Activity coefficients from e.m.f. measurements using cation-responsive glass electrodes. NaCl + glycine + water at 273.15, 283, 15, 298.15, and 323.15 K

Activity coefficients of electrolyte and amino acid in the systems (water + potassium chloride +dl -valine) at T=298.15 K and (water + sodium chloride +l -valine) at T= 308.15 K

“…Most measurements of the activity coefficients of amino acids in aqueous electrolyte solutions have been made by the isopiestic (3)(4)(5) and the electrochemical methods. (6)(7)(8)(9) The only direct experimental method for determining the activity coefficient of a solute in an electrolyte solution is by means of electromotive force measurements. Electrochemical cells with ion-selective electrodes are important tools that are used to measure the activity coefficients of the electrolytes.…”

Interaction ofDL-threonine with NaCl and NaNO3in aqueous solutions: e.m.f. measurements with ion-selective electrodes

“…Figure 3 shows, using the molality of DL-threonine as a parameter, the ratio of the activity coefficients of DL-threonine in the presence of NaCl and in the absence of NaCl as a function of NaCl molality. The solid lines are those obtained from equation (6) with parameters presented in table 3. Figure 3 also shows that the presence of NaCl affects the activity coefficient of the DL-threonine.…”

“…Figure 4 shows the ratio of the activity coefficients of DL-threonine in the presence of NaNO 3 and in the absence of NaNO 3 , at the same DL-threonine FIGURE 3. Effect of DL-threonine and NaCl molalities m on the ratio of the activity coefficients g (2) /g (1) of DL-threonine: a, m(DL-threonine) = 1.4 mol·kg molality, as a function of NaNO 3 molality, obtained from equation (6). As is shown in figure 4, the presence of NaNO 3 , for a fixed DL-threonine molality, decreases the activity coefficient of DL-threonine over the entire range of the DL-threonine and NaNO 3 studied.…”

“…The trace activity coefficient of DL-threonine in the aqueous solution of an electrolyte is the value of its activity coefficient when its molality approaches zero. To calculate the trace activity coefficient, all amino acid molality terms in equation (6) were set equal to zero. From figure 7, it can be seen that the trace activity coefficients of DL-threonine in the presence of NaCl and NaNO 3 are close to each other at low electrolyte molalities and slightly deviate at higher electrolyte molalities.…”

Activity coefficients of glycine in aqueous electrolyte solutions: experimental data for (H2O+ KCl + glycine) atT= 298.15 K and (H2O + NaCl + glycine) atT= 308.15 K

“…Most of the studies, which have reported the measurement of the activity coefficients of amino acids in aqueous electrolyte solutions using ion-selective electrodes, have used a cation ion-selective electrode only, against a reference electrode. (9,10,13) In these studies, the difference between the potentials of the ion-selective electrode and the reference electrode was calibrated with the mean ionic activity coefficient of the electrolyte in an aqueous electrolyte solution without the amino acid. Since in this method of measurement the effect of counter-ion of the electrolyte is neglected, it may lead to erroneous results.…”