THERMODYNAMICS OF THE 2ND DISSOCIATION OF A SUBSTITUTED AMINOPROPANESULFONIC ACID (TAPSO) FROM 5-DEGREES-C TO 55-DEGREES-C

Electromotive force (emf) measurements of the cell without a liquid ju nction of the type Pt\H-2\TAPSO (m(1)) + NaTAPSOate (m(2)) + NaCl (m(3 ))\AgCl\Ag were made at intervals of 5K from 5 degrees C to 55 degrees C, including 37 degrees C, with stoichiometric molalities m(1)=m(2)=m (3) ranging from 0.01 to 0.1 mol . kg(-1). At 25 degrees C, pK(2) is 7 .635, and consequently buffer solutions of TAPSO and its salt (NaTAPSO ate) are useful for pH control in the region pH 6 to 8. The second dis sociation constant (pK(2)) of TAPSO can be expressed by the equation 2 254.0057/(T/K)-4.9783+0.88672 In(T/K), with a standard deviation of +/ -0.0008. The zwitterionic buffer TAPSO is represented as droxymethyl)m ethyl)amino]-2-hydroxypropanesulfonic acid, a derivative of the parent compound taurine.