稀有金属 2011,35(04),548-557

CsCl-PEG 400-H₂O三元体系在15,25和35℃时的等温溶解度、密度及折光率研究

康永宁 李淑妮 翟全国 蒋育澄 胡满成

摘 要：

采用半微量相平衡测定装置和高精度密度-折光率测定仪,精确测定了CsCl-PEG 400-H2O三元体系在15,25和35℃3个温度下不同组分百分比溶液的折光率和密度数据,通过关联密度和折光率数据获得了CsCl在上述温度下的等温溶解度。对饱和体系的溶解度研究表明:在同一温度下CsCl的溶解度随聚乙二醇质量分数的增加而减小;在不同温度下CsCl的溶解度随温度的升高而增大。采用经验方程lnS=A1+A2w2+A3w22+A4w23对饱和体系的溶解度进行了关联,效果较好。对不饱和体系的研究表明:当盐含量一定时,随着醇水比例的增加,体系的密度不断增大,折光率也随盐含量增加而增大;当醇水质量比一定时,体系的密度和折光率随盐含量的增加而增大,对不饱和体系的密度和折光率用经验方程Y=(A0+A1w2+A2w1+A3w1w2+A4w2w12)×exp[A5(w1/w3)+A6(w1/w3)2]进行拟合,拟合效果较好,同时给出了体系的盐析率曲线。本研究不仅为溶液化学提供了基础数据,也为混合溶液中盐和醇的分离纯化提供一种新的方法和思路,对CsCl进一步的应用、开发和研究具有一定的参考价值。

关键词：

CsCl;PEG400;溶解度;密度;折光率;

中图分类号： O642.42

作者简介：康永宁(1984-),女,陕西宝鸡人,硕士研究生;研究方向:重稀碱金属铷、铯盐的相化学(E-mail:hmch@snnu.edu.cn);

收稿日期：2010-08-07

基金：国家自然科学基金资助项目(20871079);

Equilibrium Solubility,Densities,and Refractive Indices for CsCl-PEG 400-H₂O Ternary System at 15,25 and 35 ℃

Abstract：

The phase equilibriums for CsCl-PEG 400-H2O ternary system were investigated at 15,25 and 35 ℃ respectively.The density and refractive index data of the solution with different percentage concentration were determined and used to calculate the isothermal solubility of CsCl at the three investigated temperatures.It was revealed that the solubility of CsCl decreased with the mass fraction of PEG 400 at the same temperature,and the solubility of CsCl increased with the system temperature increasing.The experience expression lnS=A1+A2w2+A3w22+A4w23 was satisfactorily used to correlated the solubility of the saturated ternary systems.The unsaturated systems were also studied.It was confirmed that when the salt content was constant,the density and the refractive index data increased continuously with the alcohol-water ratio increasing in this system.On the other hand,when the alcohol-water ratio was constant,the density and the refractive index data increased as the salt concentration increased.The experimental data of the density and the refractive index of the unsaturated ternary systems were fitted by the equation: Y=(A0+A1w2+A2w1+A3w1w2+A4w2w12)×exp[A5(w1/w3)+A6(w1/w3)2].At the same time,the salting-out curves of CsCl by PEG 400 were also obtained.The work not only provided the basic data for the solution chemistry,but also gave new insights into the separation and purification methods of salt and alcohol in mixed solution.It was also significant to further application,development and research of CsCl.

Keyword：

CsCl;PEG 400;solubility;density;refractive index;

Received： 2010-08-07

铷盐和铯盐是典型的稀有活泼碱金属, 容易分散于其他矿物质中, 很少形成独立的矿产, 由此给铷铯金属及其化合物的分离和提纯带来诸多困难。 近年来稀碱金属铷铯及其化合物在高科技领域的应用日益广泛 ^[1,2] , 已在无机盐分离纯化、 工农业生产、 生态环境保护、 材料制造和航空航天等方面 ^[3,4,5] 有广泛的应用, 因此对稀碱金属铷铯资源的开发, 开展对稀碱金属盐-混合溶剂体系相平衡的研究以及对稀碱金属盐的提纯开发利用, 都具有重要的意义。 Taboada等 ^[6] 将聚乙二醇加入到Na₂SO₄的水溶液中对Na₂SO₄进行了结晶提纯; Hull 等 ^[7] 曾将二乙烷加入到含有KI和KIO₃的水溶液中, 利用盐析效应使KIO₃析出并与KI分离; Greve等 ^[8] 利用脂肪醇和水的混合溶剂中对磷酸盐和硫酸盐进行了分离提纯。 本课题组已经深入研究过这类铷铯盐在简单脂肪醇水溶液中的相平衡情况: 岳涛等 ^[9,10,11,12] 研究了稀碱金属碳酸铷在纯水及无水乙醇中的等温平衡溶解度和Rb₂CO₃-C₂H₅OH-H₂O三元体系的等温溶解度数据; 李明华等 ^[13,14,15] 测定了不同温度下Rb₂SO₄-CH₃OH/C₂H₅OH-H₂O体系以及Rb₂SO₄-n-PrOH-H₂O体系的平衡溶解度情况; 张军等 ^[16,17,18] 研究了RbCl-C₂H₅OH-H₂O三元体系; 赵文霞等 ^[19,20] 研究了25和35 ℃时C₂H₅OH-RbCl-H₂O三元体系的相平衡关系并研究了25, 35和45 ℃时ROH-RbBr/Rb₂SO₄-H₂O (R=CH₃-, C₂H₅-, 1-C₃H₇-, 2-C₃H₇-)三元体系的相平衡; 孟梅等研究了CsCl-C₂H₅OH-H₂O三元体系在不同温度下的平衡溶解度, 并测定了该体系不饱和溶液40 ℃的分层临界组成 ^[21,22] ; 翟全国研究了0~50 ℃时Cs₂SO₄-ROH(R=CH₃-, C₂H₅-, n-C₃H₇-, i-C₃H₇-)-H₂O; Cs₂CO₃-ROH(R=CH₃-, C₂H₅-, n-C₃H₇-, i-C₃H₇-)-H₂O三元体系的相平衡关系 ^{[23,24,25,26,27,28,29]} ; 金利华等研究了CsCl-Cs₂SO₄-n-C₃H₇OH-H₂O四元体系在25 ℃时相平衡情况 ^[30] ; 郭海燕等研究了四元体系NaCl+RbCl+CH₃OH/C₂H₅OH/1-C₃H₇OH/2-C₃H₇OH+H₂O在15, 25, 35 ℃的相行为 ^[31] ; 王美霞等研究了25, 35和45 ℃时KCl+CsCl+ROH(R=CH₃-, C₂H₅-, 1-C₃H₇-, 2-C₃H₇OH)+H₂O四元体系及25 ℃时NaCl+CsCl+ROH(R=CH₃-, C₂H₅-, 1-C₃H₇-, 2-C₃H₇-)+H₂O体系的相平衡情况 ^[32] 。 本实验在利用课题组研究特色的基础上, 进一步创新实验方法, 给出了CsCl-PEG 400-H₂O三元体系的相平衡数据。 本文旨在探讨一种新型的研究、 分离和纯化稀碱金属盐方法的可行性, 为进一步研究、 应用和开发铷盐和铯盐提供必备的基本参考数据。

1 实 验

1.1 试剂和仪器

1.1.1 试剂

氯化铯: CsCl (江西锂厂, 纯度99.5%), 在500 ℃下煅烧2 h, 冷却后装瓶, 放在干燥器中备用; 聚乙二醇(PEG 400国药集团化学试剂有限公司AR); 无水乙醇(国药集团化学试剂有限公司 分析纯AR); 整个实验用水均为二次蒸馏水。

1.1.2 仪器

10 ml注射器; 真空干燥箱(DZ-2BC, 天津泰斯特仪器有限公司); 自制半微量相平衡测定装置 ^[33] ; 密度折光仪(DMA4500-RXA170, Anton Paar); 电子天平 (FA1104, 上海精科天平厂)。

1.2 实验操作

1.2.1 密度/折光率标准曲线的绘制

由于此类溶液的折光率与其盐和醇的质量百分含量存在以下经验关系 ^[34,35] :

nD=a₀+a₁w_CsCl+a₂w_PEG (1)

ρ=b₀+b₁w_CsCl+b₂w_PEG (2)

其中nD为溶液的折光率, a₀, a₁, a₂, b₀, b₁和b₂均为方程的系数, w_CsCl为溶液中CsCl的质量分数, w_PEG为溶液中PEG 400的质量分数。 联立方程(1)和(2), 通过测量溶液的密度和折光率数据, 计算获得体系的溶解度。 通过标准曲线获得方程的系数, 标准曲线的制作如下: 配制三组CsCl浓度一定(依次为0%, 3%, 6%), PEG 400浓度依次增加的标准溶液, 测定其在25 ℃时的标准溶液的折光率和密度数据, 以PEG 400的质量分数为横坐标, 溶液的折光率和密度为纵坐标作图即可。

1.2.2 饱和体系相平衡的测定

饱和CsCl-PEG 400-H₂O三元体系在实验温度范围内均没有出现为分层现象, 其具体操作如下: 首先在10 ml的平衡管中配制一系列总质量约为6 g, 不同质量比例的聚乙二醇和水的混合溶液, 加入适当过量的CsCl, 振荡直到有固体剩余, 然后将平衡管置于半微量相平衡的转盘上, 恒温水浴控温精度为±0.1 ℃, 达到预定温度后, 恒温转动48 h, 确保每个平衡管中均有适量晶体存在, 否则需要补充盐, 重新进行上述过程, 恒温静置约24 h, 最后从平衡管中取出一定量的饱和溶液, 稀释, 测定其25 ℃下的密度和折光率。 将所得密度和折光率数据代入上述方程即可求算出原溶液中的盐含量和醇含量。

1.2.3 非饱和体系的密度和折光率测定

为获得CsCl-PEG 400-H₂O三元体系全面的理化性质数据, 同时测量了该体系在非饱和状态下的密度和折光率。 不饱和体系的方法与饱和体系的研究过程基本相同, 仅是确保整个实验过程中所有样品管中均无CsCl固体存在。 从测得的密度和折光率数据可以看出, 在非饱和态溶液中当醇水质量比一定时, 体系密度折光率随盐含量的增加而增大。

2 结果与讨论

2.1 密度/折光率标准曲线

图1和2为CsCl-PEG 400-H₂O三元体系的折光率和密度标准曲线, 根据该标准曲线计算获得参数a₀, a₁, a₂, b₀, b₁和b₂, 可将方程(1)和(2) 转化为:

nD=1.33242+0.13273w_PEG+0.078667w_CsCl (3)

ρ=0.99696+0.16536w_PEG+0.77600w_CsCl (4)

图1 CsCl-PEG 400-H2O三元体系在25 ℃时的折光率标准曲线 Fig.1 Refractive index calibration curves for CsCl-PEG 400-H2O ternary system at 25 ℃

图2 CsCl-PEG 400-H2O三元体系在25 ℃时的密度标准曲线 Fig.2 Density calibration curves for CsCl-PEG 400-H2O ternary system at 25 ℃

将方程(3)和(4)联立求解, 可得到w_CsCl和w_PEG关于密度和折光率的表达式:

w_CsCl=(0.13273ρ-0.16536nD+0.08800247)/0.08999015 (5)

w_PEG=(0.776nD-0.0786667ρ-0.95553037)/0.08999015 (6)

值得注意的是该密度折光率标准曲线有一定的适用范围, 即w_PEG<0.10, w_CsCl<0.06, 这是由于该方程为适用于稀溶液的经验方程, 在该范围内盐和醇的质量百分含量与密度及折光率均呈现性良好的线性关系, 所以在测定样品溶液的折光率和密度之前, 需将原始样品溶液浓度稀释至这一范围内。

2.2 饱和体系的溶解度、 密度及折光率

三元体系CsCl-PEG 400-H₂O 在15, 25和35 ℃的数据分别见表1中。 对应不同温度下CsCl在混合溶剂中溶解度变化趋势见图3, 由图3可以看出: 从该表中可以看出: 同一温度下随着聚乙二醇质量分数的增加, CsCl 在混合溶剂中的溶解度逐渐减小, 体系的折光率也逐渐降低。 本实验结论与文献报道的其它体系中相一致 ^[36,37] 。 在所研究CsCl-PEG 400-H₂O三元体系中, 饱和溶液的溶解度用方程(7)进行拟合 ^[38] :

lnS=A₁+A₂w₂+A₃w₂²+A₄w₂³ (7)

其中S为盐的溶解度(每100 g混合溶剂中溶解的盐的质量); w₂代表聚乙二醇在溶液中的质量分数; A₁, A₂, A₃, A₄均为拟合参数, 将实验结果与

表1 CsCl-PEG 400-H2O 三元体系在15, 25和35 ℃的密度及折光率数据Table 1 Mass fraction, density (ρ), and refractive index (nD) solubility the CsCl+PEG 400+H2O systems at 15, 25 and 35 ℃

wPEG	wCsCl	ρ/(g·cm-3)	nD	wPEG	wCsCl	ρ/(g·cm-3)	nD
15 ℃
0.0000	0.6460	1.02020	1.33475	0.3819	0.3350	1.01168	1.33593
0.0303	0.6109	1.01821	1.33473	0.4831	0.2752	1.00873	1.33586
0.0768	0.5700	1.01705	1.33485	0.5989	0.2160	1.00854	1.33661
0.1281	0.5225	1.01414	1.33476	0.7519	0.1484	1.00549	1.33639
0.2028	0.4643	1.01372	1.33512	0.8672	0.1030	1.00693	1.33792
0.2867	0.4004	1.01426	1.33578
25 ℃
0.0000	0.6593	1.01862	1.33476	0.3868	0.3482	1.01105	1.33574
0.0470	0.6197	1.01749	1.33473	0.4933	0.2808	1.00951	1.33609
0.0892	0.5784	1.01806	1.33503	0.6124	0.2161	1.00889	1.33678
0.1404	0.5357	1.00931	1.33413	0.7411	0.1532	1.00682	1.33693
0.2095	0.4825	1.01338	1.33506	0.8782	0.0966	1.00604	1.33754
0.2915	0.4203	1.01428	1.33574
35 ℃
0.0000	0.6667	1.03544	1.33638	0.3933	0.3649	1.04649	1.34393
0.0442	0.6477	1.04031	1.33725	0.5067	0.2907	1.04265	1.34573
0.0880	0.6068	1.03650	1.33726	0.6298	0.2184	1.03413	1.34611
0.1429	0.5537	1.02161	1.33582	0.7661	0.1456	1.02755	1.34686
0.2099	0.4971	1.01429	1.33518	0.9091	0.0843	1.02701	1.35015
0.2852	0.4343	1.01515	1.33583

图3 CsCl-PEG 400-H2O 三元体系(15, 25, 35) ℃时的平衡溶解度 Fig.3 Solubility (S) in terms of molality for the CsCl-PEG-H2O system at (15, 25, and 35) ℃ as a function of the PEG 400 mass fraction in the salt-free solvent

文献值比较, 数据列于表2中 ^[39,40] , 从差值可以看出密度折光率法较好, 所研究体系的拟合参数值及相对标准偏差δ列于表 3, 整个实验的相对标准偏差均小于1.0%。

根据CsCl-PEG 400-H₂O三元体系等温平衡溶解度分析结果, 将CsCl在纯水中的溶解度与其在混合溶剂中的溶解度之差与CsCl在纯水中的溶解度相比, 即可得到聚乙二醇对CsCl的盐析率R, R-w_PEG的关系(图4)。 从图中可见, 聚乙二醇对CsCl的盐析率在15, 25和35 ℃时相差不是很大。

表2 15, 25和35 ℃下CsCl在纯水中的溶解度Table 2Solubility for CsCl in pure water at 15, 25 and 35 ℃(%, mass fraction)

t/℃	Reference	Experiment	Gap
15	64.91[39]	64.60	0.31
25	65.63[40]	65.93	-0.30
35	66.99[39]	66.67	0.32

表3饱和溶液溶解度数据用方程(7)拟合所得参数及相对标准偏差Table 3Values of parameters of equation (7) for saturated system

t/℃	A1	A2	A3	A4	δ
15	-3.2283	9.8110	-12.3	5.913	0.0154
25	-3.1933	9.5909	-11.9	5.62	0.0159
35	-3.1313	9.1102	-10.8	4.924	0.0143

图4 15 ℃ (a), 25 ℃ (b)和35 ℃ (c)时聚乙二醇对CsCl的盐析率曲线 Fig.4 Salting-out percentage of PEG towards CsCl at 15 ℃ (a), 25 ℃ (b) and 35 ℃ (c)

2.3 不饱和体系溶液密度和折光率

表4~6为实验测定的CsCl-PEG 400-H₂O三元体系在15, 25和35 ℃下的不饱和溶液的折光率和密度数据, 图5为CsCl-PEG 400-H₂O体系在15 ℃时不饱和溶液密度和折光率随盐含量变化曲线图, 其他温度下图形类似, 从图中可以看出: 盐含量一定时, 随着醇水比例的增加, 体系的密度不断增大, 折光率也随盐含量增加而增大; 当醇水质量比一定时, 体系密度随盐含量的增加而增大。 其他温度下的三元体系不饱和溶液密度和折光率含量变化曲线与25 ℃类似。 将所得不饱和溶液数据用以下参数方程 ^[39] 进行了关联:

其中Y代表不饱和体系的密度或折光率, A_i为拟合参数, w₁, w₂, w₃分别为醇、 盐、 水在溶液中的质量分数, 方程拟合的结果与相对标准偏差δ的数值列于表7中, 从相对标准偏差可以看出拟合结果比较理想。

图5 三元体系CsCl+PEG 400+H2O 15 ℃不饱和溶液密度和折光率随醇含量变化曲线 Fig.5 Density (ρ) and refractive index (nD) for the undersaturated system at 25 ℃

表4 三元体系CsCl+PEG 400+H2O 15 ℃时不饱和溶液折光率和密度数据Table 4 Density (ρ) and refractive index (nD) for the CsCl+PEG 400+H2O undersaturated system at 15 ℃

wPEG	wCsCl	nD	ρ/(g·cm-3)	wPEG	wCsCl	nD	ρ/(g·cm-3)
wPEG/wH2O=0.1111
0.1001	0	1.34660	1.01571	0.0933	0.0681	1.35199	1.07075
0.0988	0.0120	1.34750	1.02495	0.0921	0.0784	1.35284	1.07957
0.0977	0.0238	1.34843	1.03432	0.0901	0.0985	1.35455	1.09714
0.0964	0.0351	1.34930	1.04343	0.0885	0.1145	1.35593	1.11146
0.0943	0.0572	1.35111	1.06156
wPEG/wH2O=0.4286
0.2999	0	1.37489	1.05163	0.2849	0.0501	1.37855	1.09193
0.2970	0.0105	1.37565	1.05991	0.2821	0.0597	1.37923	1.10021
0.2937	0.0209	1.37643	1.06815	0.2797	0.0677	1.37976	1.10753
0.2907	0.0309	1.37711	1.07607	0.2740	0.0869	1.38107	1.12283
0.2878	0.0405	1.37782	1.08413	0.2712	0.0966	1.38203	1.13211
wPEG/wH2O=1.0001
0.5000	0	1.40521	1.08847	0.4766	0.0468	1.40811	1.12639
0.4960	0.0081	1.40571	1.09490	0.4657	0.0686	1.40960	1.14494
0.4920	0.0161	1.40619	1.10126	0.4587	0.0825	1.41032	1.15680
0.4842	0.0316	1.40712	1.1138	0.4804	0.0393	1.40770	1.12009
wPEG/wH2O=2.3336
0.6999	0	1.43391	1.11657	0.6752	0.0355	1.43620	1.14617
0.6958	0.0062	1.43435	1.12154	0.6719	0.0402	1.43646	1.15007
0.6918	0.0117	1.43467	1.12614	0.6642	0.0512	1.43720	1.15959
0.6876	0.0177	1.43498	1.13106	0.6598	0.0575	1.43763	1.16493
0.6796	0.0291	1.43582	1.14072
wPEG/wH2O=8.9990
0.8999	0	1.45838	1.12858	0.8861	0.0178	1.45958	1.14388
0.8967	0.0037	1.45867	1.13172	0.8771	0.0254	1.46008	1.15023
0.8899	0.0086	1.45896	1.13565	0.8742	0.0289	1.46037	1.15319
0.8900	0.0110	1.45915	1.13807	0.8709	0.0324	1.46060	1.15651
0.8868	0.0146	1.45937	1.14107	0.8666	0.0372	1.46087	1.16082

表5 三元体系CsCl+PEG 400+H2O 25 ℃时不饱和溶液折光率和密度数据Table 5 Density (ρ) and refractive index (nD) for the CsCl+PEG 400+H2O undersaturated system at 25 ℃

wPEG	wCsCl	nD	ρ/(g·cm-3)	wPEG	wCsCl	nD	ρ/(g·cm-3)
wPEG/wH2O=0.1111
0.0856	0.1437	1.35735	1.13551	0.0544	0.4563	1.39257	1.52424
0.0749	0.2513	1.36772	1.24653	0.0498	0.5018	1.39951	1.60325
0.0665	0.3349	1.37698	1.34782	0.0460	0.5402	1.40584	1.67557
0.0598	0.4017	1.38502	1.43939	0.0428	0.5726	1.41157	1.74178
wPEG/wH2O=0.4286
0.2654	0.1155	1.38162	1.14389	0.1815	0.3950	1.40844	1.46677
0.2379	0.2071	1.38948	1.23415	0.1683	0.4392	1.41380	1.53593
0.2156	0.2814	1.39653	1.31810	0.1568	0.4775	1.41894	1.59869
0.1970	0.3431	1.40284	1.39592	0.1467	0.5109	1.42334	1.65667
wPEG/wH2O=0.1000
0.4573	0.0853	1.40836	1.15262	0.3410	0.3181	1.42616	1.39873
0.4214	0.1572	1.41341	1.21944	0.3206	0.3588	1.42834	1.45039
0.3908	0.2185	1.41776	1.28215	0.3025	0.3949	1.43376	1.50386
0.3641	0.2717	1.42210	1.34209
wPEG/wH2O=2.3334
0.6629	0.0530	1.43382	1.15223	0.5470	0.2186	1.44581	1.31144
0.6295	0.1006	1.43738	1.19532	0.5240	0.2514	1.44811	1.35096
0.5993	0.1438	1.44056	1.23659	0.5030	0.2814	1.45006	1.38632
0.5719	0.1830	1.44320	1.27618
wPEG/wH2O=8.9957
0.8833	0.0185	1.45676	1.13633	0.8094	0.1006	1.46238	1.21077
0.8677	0.0358	1.45779	1.15137	0.7960	0.1155	1.46331	1.22508
0.8523	0.0529	1.45911	1.16651	0.7831	0.1298	1.46455	1.23939
0.8375	0.0694	1.45990	1.18175	0.7716	0.1427	1.46535	1.25212
0.8231	0.0853	1.46135	1.19616

表6 三元体系CsCl+PEG+H2O 35 ℃时不饱和溶液折光率和密度数据Table 6 Density (ρ) and refractive index (nD) for the CsCl+PEG+H2O undersaturated system at 35 ℃

wPEG	wCsCl	nD	ρ/(g·cm-3)	wPEG	wCsCl	nD	ρ/(g·cm-3)
wPEG/wH2O=0.1112
0.1001	0	1.34397	1.00548	0.0930	0.0701	1.34941	1.06515
0.0988	0.0123	1.34490	1.01872	0.0919	0.0807	1.35025	1.07434
0.0975	0.0247	1.34584	1.02823	0.0909	0.0913	1.35108	1.08337
0.0964	0.0363	1.34673	1.03658	0.0899	0.1015	1.35198	1.09239
0.0953	0.0477	1.34764	1.04688	0.0897	0.1125	1.35280	1.10119
0.0941	0.0591	1.34850	1.05495
wPEG/wH2O=0.4286
0.3000	0	1.37138	1.04195	0.2815	0.0616	1.37589	1.09156
0.2969	0.0108	1.37222	1.05032	0.2786	0.0713	1.37632	1.09946
0.2935	0.0216	1.37304	1.05866	0.2758	0.0806	1.37716	1.10759
0.2900	0.0334	1.37377	1.06834	0.2730	0.0899	1.37775	1.1153
0.2874	0.0420	1.37437	1.07528	0.2698	0.1007	1.37882	1.12537
0.2843	0.0521	1.37524	1.08277
wPEG/wH2O=0.9962
0.5000	0	1.39992	1.07417	0.4748	0.0503	1.40337	1.11553
0.4956	0.0088	1.40098	1.08171	0.4709	0.0583	1.40416	1.12224
0.4811	0.0170	1.39979	1.08640	0.4670	0.0660	1.40441	1.12866
0.4871	0.0258	1.40167	1.09541	0.4632	0.0737	1.40453	1.13704
0.4829	0.0342	1.40131	1.10035	0.4594	0.0812	1.40621	1.14399
0.4788	0.0423	1.40311	1.10886
wPEG/wH2O=2.3337
0.7000	0	1.42816	1.10042	0.6760	0.0343	1.43052	1.12868
0.6960	0.0058	1.42853	1.10508	0.6721	0.0398	1.43108	1.13376
0.6918	0.0118	1.42910	1.11000	0.6685	0.0450	1.43146	1.13803
0.6877	0.0175	1.42950	1.11486	0.6645	0.0507	1.43226	1.14367
0.6839	0.0230	1.42976	1.11934	0.6542	0.0658	1.43277	1.15610
0.6797	0.0290	1.43019	1.12456
wPEG/wH2O=8.9953
0.900	0	1.45174	1.11236	0.8813	0.0206	1.45345	1.12873
0.8965	0.0039	1.45199	1.11529	0.8782	0.0241	1.45406	1.12998
0.8937	0.0069	1.45201	1.11821	0.8753	0.0274	1.45412	1.13603
0.8907	0.0104	1.45224	1.12061	0.8725	0.0304	1.45434	1.13846
0.8872	0.0142	1.45223	1.12379	0.8692	0.0341	1.45478	1.14119
0.8845	0.0172	1.45327	1.12699

表7 不饱和溶液密度和折光率数据用方程(8)拟合所得参数及相对标准偏差Table 7Values of parameters of Eq.(8) for density and refractive index of the undersaturated ternary systems CsCl+PEG 400+H2O at three temperatures

t/℃	A0	A1	A2	A3	A4	A5	A6	δ
Density
15	0.9944	0.8444	0.2057	0.0627	0.5028	-0.0109	0.0006	0.0016
25	0.8660	1.4747	0.3973	-0.4878	0.3749	-0.0206	0.0012	0.0128
35	0.9900	0.8198	0.1788	0.3093	-0.0844	-0.0065	0.0003	0.0009
Refractive index
15	1.3242	0.3061	0.1994	-1.5097	2.0384	-0.0106	0.0008	0.0029
25	1.3197	0.1413	0.1555	0.0734	0.0138	0.0004	0.00008	0.0012
35	1.3356	-0.0630	0.0942	1.1569	-1.3202	0.0102	-0.0008	0.0020

3 结 论

随着科技的发展, 稀碱金属的无机盐应用越来越广泛, 对其纯度的要求越来越高。 但这类盐大多溶解度较大, 且溶解度随温度变化不明显, 使用其他方法来纯化往往不理想。 本文采取密度折光法获得了CsCl-PEG 400-H₂O三元体系在不同温度下的平衡溶解度, 并对饱和溶液和不饱和溶液的相关数据进行拟合, 得到较好的结果, 为溶液化学的应用研究提供了新方法、 新思路。

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