Morpholino ethanesulfonic acid

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Odorless, white crystalline material. Morpholino ethanesulfonic acid, or MES, is used as a buffering agent commonly used in biology and biochemistry. The mid-range buffer is water soluble, is stable in most chemicals and enzymes, and does not complex with metal ions. MES has minimal absorption in the UV/Vis spectral range.

Chemical structure

Morpholino ethanesulfonic acid.jpg

Synonyms and Related Terms

MES monohydrate; morpholino(ethanesulfonic acid); MES; 2-(N-morpholino) ethanesulfonic acid; 4-morpholineethansulfonic acid monohydrate;


  • Contact may cause irritation.
  • ThermoFisher: SDS

Physical and Chemical Properties

Soluble in water. pKa = 6.15

Composition C6H13NO4S . H20
CAS 4432-31-9
Melting Point ~300 C
Molecular Weight mol. wt. = 213.25

Resources and Citations

  • Richard C. Wolbers, Nanette T. Sterman, Chris Stavroudis, Notes for Workshop on New Methods in the Cleaning of Paintings, J.Paul Getty Trust, Los Angeles, 1990

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