Product Description
Acid Red 18, CAS 2611-82-7, is a synthetic red azo dye also known as C.I. 16255 and Ponceau 4R. It is commonly supplied in the form of a trisodium salt and has the molecular formula C₂₀H₁₁N₂Na₃O₁₀S₃, with a reference molecular weight of approximately 604.46 g/mol.
The molecule contains an azo chromophore and multiple sulfonate groups. The azo structure contributes to its visible red coloration, while the sulfonate groups support its affinity for water. The material is typically supplied as a red to dark-red powder, and it can form a red-colored aqueous solution when dissolved under suitable conditions. The final shade and color strength depend on dye concentration, solution pH, the surrounding ingredients, and the quality of the supplied grade.
Acid Red 18 is associated with food-coloring applications in certain regulatory systems, but approval is not universal. Its permitted uses, maximum levels, labeling requirements, and purity criteria vary by jurisdiction and food category. A product listing or CAS number alone does not establish that a particular grade is suitable for use in food. Buyers should verify the applicable food-grade specification and current regulatory authorization for the intended market.
The dye may also be relevant to selected laboratory and industrial coloring processes where its shade and water solubility meet the process requirements. Such applications require separate assessment of color fastness, substrate compatibility, processing conditions, and the required technical grade.
For quality assessment, the most relevant parameters include dye content, identity, moisture, insoluble matter, subsidiary colorants, and applicable impurity limits. The specific analytical methods and acceptance criteria should be agreed according to the intended use. Where food applications are considered, the supplied batch documentation should demonstrate compliance with the applicable food-colorant requirements rather than relying solely on general chemical reference data.
Chemical Properties
| Property | Details |
|---|---|
| Product Name | Acid Red 18 |
| CAS Number | 2611-82-7 |
| Colour Index | C.I. 16255 |
| Common Synonyms | C.I. Acid Red 18; Ponceau 4R; New Coccine |
| Chemical Name | Trisodium 7-hydroxy-8-[(4-sulfonato-1-naphthyl)azo]-1,3-naphthalenedisulfonate |
| Molecular Formula | C₂₀H₁₁N₂Na₃O₁₀S₃ |
| Molecular Weight | Approximately 604.46 g/mol |
| Chemical Class | Synthetic azo dye |
| Ionic Form | Trisodium salt |
| Appearance | Typically red to dark-red powder; confirm against the supplied grade |
| Water Solubility | Soluble in water, producing a red solution |
| Principal Chromophore | Azo group |
| Functional Groups | Azo and sulfonate groups, with hydroxyl functionality in the dye structure |
| Color in Aqueous Solution | Red; the exact shade depends on concentration and solution conditions |
| Food Additive Identifier | E124 / INS 124 in relevant regulatory systems; verify local authorization |
| Storage | Keep in tightly closed packaging in a dry area, protected from moisture and contamination; follow the supplied SDS |
Product Applications
1. Permitted Food-Coloring Applications
Where authorized, food-grade Acid Red 18 may be used to provide red coloration in specified food categories. The permitted products, maximum use levels, and labeling conditions must be confirmed under the current regulations of the destination market.
2. Aqueous Color Preparation
Its water-soluble structure makes Acid Red 18 suitable for evaluation in water-based color preparations. Dissolution behavior and final color strength should be tested at the intended concentration and under the actual processing conditions.
3. Laboratory and Analytical Work
Acid Red 18 may be used as a reference or test material in suitable analytical procedures involving dye identification, absorption characteristics, or color measurement. The required purity and documentation depend on the method and whether quantitative analysis is intended.
4. Textile and Material Coloring
Selected non-food grades may be evaluated for coloring compatible materials in industrial processes. Suitability depends on substrate chemistry, application conditions, required shade, wash resistance, and other fastness requirements.
5. Industrial Colorant Formulation
In appropriate industrial systems, Acid Red 18 may be assessed where a water-compatible red dye is required. Compatibility with other ingredients, stability during processing, and performance on the intended substrate should be established through testing.
FAQ
Q1: What is Acid Red 18?
Acid Red 18 is a synthetic red azo dye identified by CAS number 2611-82-7 and Colour Index number C.I. 16255. It is commonly associated with the name Ponceau 4R.
Q2: What are its molecular formula and molecular weight?
The molecular formula of the trisodium salt is C₂₀H₁₁N₂Na₃O₁₀S₃, and its reference molecular weight is approximately 604.46 g/mol.
Q3: Is Acid Red 18 soluble in water?
Yes. It is water-soluble and produces a red-colored solution. Actual color strength and shade depend on concentration, solution conditions, and the supplied grade.
Q4: Is Acid Red 18 permitted in all food products?
No. Authorization varies by country or region and by food category. Confirm the current regulations, permitted use levels, labeling requirements, and food-grade specifications before selecting the material for a food application.
Q5: What should buyers check before purchasing Acid Red 18?
Verify the CAS number, Colour Index identity, dye content, moisture, insoluble matter, relevant impurity limits, and batch-specific certificate of analysis. For food use, also confirm that the grade and intended application meet the destination market's requirements.
