混合溶剂中氨基酸解离热力学 5、278.15-318.15K下甘氨酸—25wt％葡萄糖—水体系

Dissociation Thermodynamics of Amino Acid in Mixed Solvents 5. Glycine in 25 mass% Glucose-Water over 278.15-318.15K

葡萄糖对水的性质和结构及氨基酸解离过程的影响的研究,对生物学、物理化学都有很大意义,作为我们以前工作的继续[1～3],本文选择葡萄糖—水作混合溶剂,测定无液接电池(A)和(B)的电动势Pt,H_2(g,101.325k Pa) HCl(m),Xwt％葡萄糖,(100-X)％水|AgCl-Ag (A)和Pt,H_2(g,101.325k Pa)|HGCl(m_1),G^+(m_2),Xwt％葡萄糖(100-X)％水 |AgCl-Ag (B)其中G^+代表中性甘氨酸,HGCl代表甘氨酸的盐酸盐,X=25％为葡萄糖在混合溶剂中所占的重量百分数。m_i为物质i的质量摩尔浓度。

This paper reports that the first thermodynamic dissociation constants of glycine in 25 mass% glucose-water mixed solvents have been determined at five temperatures over the range 278.15 to 318.15K. Its precise emf measurements was carried out in cell (A) without liquid junction: Pt, H_2 (g, 101.325kPa)|HGCl(m_1), G(m_2), in 25 mass% glucose-water|AgCl-Ag (A) This new method of polynomial approximation proposed on the basis of Pitzer's theory in our previous paper. As compared with traditional method, the results obtained agree within experimental error. The emf of cell (B) without liquid junction: Pt, H_2(g, 101.325kPa)|HCl(m_1), in 25 mass% glucose-water|AgCl-Ag (B) was measured with the standard emf of cell (A), E^0 , in the same mixed solvents at the same temperatures. The standard thermodynamic quantities for the first dissociation step of glycine in the mixed solvents and the standard transfer free energy of HCI have been calculated, and these results have been discussed.