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Congo Red C.I. 22120

Price: £10.89
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Stock Availability
On Shelf - Approx. UK delivery date: Thursday the 11th September 2025*
In bulk stock - ships within 10 - 12 Working Days (Excluding weekends and public holidays)
4 to 6 weeks approx. (Not guaranteed)
UK Shipping

Unfortunately, we are not currently accepting orders for Northern Ireland.

We can only ship to the following postcodes where a Royal Mail postal option has been chosen at checkout.

AB, DD, DG3, DG4, DG6 - DG9, EH, FK, G, HS, IM, IV, KA, KW, KY, ML, PA, PH, PO30 - PO41, TD, TR21 - TR25, ZE

* We will always try to ship as early as possible. Delivery could be much quicker than stated but is not guaranteed
  • Biological Dye
  • Amyloid Stain
  • pH Indicator

In biochemistry and histology, Congo Red is used to stain microscopic preparates, especially as a cytoplasm and erythrocyte stain. Apple-green birefringence of Congo Red stained preparates under polarized light is indicative for the presence of amyloid fibrils. Additionally, Congo Red is used in microbiological epidemiology to rapidly identify the presence of virulent serotype 2a Shigella flexneri, where the dye binds the bacterium's unique lipopolysaccharide (LPS) structure.

  • C.I. 22120
  • Molecular Formula: C32H22N6S2Na2
  • Molecular Weight: 696.66 g/mol
  • Melting Point: 360 C
  • Absorptivity (@lambda max): 585nm
  • Loss on drying: <2.5%
  • Transition Range (3.5-5): Blue-red

Hazard Phrases: Causes serious eye irritation. May cause cancer .

Prec Phrases: Obtain special instructions before use. Use personal protective equipment as required. IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing. IF exposed or concerned: Get medical advice/attention.

respiratory CLP Image Harmful CLP Image

Cas No: 573-58-0
Einecs No: 209-358-4

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Source Chemicals Ltd