Congo red

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 indicator (pH 3.0, blue-violet, to pH 5.0, red) in testing for free hydrochloric acid in gastric contents. See Bennhold C. stain.

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Congo red .käŋ-(.)gō-'red n an azo dye C32H22N6Na2O6S2 that is red in alkaline and blue in acid solution and that is used in a number of diagnostic tests and esp. for the detection of amyloidosis since the injected dye tends to be retained by abnormal amyloid deposits

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a dark-red or reddish-brown pigment that becomes blue in acidic conditions. It is used as a histological stain. amyloidosis is indicated if over 60% of the dye disappears from the blood within one hour of injection.

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an odorless, dark red or reddish brown powder that decomposes on exposure to acid fumes; used as a biological stain, as an indicator with a pH range of 3.0 (blue-violet) to 5.2 (red), and as a diagnostic aid in amyloidosis See also under tests.

Medical dictionary. 2011.

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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 — Chem. 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] * * * ▪ dyestuff       first of the synthetic dyestuffs of the… …   Universalium

  • 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 paper — filter paper wet with a 0.2 per cent solution of Congo red in water, dried, and cut in strips …   Medical dictionary

  • Congo red test — (for amyloidosis) Congo red is injected intravenously; if more than 60 per cent of the dye disappears after 1 hour, amyloidosis is indicated …   Medical dictionary

  • 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 …  

  • 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

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