乙醇-水混合溶剂中氨基酸解离热力学性质

Thermodynamic Properties of Dissociation of Amino Acid in Mixed Solvents of Ethanol and Water

在乙醇和水混合溶剂中恒定乙醇质量分数ｘ＝０．２，应用经典的电动势方法测定无液体接界电池的电动势： Ｐｔ，Ｈ２（１．０１３ × １０５ Ｐａ）｜ＨＣｌ（０．０１ ｍ），乙醇（ｘ），Ｈ２Ｏ（１－ｘ）｜ＡｇＣｌ－Ａｇ（Ａ） Ｐｔ，Ｈ２（１．０１３ × １０５Ｐａ）｜ ＧＨＣｌ（ｍ１），Ｇ±（ｍ２），乙醇（ｘ），Ｈ２Ｏ（１－ｘ）｜ ＡｇＣｌ－Ａｇ（Ｂ）其中ＧＨＣｌ代表甘氨酸的盐酸盐，根据电池（Ａ）和（Ｂ）的电动势，用传统的Ｄｅｂｙｅ－Ｈｕｃｋｅｌ外推方法和该文提出的多项式逼近法，确定了甘氨酸在 ２７８．１５～３１８．１５ Ｋ范围内 ５个温度下的一级热力学解离常数，两种方法得出的结果在实验误差范围内一致．计算了甘氨酸一级解离过程的其它热力学参数．

The primary thermodynamic dissociation constants of glycine were studied by means of EMF measurements of the cell without liquid junction at different temperatures from 278. 15 to 318. 15 K in the 0. 2 mass fraction of ethanol-water mixed solvent. The first dissociation constants of glycine were calculated by using the polynomial approach proposed on the basis of Pitzer's electrolytic solution theory and traditional extrapolation on the basis of extended Debye-Huckel equation. The results show that both methods are in agreement with each other. The thermodynamic quantities of the first dissociation process of glycine in the mixed solvent were calculated and the results were discussed.