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Methyl Red Indicator ACS, Ph Eur C.I. 13020

Price: £13.95
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Stock Availability
On Shelf - Approx. UK delivery date: Wednesday the 01st October 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
  • pH Indicator
  • Identification of bacteria in Microbiology

C.I. 13020 (Acid Red 2)

Methyl red (2-(N,N-Dimethyl-4-aminophenyl)azobenzenecarboxylic acid), also called C.I. Acid Red 2, is an indicator dye that turns red in acidic solutions. It is an azo dye, and is a dark red crystalline powder. Methyl red is a pH indicator; it is red in pH under 4.4, yellow in pH over 6.2, and orange in between, with a pKa of 5.1.

C.I. 13020

  • Molecular Formula: C15H15N3O2
  • Molecular Weight: 269.30
  • Melting Point: 179-182 deg C
  • Absorption Min (pH 4.5 Buffer): 523-526nm
  • Absorption Max (pH 4.5 Buffer): 427-437nm
  • Specific Absorptivity (A1%/1cm): 1350-1450 (0.005g/L Buffer pH 4.5)
  • Specific Absorptivity (A1%/1cm): 700-800 (0.005g/L Buffer pH 6.2)
  • Transition Range: pH 4.4-6.0 (Red-Yellow)
  • Loss on Drying (110degC): <5%

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