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.
