The acidic dissociation constant of N-(2-acetamido)-iminodiacetic acid monosodium (ADA) has been determined at 12 temperatures from 278.15 to 328.15 K by electromotive-force (emf) measurements of hydrogen-silver chlor...The acidic dissociation constant of N-(2-acetamido)-iminodiacetic acid monosodium (ADA) has been determined at 12 temperatures from 278.15 to 328.15 K by electromotive-force (emf) measurements of hydrogen-silver chloride cells without liquid junction. At 298.15 K, the value of the dissociation constant (pK2) is 6.8416 ± 0.0004. In response to the need for new physiological pH standards, buffer solutions of NaADA and its disodium salt, Na2ADA would be useful for pH control in the biological region of pH 6.5 to 7.5. The pK2 values over the experimental temperature range are given as a function of the thermodynamic temperature (T) by the equation pK2 = 2943.784/T - 47.05762 + 7.72703 ln T. At 298.15 K, standard thermodynamic quantities for the dissociation process have been derived from the temperature coefficients;ΔH° = 12,252 J·mol-1, ΔS° = -89.9 J·K-1·mol-1 and = -148 J·K-1·mol-1. The results are interpreted and compared with those of structurally related derivatives of GLYCINE.展开更多
Values of the second thermodynamic dissociation constant pK2 of the protonated form of monosodium 1,4-piperazinediethanesulfonate (PIPES) have been determined at twelve different temperatures in the temperature range ...Values of the second thermodynamic dissociation constant pK2 of the protonated form of monosodium 1,4-piperazinediethanesulfonate (PIPES) have been determined at twelve different temperatures in the temperature range from (278.15 to 328.15) K including the body temperature 310.15 K by measurement of the electromotive-force for cells without liquid junction of the type: Pt (s), H2 (g), 101.325 kPa|Na-PIPES (m1) + Na 2-PIPES (m2) + NaCl (m3)|AgCl (s), Ag (s), where m1, m2 and m3 indicate the molalities of the corresponding species at 1 atm = 101.325 kPa in SI units. The pK2 values for the dissociation of Na-PIPES are represented by the equation: pK2 = -1303.76/T + 48.369 - 6.46889 lnT with an uncertainty of ± 0.001. The values of pK2 for Na-PIPES were found to be 7.1399 ± 0.0004 at 298.15 K and 7.0512 ± 0.0004 at 310.15 K, respectively, and indicate that this buffer would be useful as pH standard in the range of physiological application. Standard thermodynamic quantities for the acidic dissociation process of Na-PIPES have been derived from the temperature coefficients of the pK2. These values are compared with those of structurally related N-substituted PIPERAZINE and TAURINE at 298.15 K.展开更多
Thermodynamic dissociation constants pKa of 2,2-bis(hydroxymethyl)-2,2’,2”-nitrilotriethanol have been determined at 12 temperatures from (278.15 to 328.15) K including the body temperature 310.15 K by the electromo...Thermodynamic dissociation constants pKa of 2,2-bis(hydroxymethyl)-2,2’,2”-nitrilotriethanol have been determined at 12 temperatures from (278.15 to 328.15) K including the body temperature 310.15 K by the electromotive-force measurements (emf) of hydrogen-silver chloride cells without liquid junction of the type: Pt(s), H2(g), 101.325 kPa|BIS-TRIS (m) + BIS-TRIS·HCl (m)| AgCl(s), Ag(s), where m denotes molality. The pKa values for the dissociation process of BIS-TRIS·H++ H2O = H3O+ + BIS-TRIS given as a function of T in Kelvin (K) by the equation pKa = 921.66 (K/T) + 14.0007-1.86197 ln(T/K). At 298.15 and 310.15 K, the values of pKa for BIS-TRIS were found to be 6.4828 ± 0.0005 and 6.2906 ± 0.0006 respectively. Thus buffer solutions composed of BIS-TRIS and its hydrochloride would be useful as secondary pH buffer standards and for control of acidity in the pH range 6 to 8. At 298.15 K the thermodynamic functions G°, H°, S° and Cp° for the dissociation process of BIS-TRIS·H+ are G°=37,005 J·mol-1, H° = 28,273 J·mol-1, S°= 29.3 J·K-1·mol-1 and Cp° = 36 J·K-1·mol-1. These results are compared with the dissociation of protonated bases structurally related to BIS-TRIS·H+.展开更多
In order to investigate the property and concentration dependence of dissociation and hydrolysis of polyelectrolytes,acrylic acid-sodium acrylate copolymers with various degree of neutralization were prepared by addin...In order to investigate the property and concentration dependence of dissociation and hydrolysis of polyelectrolytes,acrylic acid-sodium acrylate copolymers with various degree of neutralization were prepared by adding calculated amounts of sodium hydroxide into the aqueous solutions of a poly(acrylic acid) sample,and the pH values of the solutions covering a wide concentration range were measured for each copolymer at 25℃.It was found that the pH values of the solutions of a copolymer with degree of neutralization of 0.96 kept constant and equaled to 9.80 as c>0.001 mol/L.For another copolymer with degree of neutralization of 0.30,the pH values of its solutions remained constant and equaled to 6.25 as c<0.001 mol/L.These two copolymers may serve as polymeric buffer reagents which couldn’t penetrate through semi-permeable membranes in the corresponding concentration regions.展开更多
The authors have undertaken the determination of pH values for one buffer solution of TES without NaCl and nine buffer solutions with NaCl yielding an ionic strength I = mol.kg-1. similar to that of blood. These buffe...The authors have undertaken the determination of pH values for one buffer solution of TES without NaCl and nine buffer solutions with NaCl yielding an ionic strength I = mol.kg-1. similar to that of blood. These buffer solutions have been evaluated in the temperature range of 5℃ to 55℃ using an extended version of the Debye-Hückel equation. The pH values are reported using 1) the Debye-Hückel extension of the Bates-Guggenheim convention in the tempera- ture range 5℃ to 55℃ and 2) with and without liquid junction correction at 25℃ and 37℃. These TES buffer solutions are recommended as secondary standard references for pH measurements in the range of pH 7.2 to 7.5 for physiological application with an ionic strength of I = 0.16 mol.kg-1.展开更多
文摘The acidic dissociation constant of N-(2-acetamido)-iminodiacetic acid monosodium (ADA) has been determined at 12 temperatures from 278.15 to 328.15 K by electromotive-force (emf) measurements of hydrogen-silver chloride cells without liquid junction. At 298.15 K, the value of the dissociation constant (pK2) is 6.8416 ± 0.0004. In response to the need for new physiological pH standards, buffer solutions of NaADA and its disodium salt, Na2ADA would be useful for pH control in the biological region of pH 6.5 to 7.5. The pK2 values over the experimental temperature range are given as a function of the thermodynamic temperature (T) by the equation pK2 = 2943.784/T - 47.05762 + 7.72703 ln T. At 298.15 K, standard thermodynamic quantities for the dissociation process have been derived from the temperature coefficients;ΔH° = 12,252 J·mol-1, ΔS° = -89.9 J·K-1·mol-1 and = -148 J·K-1·mol-1. The results are interpreted and compared with those of structurally related derivatives of GLYCINE.
文摘Values of the second thermodynamic dissociation constant pK2 of the protonated form of monosodium 1,4-piperazinediethanesulfonate (PIPES) have been determined at twelve different temperatures in the temperature range from (278.15 to 328.15) K including the body temperature 310.15 K by measurement of the electromotive-force for cells without liquid junction of the type: Pt (s), H2 (g), 101.325 kPa|Na-PIPES (m1) + Na 2-PIPES (m2) + NaCl (m3)|AgCl (s), Ag (s), where m1, m2 and m3 indicate the molalities of the corresponding species at 1 atm = 101.325 kPa in SI units. The pK2 values for the dissociation of Na-PIPES are represented by the equation: pK2 = -1303.76/T + 48.369 - 6.46889 lnT with an uncertainty of ± 0.001. The values of pK2 for Na-PIPES were found to be 7.1399 ± 0.0004 at 298.15 K and 7.0512 ± 0.0004 at 310.15 K, respectively, and indicate that this buffer would be useful as pH standard in the range of physiological application. Standard thermodynamic quantities for the acidic dissociation process of Na-PIPES have been derived from the temperature coefficients of the pK2. These values are compared with those of structurally related N-substituted PIPERAZINE and TAURINE at 298.15 K.
文摘Thermodynamic dissociation constants pKa of 2,2-bis(hydroxymethyl)-2,2’,2”-nitrilotriethanol have been determined at 12 temperatures from (278.15 to 328.15) K including the body temperature 310.15 K by the electromotive-force measurements (emf) of hydrogen-silver chloride cells without liquid junction of the type: Pt(s), H2(g), 101.325 kPa|BIS-TRIS (m) + BIS-TRIS·HCl (m)| AgCl(s), Ag(s), where m denotes molality. The pKa values for the dissociation process of BIS-TRIS·H++ H2O = H3O+ + BIS-TRIS given as a function of T in Kelvin (K) by the equation pKa = 921.66 (K/T) + 14.0007-1.86197 ln(T/K). At 298.15 and 310.15 K, the values of pKa for BIS-TRIS were found to be 6.4828 ± 0.0005 and 6.2906 ± 0.0006 respectively. Thus buffer solutions composed of BIS-TRIS and its hydrochloride would be useful as secondary pH buffer standards and for control of acidity in the pH range 6 to 8. At 298.15 K the thermodynamic functions G°, H°, S° and Cp° for the dissociation process of BIS-TRIS·H+ are G°=37,005 J·mol-1, H° = 28,273 J·mol-1, S°= 29.3 J·K-1·mol-1 and Cp° = 36 J·K-1·mol-1. These results are compared with the dissociation of protonated bases structurally related to BIS-TRIS·H+.
文摘In order to investigate the property and concentration dependence of dissociation and hydrolysis of polyelectrolytes,acrylic acid-sodium acrylate copolymers with various degree of neutralization were prepared by adding calculated amounts of sodium hydroxide into the aqueous solutions of a poly(acrylic acid) sample,and the pH values of the solutions covering a wide concentration range were measured for each copolymer at 25℃.It was found that the pH values of the solutions of a copolymer with degree of neutralization of 0.96 kept constant and equaled to 9.80 as c>0.001 mol/L.For another copolymer with degree of neutralization of 0.30,the pH values of its solutions remained constant and equaled to 6.25 as c<0.001 mol/L.These two copolymers may serve as polymeric buffer reagents which couldn’t penetrate through semi-permeable membranes in the corresponding concentration regions.
文摘The authors have undertaken the determination of pH values for one buffer solution of TES without NaCl and nine buffer solutions with NaCl yielding an ionic strength I = mol.kg-1. similar to that of blood. These buffer solutions have been evaluated in the temperature range of 5℃ to 55℃ using an extended version of the Debye-Hückel equation. The pH values are reported using 1) the Debye-Hückel extension of the Bates-Guggenheim convention in the tempera- ture range 5℃ to 55℃ and 2) with and without liquid junction correction at 25℃ and 37℃. These TES buffer solutions are recommended as secondary standard references for pH measurements in the range of pH 7.2 to 7.5 for physiological application with an ionic strength of I = 0.16 mol.kg-1.
