congo red: meaning, definition, pronunciation and examples
C2Technical/Scientific
Quick answer
What does “congo red” mean?
A direct azo dye first synthesized in 1884, named after the Congo region. It is a benzidine-based red dye that changes color to blue in acidic conditions (pH below 3.
Audio
Pronunciation
Definition
Meaning and Definition
A direct azo dye first synthesized in 1884, named after the Congo region. It is a benzidine-based red dye that changes color to blue in acidic conditions (pH below 3.0), making it a common pH indicator.
In scientific contexts, 'Congo red' is also used in histology to stain amyloid proteins in tissue samples, where it produces an apple-green birefringence under polarized light, aiding in the diagnosis of diseases like Alzheimer's and amyloidosis.
Dialectal Variation
British vs American Usage
Differences
No significant differences in usage or spelling. The chemical nomenclature is identical.
Connotations
Purely technical; no cultural or regional connotations.
Frequency
Equally rare outside of chemistry, biology, histology, and textile dyeing contexts in both regions.
Grammar
How to Use “congo red” in a Sentence
The tissue was stained *with* Congo red.Congo red *is used* to detect amyloid.The solution *contained* 0.1% Congo red.Vocabulary
Collocations
Examples
Examples of “congo red” in a Sentence
verb
British English
- The sections were then *congored* to visualise the amyloid deposits. (Rare, technical jargon)
American English
- The protocol instructs you to *Congo-red-stain* the tissue. (Rare, technical jargon)
adverb
British English
- [No standard adverbial use]
American English
- [No standard adverbial use]
adjective
British English
- The *Congo-red-stained* slide was examined under the microscope.
American English
- A *Congo-red-positive* result is indicative of amyloidosis.
Usage
Meaning in Context
Business
Rare, except in business related to laboratory supplies, dyes, or histopathology reagents.
Academic
Common in research papers and textbooks for chemistry, histology, biochemistry, and medical diagnostics.
Everyday
Virtually never used.
Technical
The primary domain of use. Refers precisely to the chemical compound used for staining or pH indication.
Vocabulary
Synonyms of “congo red”
Strong
Neutral
Weak
Vocabulary
Antonyms of “congo red”
Watch out
Common Mistakes When Using “congo red”
- Writing it as 'congored' (should be two words or hyphenated: Congo red or Congo-red).
- Using lowercase 'c' for 'Congo'.
- Using it as a general term for the colour red.
FAQ
Frequently Asked Questions
Yes, it was named in 1884 by its German inventors, likely in connection with the contemporary colonial Conference of Berlin which involved the Congo region.
Originally, it was developed as a direct cotton dye ('Direct Red 28'), but its lightfastness is poor, limiting its modern commercial use in textiles.
Its specific binding to the beta-pleated sheet structure of amyloid proteins allows doctors to diagnose serious conditions like Alzheimer's disease, AA amyloidosis, and others through tissue biopsy staining.
As a benzidine derivative, it is considered a potential carcinogen and must be handled with appropriate laboratory safety precautions, including gloves and fume hoods.
A direct azo dye first synthesized in 1884, named after the Congo region. It is a benzidine-based red dye that changes color to blue in acidic conditions (pH below 3.
Congo red is usually technical/scientific in register.
Congo red: in British English it is pronounced /ˌkɒŋɡəʊ ˈrɛd/, and in American English it is pronounced /ˌkɑːŋɡoʊ ˈrɛd/. Tap the audio buttons above to hear it.
Phrases
Idioms & Phrases
- “[No idioms exist for this technical term]”
Learning
Memory Aids
Mnemonic
Think: 'Congo Red turns Blue when Acid is fed.' Links the name, colour, and its function as an acid indicator.
Conceptual Metaphor
N/A. It is a literal, referential term for a chemical entity.
Practice
Quiz
In which field is Congo red most commonly used?