Acid red 195 is a chemical compound, a synthetic monoazoic red dye consisting of a chromium complex.

Chemical name

Sodium 4-[(4,5-dihydro-3-methyl-5-oxo-1-phenyl-1H-pyrazol-4-yl)azo]-3-hydroxynaphthalene-1-sulphonate

Acid Red 195 is a synthetic monoazo dye known for its vibrant red color. It is commonly used in various industrial applications, including textiles, leather, and paper, due to its excellent color properties and stability.

Chemical Composition and Structure

Acid Red 195 is a monoazo dye, meaning it contains a single azo group (-N=N-) in its molecular structure. It is also a chromium complex, which enhances its stability and colorfastness. The chemical formula for Acid Red 195 is C18H14CrN3O8S. The structure includes an azo group linked to aromatic rings and complexed with chromium, contributing to its distinctive red hue.

Physical Properties

Acid Red 195 typically appears as a red powder. It is soluble in water and exhibits excellent stability under various conditions, including resistance to light and heat. The chromium complexation enhances its overall durability and color retention.

Chemical Industrial Synthesis Process

• Preparation of reagents. The main raw materials include a benzene derivative (such as aniline), sulfuric acid (H₂SO₄), sodium nitrite (NaNO₂), a base (such as sodium hydroxide (NaOH)), and a chromium salt (such as chromium chloride (CrCl₃)).
• Diazotization. The benzene derivative is treated with sulfuric acid and sodium nitrite to form a diazonium intermediate. This reaction produces a diazonium salt.
• Coupling. The diazonium salt is then coupled with another aromatic compound in the presence of a base, such as sodium hydroxide, to form the azo compound intermediate.
• Formation of the chromium complex. The azo compound intermediate is then treated with a chromium salt, such as chromium chloride, to form the chromium complex. This reaction produces the Acid Red 195 dye.
• Filtration. The resulting suspension is filtered to separate the solid precipitate from the aqueous solution.
• Washing. The precipitate is washed with deionized water to remove any soluble impurities.
• Drying. The washed precipitate is dried at controlled temperatures to remove residual moisture and obtain a dry powder.
• Grinding. The dried product is ground to obtain a fine and uniform powder.
• Classification. The dried powder is classified to ensure a uniform particle size. This step may involve sieving or the use of air classifiers.
• Stabilization. The Acid Red 195 powder is stabilized to ensure its stability during transportation and storage, preventing aggregation and degradation.
• Quality control. The Acid Red 195 undergoes rigorous quality testing to ensure it meets standards for purity, color intensity, and safety. These tests include chemical analysis, spectroscopy, and physical tests to determine particle size and rheological properties.

What it is used for and where

Cosmetics

Restricted cosmetic ingredient as  IV/153 a Relevant Item in the Annexes of the European Cosmetics Regulation 1223/2009. Substance or ingredient reported:

• Sodium 4-[(4,5-dihydro-3-methyl-5-oxo-1-phenyl-1H-pyrazol-4-yl)azo]-3-hydroxynaphthalene-1-sulphonate. Maximum concentration in ready for use preparation: Not to be used in products applied on mucous membranes

Cosmetics - INCI Functions

Colorant. This ingredient has the function of colouring the solution in which it is inserted in a temporary, semi-permanent or permanent manner, either alone or in the presence of the complementary components added for colouring.

CAS   12220-24-5

EC number    222-811-0

UNII    W038OX77W2

Synonyms:

CI 18760

Safety

 The problem associated with azo dyes (monoazo or diazo) is photocatalytic degradation leading to eventual oxidation and subsequent formation of impurities such as aromatic amines some of which have carcinogenic activity (1).

It is an ingredient that has some important health-related contraindications: it should not come into contact with mucous membranes.

References__________________________________________________________________________

(1) Chung KT, Stevens SE Jr, Cerniglia CE. The reduction of azo dyes by the intestinal microflora. Crit Rev Microbiol. 1992;18(3):175-90. doi: 10.3109/10408419209114557.

Abstract. Azo dyes are widely used in the textile, printing, paper manufacturing, pharmaceutical, and food industries and also in research laboratories. When these compounds either inadvertently or by design enter the body through ingestion, they are metabolized to aromatic amines by intestinal microorganisms. Reductive enzymes in the liver can also catalyze the reductive cleavage of the azo linkage to produce aromatic amines. However, evidence indicates that the intestinal microbial azoreductase may be more important than the liver enzymes in azo reduction. In this article, we examine the significance of the capacity of intestinal bacteria to reduce azo dyes and the conditions of azo reduction. Many azo dyes, such as Acid Yellow, Amaranth, Azodisalicylate, Chicago Sky Blue, Congo Red, Direct Black 38, Direct Blue 6, Direct Blue 15, Direct Brown 95, Fast Yellow, Lithol Red, Methyl Orange, Methyl Red, Methyl Yellow, Naphthalene Fast Orange 2G, Neoprontosil, New Coccine, Orange II, Phenylazo-2-naphthol, Ponceau 3R, Ponceau SX, Red 2G, Red 10B, Salicylazosulphapyridine, Sunset Yellow, Tartrazine, and Trypan Blue, are included in this article. A wide variety of anaerobic bacteria isolated from caecal or fecal contents from experimental animals and humans have the ability to cleave the azo linkage(s) to produce aromatic amines. Azoreductase(s) catalyze these reactions and have been found to be oxygen sensitive and to require flavins for optimal activity. The azoreductase activity in a variety of intestinal preparations was affected by various dietary factors such as cellulose, proteins, fibers, antibiotics, or supplementation with live cultures of lactobacilli.