Product Overview

Congo Red is a direct diazo dye widely used as both a pH indicator and a biological stain, particularly in histology and pathology. It exhibits a pH-dependent color change from blue to red over the pH range of 3.0 to 5.2 and is commonly used to detect acidic changes in aqueous solutions.

In biological applications, Congo Red is well known for staining amyloid deposits, where it produces a characteristic apple-green birefringence under polarized light. It is also used to differentiate cell wall components in microbiology and to highlight elastic and connective tissue in histological preparations.

Key Features:

• pH transition range: 3.0 (blue) to 5.2 (red)
• High affinity for amyloid proteins and cellulose
• Compatible with polarizing microscopy
• Available in powder or solution form
• Stable and reproducible staining performance

Applications:

• Histological staining of amyloid plaques and connective tissue
• Microbiological differentiation of bacterial species
• Acidic pH detection in chemical and environmental testing
• Research in neurodegenerative disease and protein aggregation
• General laboratory staining and instructional use

Congo Red remains a trusted dye in both analytical and biological sciences for its vivid color properties, binding specificity, and utility in both pH measurement and diagnostic staining.