折光率法测定对苯二酚在若干溶剂中不同温度下的浓度及饱和溶解度

Determination of Solubility of Hydroquinone in Several Solvents and Its Saturated Solubilities with Refractive Index Method

用折光率法测定了45℃、52℃、60℃三种温度下,对苯二酚在乙醇、正丁醇、正戊醇、异丙醚中浓度与折光率的关系以及饱和溶解度。首先进行了实验方法可靠性的验证,试验表明回收率在94.5%-102.4%之间,因而方法的可信度较高。最大溶解度平衡时间的测量表明:对于不饱和体系,振荡2小时,静置0.5小时,误差已小于0.1%;对于饱和溶解度,则必须振荡6-9小时,才能达到最大溶解度,这时误差小于0.02%。工作曲线表明,在这些溶剂中,对苯二酚的溶解度可大到接近23%,其折光率与浓度关系是一条较好的直线。与同一溶剂的苯酚工作曲线相比,相同浓度时对苯二酚的折射率较大,但相差不是很大,因而用平均工作曲线可以测量混合酚类的浓度,误差不大于2%。对于在线估计混合酚类的浓度,这是一个快速而有意义的方法。如果利用气相色谱估计得到对苯二酚与苯酚的比例,则利用内插工作曲线,用本方法测定的混合酚类的浓度误差可小到0.1%。对苯二酚在几种溶剂中的饱和溶解度是有用的热力学数据,尚未见过何处公开发表。

This paper is a continuation of refractive index method developing in our previous paper. It can be used to determine the contents of hydroquiinone in several solvents. The Saturated solubilities of hydroquinone in system ethanol、n -butyl alcohol、n -pentanol and diisopropyl ether at temperature 45℃ 52℃ 60℃ have been determined. Firstly, the experimental reliability was examined, the reclamation rate was determined and the maxium equilibrium time was searched. It shows that to unsaturated system, oscillating 2 hours and keeping still 0.5 hour are enough, but to saturated system, oscillating 6 - 9 hours is profitable, while the error of oscillating 2 hours is less than 0.1%. The higher the temperature, the shorter the equilibrium time. In working curves, it shows that the solubilities of hydroquinone in these four systems are as large as 23% mole fraction. So the refractive index is proportional to concentration. This method can be used in determination online. It can also be extended to determine contents of mixed phenols. There are large reference values for the choice of extration solvent. The saturated solubilities of hydroquinone in four solvents have not been published before.