Description

Direct Red 81 is a synthetic, water-soluble azo dye belonging to the direct dye class, known for its strong affinity to cellulosic fibers. This product is valued for its ability to produce vibrant, wash-fast red shades on cotton, viscose, and other natural materials without the need for a mordant. It is primarily needed by manufacturers in the textile dyeing and paper coloring industries, where consistent color strength and batch-to-batch uniformity are critical for production quality.

Application

• Textile Dyeing: Primary application for dyeing cotton, rayon, linen, and other cellulosic fibers to achieve a bright red hue.
• Paper Coloring: Used in the production of colored papers, tissues, and packaging materials.
• Leather Finishing: Imparts color to leather goods in the tanning industry.
• Ink Formulation: A colorant component in certain types of inks for stamp pads and specialty printing.
• Biological Staining: Potential use as a histological stain in laboratory settings.
• Educational & Research: Serves as a standard or reference dye in chemical research and academic laboratories.

Basic Information

Product Name	Direct Red 81
CAS No.	12237-71-7
Molecular Formula	C29H19N5Na2O8S2
Molecular Weight	675.60 g/mol
Synonyms	Direct Red 81; C.I. 28160; Benzo Scarlet 4BS; Pontamine Scarlet 4BS; Sirius Scarlet 4BS; Direct Scarlet 4BS; Direct Fast Scarlet 4BS; Aizen Direct Scarlet 4BH
EINECS	235-468-3

Quality Control

Our Direct Red 81 is manufactured under a stringent quality management system to ensure high purity and consistent performance. Each batch is tested against key parameters including color strength, solubility, and shade conformity. A comprehensive Certificate of Analysis (COA) detailing purity, heavy metal content, and other relevant specifications is provided with every shipment to guarantee it meets the requirements for industrial applications.

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 strong oxidizing agents.

Specification

Item	Specification
Appearance	Reddish-brown powder
Identification (IR)	Conforms to standard
Color Strength	≥ 98% (vs. Standard)
Moisture Content	≤ 5.0%
Water Insoluble Matter	≤ 1.0%
pH (1% Solution)	6.0 - 8.0
Heavy Metals (as Pb)	≤ 50 ppm

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