title: Acid dissociation constants and pH values for standard "bes" and "tricine" buffer solutions in 30, 40, and 50 mass% dimethyl sulfoxide/water between 25 and -25 degrees C.
abstract: Information is given concerning two standard buffer solutions suitable as pH references in 30, 40, and 50 mass% dimethyl sulfoxide (DMSO)/H2O mixed solvents at subzero temperatures from -20 to 0 degrees C, with the intention of establishing a pH (designated pH*) scale. The two buffers selected were the ampholytes N,N-bis(2-hydroxyethyl)-2-aminoethane sulfonic acid ("bes") and N-tris(hydroxymethyl)methylglycine ("tricine"), and the reference standard consisted of equal molal quantities of the buffer and its respective sodium salt. The assignment of pH* values was based on measurements of the emf of cells without liquid junction of the type: Pt;H2(g,l atm) /Bes, Na Besate, NaCl / AgCl;Ag and Pt;H2(g,l atm) /Tricine, Na Tricinate, NaCl /AgCl;Ag and the pH* was derived from a determination of K2, the equilibrium constant for the dissociation process (Buffer)+/- in equilibrium with(Buffer)- + H+.
mesh_terms: D000476:Alkanesulfonates; D017738:Alkanesulfonic Acids; D002021:Buffers; D004121:Dimethyl Sulfoxide; D005615:Freezing; D005998:Glycine / Q000031:analogs & derivatives*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D013816:Thermodynamics; D014867:Water
chemical_list: D000476:Alkanesulfonates; D017738:Alkanesulfonic Acids; D002021:Buffers; D014867:Water; C012210:BES; D005998:Glycine; C100184:tricine; D004121:Dimethyl Sulfoxide