Congo red

Congo red
a water-soluble powder, C32H22O6N6S2Na2, one of the Congo colors that is not acid-fast or lightfast: used chiefly as a dye, biological stain, and chemical indicator.
[1880-85]

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      first of the synthetic dyestuffs of the direct (direct dye) type, that is, not requiring application of a mordant (a substance such as tannin or alum used to fix the colour to cotton fibres). Introduced in 1884, Congo red belongs to a group of azo dyes derived from benzidine. Congo red was formerly used to dye cotton but has been superseded by dyes more resistant to light and to washing. It is still used in histology to stain tissues for microscopic examination, and to serve as an acid-base indicator, since it turns red in the presence of alkalies and blue when exposed to acids.

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Universalium. 2010.

Look at other dictionaries:

  • Congo red — IUPAC name sodium sodium 3,3 ([1,1 biphenyl] 4,4 diyl)bis(4 aminonaphthalene 1 sulfonate) …   Wikipedia

  • Congo red — (Chem.) An artificial red dye from which the Congo group received its name. It is also widely used either in aqueous solution or as test paper ( {Congo paper}) for the detection of free acid, which turns it blue. [Webster 1913 Suppl.] …   The Collaborative International Dictionary of English

  • Congo red — n. a sodium salt, C32H22O6N6S2Na2, used for dyeing wool and cotton and as an acid base indicator: it becomes blue in an acid solution and remains red in an alkaline or neutral solution …   English World dictionary

  • Congo red — An acid direct cotton dye, it is absorbed by amyloid and induces green fluorescence to amyloid in polarized light; used as a laboratory aid in the diagnosis of amyloidosis, as a histologic stain, and as an …   Medical dictionary

  • congo red — noun a red brown azo dye especially as a chemical pH indicator (congo red is red in basic and blue in acidic solutions) • Topics: ↑solution • Hypernyms: ↑azo dye, ↑acid base indicator …   Useful english dictionary

  • congo red — kongo raudonasis statusas T sritis chemija apibrėžtis Indikatorius. formulė [NaSO₃(H₂N)C₁₀H₅N=NC₆H₄]₂ atitikmenys: angl. congo red rus. конго красный …   Chemijos terminų aiškinamasis žodynas

  • Congo red — /kɒŋgoʊ ˈrɛd/ (say konggoh red) noun one of the Congo colours, used especially to dye cotton, etc., red. Since it is not acid fast or light fast, it is often used as a chemical indicator …   Australian-English dictionary

  • Congo red — noun Etymology: Congo, territory in Africa Date: 1885 an azo dye C32H22N6Na2O6S2 that is red in alkaline and blue in acid solution and that is used especially as an indicator and as a biological stain …   New Collegiate Dictionary

  • Congo Red — Strukturformel Allgemeines Name Kongorot Andere Namen 3 …   Deutsch Wikipedia

  • Congo red — Naphthalene dye that is pH sensitive (blue violet at pH 3, red at pH 5). Used as vital stain, also in staining for amyloid …   Dictionary of molecular biology

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