Description:
<jats:p>By a spectrophotometric method the acid-base equilibrium between bromcresol green and triethanolamine was measured over the range of temperature from −6°C to +50°C in the three solvents—methanol, ethanol, and n-butanol. In each solvent the equilibrium constant was found to vary rapidly with temperature; and in methanol the value of logK was found to change sign near 0°C. This behavior is very different from the well-known results for weak acids in aqueous solution, and in the theoretical part of the paper a unified theory is presented to cover all types of proton transfer. The work required to transfer a proton consists of two parts, a part sensitive to the environment and a part insensitive to the environment; the behavior of the equilibrium constant depends on whether the two parts are of the same sign or of opposite sign. Families of curves are drawn to show the various possible types of behavior.</jats:p>