:

Weak Acid Brilliant Red B

Product features

Appearance: Dark red to magenta powder, fully water-soluble under standard acidic dyebath conditions.
Fastness: Good washing and moderate to good light fastness in many substrates (performance varies with fiber and finishing).
pH sensitivity: Shade and solubility change with pH—acidic baths favor red shades; alkali can darken or precipitate.
Compatibility: Works well on protein fibers (wool, silk) and polyamide (nylon); compatibility with other dye classes depends on recipe and auxiliaries.
Typical uses: Textile dyeing/printing, paper coloring, some soluble dye applications in plastics/thermosets.
Storage: Store dry, protected from light and moisture; keep sealed at cool temperature to preserve strength.

Application:

Used for wool, silk and polyamide fiber fabric dyeing and printing, but also for direct dyes and with bath dyeing wool/rayon blended fabric.

Acid Red 249 Use condition:

‍1. Mainly used for dyeing and printing of wool, silk and nylon fabrics, and also for leather dyeing.
2. Wool dyeing: generally carried out in a neutral bath, the pH value of the dyeing solution is adjusted to 6~7. If the pH of the dyeing solution is lower than 6, even if the temperature is lower than 80 °C, the dyeing is still faster, and the dyeing problem is easy to occur. , Yuanming powder as a retarding agent, the leveling effect is not obvious. For compact fabrics, it should be dyed with ammonium sulfate and organic leveling agent after neutral dyeing bath. When dyeing dark color, in the post-boiling stage Acetic acid is added to increase the exhaustion rate.
3. Silk dyeing: It can be carried out in a weakly acidic or neutral bath, and it can be dyed by adding acetic acid or Yuanming powder.
4. Nylon dyeing: It can be carried out in neutral or weak acid bath, and the wet processing fastness on nylon is better.
5. Spinning dyeing: When the wool is dyed in the same bath with various fibers, the apparent color of nylon is close to that of wool, the silk is lighter, the polyester is stained, and the cellulose fiber is not stained. It can be dyed with the direct dye in the same bath. .
6. Weakly Acidic Red B is often dyed with a variety of red with weakly acidic red F-3GL.
7. Metal ions have no effect on shade.

Common applications

Used for dyeing and printing wool, silk, nylon/polyamide, some paper and specialty polymer/thermoset/thermoplastic formulations where soluble acid dyes are appropriate. Suitable for textile wet-processing and selected industrial coloration tasks.

Technical Specifications

‍CAS NO: 6416-66-6
CI.NO: 18134
Molecular Formula:C29H20C1N3Na2O10S3
Molecular Weight:748.11
Shade:red blue light‍

Standard	Fiber	Soaping		Persperation Fastness	Oxygen bleaching	Light Fastness
Standard	Fiber	Fading	Stain	Persperation Fastness	Oxygen bleaching	Light Fastness
AATCC	Wool				4	3
ISO	Wool	2	3	4	4	5

Leveling(grade)	Displacement	Whitening	Solubility(g/L)	Metal ion effect(grade)
				copper	iron	chromium
3~4	C	well	80(90℃)	4	5	4

Colour Fastness Test

Test Methods	fiber	Alkali resistance	Carbonization	Chlorination discoloration	Oxygen bleaching	Alkali fluff		Acid fluff		potting		soaping		Perspiration	Sun exposure
						discolor	Staining	discolor	Staining	discolor	Staining	discolor	Staining
AATCC	wool	2	5	—	4	4	3	—	—	—	—	—	—	—	3
ISO	wool	2~3	4	3~4	4	3~4	3	3~4	3~4	2	2	2	3	4	5

What fibers take Acid Red 249 best, and which do not?

Acid Red 249 performs best on protein fibers (wool, silk) and polyamides (nylon) under acidic dyebath conditions—these substrates produce strong, even shades. It is not recommended for most cellulose-based fibers (cotton) unless used with a suitable mordant or as a combined printing system; direct cellulose dyeing will give poor exhaustion and fastness compared to reactive or direct dyes.

How does Acid Red 249 behave with pH changes or metal ions?

The dye is pH-sensitive: concentrated strong acid can shift the shade toward magenta, while strong alkali may darken or cause browning/precipitation. Several sources report that common metal ions have limited effect on shade, but precipitation can occur if incompatible chemicals (e.g., certain cationic polymers or basic dyes) are present — perform compatibility trials before scale-up.

Can Acid Red 249 be used in thermoplastics or thermoset colorings?

Yes — there are commercial formulations that use soluble acid dyes for coloring certain thermosets/thermoplastics and paper, but heat stability and migration must be checked. Acid Red 249 will not behave like a pigment (it’s soluble), so evaluate bleed, migration and thermal stability under your processing conditions before adoption.