中文摘要：

测定了D-（-）-果糖、D-（＋）-葡萄糖、D-（＋）-半乳糖、D-（＋）-木糖和D-（-）-核糖五种糖的水溶液在不同质量摩尔浓度和不同温度下的介电常数（D）.结果表明,在一定温度下,这些糖的水溶液介电常数对数值都随糖浓度的增大而减小;在一定糖浓度时,介电常数值随温度升高而减小.果糖、葡萄糖、半乳糖和木糖水溶液的介电常数（D）随温度的变化均满足关系式：lgD=A1-B1（T-298.15）,而核糖水溶液则符合：lgD=A2-B2（T-298.15）＋C2（T-298.15）2.此外,这五种糖的水溶液的介电常数与摩尔分数（x）满足关系式：lg（D/D0）=-B3x.在相同温度和浓度时,介电常数的大小顺序通常为：水〉半乳糖-水〉果糖-水〉葡萄糖-水≥木糖-水（而核糖较特殊）.

英文摘要：

The dielectric constants （D） for aqueous solutions of D-（-）-fructose, D-（＋）-glucose, D-（＋）-galactose, D- （＋）-xylose, and D-（-）-ribose were measured at 278.15, 283.15, 288.15, 293.15, 298.15, 303.15, 308.15, and 313.15 K. Molalities of saccharides are at 0.2, 0.4, 0.6, 0.8, 1.0, and 1.2 mol ·kg^-1. The results indicated that the logarithmic values of dielectric constants for these saccharide-water solutions decreased with increasing molalities of saccharides and decreased also as the temperature rising. At given molalities, the relationship between dielectric constants and temperatures can be expressed by lgD=A1-B1（T-298.15） for fructose-water, glucose-water, galactose-water, and xylosewater solutions, and by lgD=A2-B2（T-298.15）＋C2（T-298.15）2 for ribose-water solution. At given temperatures, dependence of the dielectric constants on the mole fraction （x） can be described by lg（D/D0）=-B3x for all five saccharide-water solutions. At given temperatures and molalities, the dielectric constants are mostly in the order： water〉galactosewater〉fructose-water〉glucose-water ≥ xylose-water （there is not the order for ribose）.