Description

C.I. Acid Red 81 is a synthetic, water-soluble azo dye belonging to the acid dye class, valued for its bright red color and good affinity for protein-based fibers. Its primary commercial value lies in providing vibrant, wash-fast coloration to nylon, wool, and silk textiles, as well as in specialized staining applications. This dye is essential for manufacturers in the textile, leather, and specialty paper industries, and for laboratories requiring a biological stain. The compound is identified by CAS No. 6846-33-9.

Application

• Textile Dyeing: Primary application for dyeing nylon, wool, silk, and other polyamide fibers to achieve bright red shades.
• Leather Coloring: Used for dyeing leather goods, providing rich and uniform color penetration.
• Paper Staining: Employed in the production of colored papers, including specialty and decorative papers.
• Biological Staining: Functions as a histological stain in laboratory settings for microscopic analysis.
• Ink Formulation: A colorant component in the manufacture of certain inks, including stamp pad and flexographic inks.
• Wood Staining: Used to impart color to wood veneers and other porous materials.

Basic Information

Product Name	C.I. Acid Red 81
CAS No.	6846-33-9
Molecular Formula	C18H13N3Na2O8S2
Molecular Weight	509.42 g/mol
Synonyms	Acid Red 81; Acid Leather Red BG; Amido Naphthol Red G; Azo Rubine S; C.I. 45160; Acid Fast Red A; Naphthalene Red J; Acid Brilliant Rubine; Lissamine Red 4B; Acid Magenta
EINECS	229-934-2

Quality Control

Our C.I. Acid Red 81 is manufactured under a stringent quality management system to ensure batch-to-batch consistency and performance. Each lot is tested against rigorous in-house specifications for key parameters including color strength, shade, solubility, and impurity profile. A comprehensive Certificate of Analysis (COA) detailing purity, physical properties, and conformance is provided with every shipment.

Storage

Preserve in a tightly closed container, protected from light. Store in a cool, dry, and well-ventilated area at room temperature (15-25°C). Keep away from incompatible materials. Due to its light-sensitive nature, prolonged exposure to direct light should be avoided to prevent color degradation.

Specification

Item	Specification
Appearance	Red to dark red powder
Identification (IR)	Conforms to standard
Assay (HPLC)	≥ 95.0%
Color Strength	100 ± 3% (vs. Standard)
Moisture Content	≤ 5.0%
Water Solubility	Conforms
Ash Content	≤ 1.0%
Heavy Metals (as Pb)	≤ 20 ppm

Note: Specifications can be tailored. Please contact us for the detailed technical data sheet of a specific grade.