Thermodynamic Quantities for the Ionization Reactions of Buffers

266 GOLDBERG, KISHORE, AND LENNEN
Values from literature
pK rH°/(kJ mol 1 ) T/K I Methods and comments Reference
Reaction „1…: H3LÄH2LÀ ¿H ¿
3.07 291.15 0 Electrochemical cell. 28KOL/BOS
3.08 298.15 0 Potentiometric titration. 28SIM
3.086 291.15 0 Electrochemical cell with liquid junction. The pK values given here, 29BJE/UNM
3.056 4.1 298.15 0
and which pertain to a molality standard state, were calculated from
the pK values given by Bjerum and Unmack 29BJE/UNM and
3.039 310.15 0
which pertained to the molarity scale. The value of rH° given here
was calculated from pKs measured at three temperatures.
3.200
3.176
278.15
283.15
0
0
Electrochemical cell—no liquid junction. The value of rH° given
here was calculated from pKs measured at several temperatures. The
49BAT/PIN
3.160
3.142
288.15
293.15
0
0
1 1 value rC p/(J K mol )131 was also calculated from the
temperature dependency of their 49BAT/PIN reported pKs.
3.128 4.17 298.15 0
3.116 303.15 0
3.109 308.15 0
3.099 313.15 0
3.097 318.15 0
3.095 323.15 0
3.08 298.15 0 Potentiometric titration. 51HEI
3.124 3.97 298.15 0 Potentiometric titration—glass electrode; calorimetry. 80ARE/CAL
3.098 310.15 0
3.132 298.15 0 Potentiometric titration—glass electrode. 90DAN/DER
3.191
3.145
283.15
293.15
0
0
Potentiometric titration—glass electrode. The value of rH° given
here was calculated from pKs measured at several temperatures. The
90DER/DES
3.128
3.114
5.40 298.15
303.15
0
0
1 1 value rC p/(J K mol )178 was also calculated from the
temperature dependency of their 90DER/DES reported pKs.
3.094 313.15 0
3.084 323.15 0
3.232
3.127 4.06
273.15
298.15
0
0
Electrochemical cell with liquid junction. The value of rH° given
here was calculated from pKs measured at several temperatures. The
97BEN/PAL
3.095
3.103
323.15
348.15
0
0
1 1 value rC p/(J K mol )162 was also calculated from the
temperature dependency of their 97BEN/PAL reported pKs.
3.135 373.15 0
3.186 398.15 0
3.255 423.15 0
3.456 473.15 0
Reaction „2…: H2LÄHL2À ¿H ¿
4.75 291.15 0 Electrochemical cell. 28KOL/BOS
4.74 298.15 0 Potentiometric titration. 28SIM
4.768 291.15 0 Electrochemical cell with liquid junction. The pK values given here, 29BJE/UNM
4.758 2.2 298.15 0
and which pertain to a molality standard state, were calculated from
the pK values given by Bjerum and Unmack 29BJE/UNM and
4.744 310.15 0
which pertained to the molarity scale. The value of rH° given here
was calculated from pKs measured at three temperatures.
4.837
4.813
273.15
278.15
0
0
Electrochemical cell—no liquid junction. The value of rH° given
here was calculated from pKs measured at several temperatures. The
49BAT/PIN
4.797
4.782
283.15
288.15
0
0
1 1 value rC p/(J K mol )178 was also calculated from the
temperature dependency of their 49BAT/PIN reported pKs.
4.769 293.15 0
4.761 2.45 298.15 0
4.755 303.15 0
4.751 308.15 0
4.750 313.15 0
4.754 318.15 0
4.757 323.15 0
4.66 298.15 0 Potentiometric titration. 51HEI
4.769 2.01 298.15 0 Potentiometric titration—glass electrode; calorimetry. 80ARE/CAL
4.758 310.15 0
4.751 298.15 0 Potentiometric titration—glass electrode. 90DAN/DER
4.823
4.789
283.15
293.15
0
0
Potentiometric titration—glass electrode. The value of rH° given
here was calculated from pKs measured at several temperatures. The
90DER/DES
4.777
4.766
3.85 298.15
303.15
0
0
1 1 value rC p/(J K mol )150 was also calculated from the
temperature dependency of their 90DER/DES reported pKs.
4.754 313.15 0
4.749 323.15 0
J. Phys. Chem. Ref. Data, Vol. 31, No. 2, 2002