Application of Osmotic Coefficient Theory of Electrolyte in Metrology of Physical Chemistry Quantities Including Water Activity
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摘要: 渗透系数(ϕ)反映了电解质溶液中溶剂偏离理想溶液的程度。渗透系数可采用蒸气压法和电动势法等多种方法测定。美国国家标准局统计了已发表的数据,以每种电解质溶液的多套科学数据的平均值,作为该电解质溶液的渗透系数的标准值,并给出了渗透系数的标准偏差。该渗透系数的标准数据以德拜-休克尔公式的形式表达,方便使用者代入电解质溶液的质量摩尔浓度计算对应的渗透系数。渗透系数可用于计算电解质溶液的水分活度、冰点和渗透压摩尔浓度,从而为相关特性量标准溶液定值,分别用于校准相关特性量的测量仪器。在众多的电解质中,最常用的是氯化钠。国际标准和国家标准规定的上述特性量的标准值,和根据渗透系数标准数据计算得到的结果一致性良好。根据渗透系数标准数据计算相关特性量的标准值,能够通过渗透系数标准数据间接地溯源至蒸气压和电动势等量值的SI单位。Abstract: Osmotic coefficient (ϕ) is a measure of the deviation of the solvent of electrolyte from the ideal solution. ϕ was usually determined by the manometric method and the electromotive force method. National bureau of standard of United States of America published the reference value of osmotic coefficient equal to the average of many scientific data and its standard deviation based on the statistics. This reference data was expressed as the Debye-Hückel equation. When the molality of the electrolyte was introduced in the equation, and thus the corresponding osmotic coefficient was deduced. ϕ can be used to calculate the water activity, freezing point depression and osmotic pressure concentration of the solution of electrolyte, and thus the reference solution of these quantities were determined and then used to calibrate the instrument of these quantities. Sodium chloride was the most commonly used electrolyte. The reference values specified by the related international or national standard were well consistent with the results calculated using the reference data of ϕ. The reference values of related physical chemistry quantities calculated using the reference data of ϕ were traceable to SI units of vapor pressure or potential of the electromotive force indirectly.
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Key words:
- metrology /
- osmotic coefficient /
- water activity /
- freezing point depression /
- osmolality /
- reference material
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表 1 NaCl渗透系数原始数据的来源
Table 1. Source of the data of osmotic coefficient of NaCl
编号 测量方法 作者 年代 1 电势法 Allmand, Polack[2] 1919 2 电势法 Harned[3] 1929 3 电势法 Harned, Nims[4] 1932 4 电势法 Brown, MacInnes[5] 1935 5 电势法 Sakong, Huang 1962 6 电势法 Lebed, Aleksandrov 1964 7 电势法 Wilke, Schrӓnkler 1932 8 电势法 Janz, Gordon[6] 1943 9 电势法 Caramazza 1960 10 电势法 Getman[7] 1920 11 电势法 Haas, Jellinek 1932 12 双温法 Stokes[8] 1947 13 扩散法 Harned[9] 1959 14 蒸气压法 Negus 1922 15 蒸气压法 Pearce, Nelson[10] 1932 16 蒸气压法 Olynyk, Gordon[11] 1943 17 蒸气压法 Petit[12] 1965 18 露点法 Hepburn[13] 1928 19 等压法 Robinson, Sinclair[14] 1934 20 等压法 Scatchard, Hamer[15] 1938 21 等压法 Robinson[16] 1939 22 等压法 Janis, Ferguson[17] 1939 23 等压法 Robinson[18] 1945 表 2 NaCl溶液水分活度的计算值
Table 2. Calculated value of water activity of NaCl aqueous solution
质量摩尔浓度
(mol/kg)质量
百分数ISO 21807推荐
的水分活度[19]ϕ标准
数据根据ϕ标准
数据计算得到的
水分活度0.1 0.58% 0.9966 0.933 0.9966 0.2 1.15% 0.9934 0.924 0.9934 0.3 1.72% 0.9900 0.921 0.9901 0.4 2.28% 0.9868 0.921 0.9868 0.5 2.84% 0.9835 0.922 0.9835 0.6 3.39% 0.9802 0.923 0.9802 0.7 3.93% 0.9769 0.926 0.9769 0.8 4.47% 0.9736 0.929 0.9736 0.9 5.00% 0.9702 0.932 0.9702 1.0 5.52% 0.9669 0.936 0.9668 1.2 6.55% 0.9601 0.944 0.9600 1.4 7.56% 0.9532 0.953 0.9531 1.6 8.55% 0.9461 0.963 0.9460 1.8 9.52% 0.9389 0.973 0.9388 2.0 10.46% 0.9316 0.984 0.9315 2.2 11.39% 0.9242 0.995 0.9241 2.4 12.30% 0.9166 1.007 0.9166 2.6 13.19% 0.9089 1.020 0.9089 2.8 14.06% 0.9011 1.032 0.9011 3.0 14.92% 0.8932 1.046 0.8931 3.2 15.75% 0.8851 1.059 0.8851 3.4 16.58% 0.8769 1.073 0.8768 3.6 17.38% 0.8686 1.087 0.8685 3.8 18.17% 0.8600 1.101 0.8600 4.0 18.95% 0.8515 1.116 0.8514 5.0 22.61% 0.8068 1.192 0.8068 6.0 25.97% 0.7598 1.270 0.7599 表 3 不饱和盐溶液的溶质、浓度、渗透系数和水分活度
Table 3. Solute, concentration, osmotic coefficient and water activity of unsaturated solution of salts
溶质 质量摩尔浓度(mol/kg) 渗透系数 水分活度 LiCl 13.481 2.851 0.250 LiCl 8.533 2.251 0.500 NaCl 5.953 1.266 0.762 NaCl 5.209 1.208 0.797 NaCl 4.029 1.118 0.850 NaCl 2.825 1.034 0.900 NaCl 1.487 0.957 0.950 表 4 NaCl溶液的质量分数、质量摩尔浓度和冰点下降值
Table 4. Mass fraction, molality and freezing point depression of NaCl solution
质量摩尔浓度
(mol/kg)质量
百分数GB5413.38
规定的冰点[22]
(mK)ϕ标准
数据根据ϕ标准数据
计算得到的冰点
(mK)0.1165 0.676% 400 0.9305 403 0.1189 0.690% 408 0.9302 411 0.1315 0.763% 450 0.9288 454 0.1465 0.849% 500 0.9274 505 0.1495 0.866% 510 0.9271 515 0.1501 0.870% 512 0.9270 517 0.1525 0.884% 520 0.9268 525 0.1555 0.901% 530 0.9266 536 0.1585 0.918% 540 0.9264 546 0.1616 0.935% 550 0.9261 556 0.1637 0.948% 557 0.9260 563 0.1767 1.022% 600 0.9251 607 表 5 NaCl溶液的质量摩尔浓度、质量分数和渗透压摩尔浓度
Table 5. Molality, mass fraction and Osmolality of NaCl solution
1kg溶剂所含的NaCl
质量(g/kg)质量摩尔浓度
(mol/kg)质量百分数 药典规定的渗透压摩尔
浓度(mOsmol/kg)[22]ϕ标准数据 根据ϕ标准数据计算的渗透
压摩尔浓度(mOsmol/kg)3.087 0.0528 0.3077 %100 0.9431 99.6 6.260 0.1071 0.6221 %200 0.9318 199.6 9.463 0.1619 0.9374 %300 0.9261 299.9 12.684 0.2170 1.2525 %400 0.9229 400.6 15.916 0.2723 1.5667 %500 0.9212 501.8 19.147 0.3276 1.8787 %600 0.9204 603.1 22.380 0.3829 2.1890 %700 0.9202 704.8 -
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