Acid Red Dyes: Uses, Properties, and Applications

Nov 26, 2025 0

Acid Red dyes are a class of synthetic anionic dyes primarily used for coloring textiles, leather, and paper. These dyes are characterized by their ability to bind to materials in acidic conditions, offering vibrant and lasting colors. Due to their intense color, solid samples often appear almost black.

Acid red 266 is a multifunctional dye. Dyes are important tools in biological experiments. They can help researchers observe and analyze cell structures, track biomolecules, evaluate cell functions, distinguish cell types, detect biomolecules, study tissue pathology and monitor microorganisms. Their applications range from basic scientific research to clinical diagnostics.

Here's a look at various aspects of acid red dyes, including their properties, applications, and safety considerations.

Chemical and Physical Properties

Acid Red dyes generally have the following properties:

Description: Typically available as a deep-maroon or red powder.
Melting Point: Decomposes at 250-300 °C.
Solubility: Soluble in water (80 g/L at 80 °C) and slightly soluble in ethanol.

Synthesis

Acid Red 88 can be obtained by azo coupling of naphthionic acid and 2-naphthol. Instead of crystallising, it vitrifies when cooled or salted out of the solution.

Applications of Acid Red Dyes

Acid Red dyes are used across various industries for their coloring properties.

Dyeing and Textile Industry: This chemical is commonly used as a dye for textiles, providing vibrant colors that are resistant to fading.
Food Industry: It serves as a food coloring agent, enhancing the visual appeal of products like candies and beverages.
Biological Research: Acid red 1 is employed as a staining agent in microscopy, helping researchers visualize cellular structures and processes.
Cosmetics: The compound is also found in cosmetic formulations, providing color to products such as lipsticks and blushes.

Specific Acid Red Dyes and Their Uses

Acid Red 1

Acid Red 1 is employed as a staining agent in microscopy, helping researchers visualize cellular structures and processes.

Acid Red 88

Acid red 88 is an azo dye. Acid Red 88 is used in combination of Fenton's reagent and ultrasound irradiation.

Acid Red 114

CI Acid Red 114 is used to dye wool (from a weak acid bath), silk (from either a neutral or acetic acid bath), jute and leather. Wool and silk are also printed directly.

CI Acid Red 114, a bright red anionic bisazo dye, is manufactured by converting 3,3′-dimethylbenzidine (ortho-tolidine) to the tetraazonium salt, which is then coupled successively to G acid (2-naphthol-6,8-disulfonic acid) and phenol. The phenol hydroxy function is then esterified with para-tolylsulfonyl chloride.

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CI Acid Red 114 has been produced commercially since the early 1900s. In the USA there were six manufacturers and two importers of CI Acid Red 114 in 1977.

Acid Red 266

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Safety and Regulations

In Germany, CI Acid Red 114 must be handled like the corresponding hypothetical reduction amine, 3,3′-dimethylbenzidine, which is classified as an A2 compound. Such materials are considered to have been proven to be carcinogenic only in animal experimentation but under conditions comparable to those of possible human exposure at the workplace.

Environmental Impact and Degradation

Anaerobic biodegradation of CI Acid Red 114 gives rise to the amine metabolites, 3,3′-dimethylbenzidine and 4-methylbenzenesulfonic acid (4′-aminophenyl) ester. Following incubation of 100 mg/l of dyestuff at 35 °C in the presence of anaerobic sludge inoculum, primary degradation was complete within seven days.

Several methods have been developed to degrade Acid Red 1, including:

Using chemically modified sugarcane bagasse-based biocomposites.
Catalyzed by peroxidase activity of iron oxide nanoparticles and detected by SERS.
Solar photoelectro-Fenton-like process using electrogenerated HClO and photoregenerated Fe(II).
Green synthesis of nanocatalysts based on reduced graphene oxide/magnetic nanoparticles.
Laccase immobilized on Zein-Polyvinyl pyrrolidone nano fibrous membrane in decolorization of Acid Red 1.

Experimental Studies

Carcinogenicity

CI Acid Red 114 was tested for carcinogenicity in one study in rats by administration in the drinking-water. It increased the incidences of benign and malignant tumours of the skin, Zymbal gland and liver in male and female rats, and of the clitoral gland, lung, oral cavity and small and large intestine in female rats.

Genetic Effects

CI Acid Red 114 was mutagenic to Salmonella typhimurium strains TA1538 and TA98 under reducing conditions. It did not induce sex-linked recessive lethal mutation in Drosophila melanogaster and did not induce unscheduled DNA synthesis in primary cultures of rat hepatocytes or sister chromatid exchange or chromosomal aberrations in cultured Chinese hamster ovary cells.

Hair Dyeing Formulations

Hair dyeing formulations belong to three categories - temporary, semi-permanent and permanent coloring of hair. The permanent hair dyeing formulations are often referred to as oxidative hair dyes which are generally marketed as two-component products.

One component contains the compounds (precursors) that become the colorants and the other component is a stabilized solution of hydrogen peroxide. The two components are mixed immediately prior to use. The precursors and peroxide diffuse into the hair shaft, where color formation takes place after the ingredients combine to produce the coloring mixture.

The precursors are oxidized by the hydrogen peroxide to form the colorant molecules. These molecules are too large to escape from the hair structure. The hydrogen peroxide in the oxidative hair dye product also serves as bleaching agent for the natural pigment of the hair.