Densities have been determined for ternary aqueous solutions containing glycine, ethylene glycol or glycerol(cosolvent), with mass fractions of the polyols in cosolvent-water mixtures ranging from 0 to 0.50. The apparent molar volumes, the limiting partial molar volumes and hydration numbers of glycine zwitterion have been calculated. The transfer volumes from water to polyol-water mixtures have been obtained and discussed in terms of the structural hydration interaction model. The results obtained have been compared with that in ethanol-water mixtures. It is concluded that the magnitude of enhancement effect on volume is somewhat related to the number of OH groups on alcohol molecules. However, the most important factor that influences volumes is the structural shapes of hydration shells of alcohol molecules. The unusual enhancement effect on volume in ethanol-water mixtures is considered to be related to the fact that the micro-structure of the mixtures is heterogeneous and discontinuous.%利用精密数字密度计测定了甘氨酸分别在不同组成的乙二醇-水和丙三醇-水混合溶剂中的密度，计算了甘氨酸的表观摩尔体积、极限偏摩尔体积和理论水化数 .根据结构水合作用模型讨论了迁移偏摩尔体积的变化规律，并与乙醇-水体系作了比较 . 结果表明，甘氨酸分子在醇-水混合溶剂中增体积效应的大小与醇分子所含 OH基数目的多少有关，但最直接也是最重要的影响因素是其水合壳层的结构形态 . 乙醇-水体系中的增体积效应特别显著与该溶剂结构变化上的微观不均匀性和不连续性有关 .
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