Determination of Osmotic Coefficients of Aqueous Solutions Of
Indian Journal of Chemistry Vol. 41A, June 2002, pp. 1184-1187
Determination of osmotic coefficients of and can be used from 303 K to temperature below the aqueous solutions of polyhydroxylated freezing point of the solvent. compounds at various temperatures Determination of the osmotic coefficients of the aqueous solutions by VPO has been limited to a few 3 S 6 b papers . . Continuing our previous work ,7, the present Zuo-Ning Gao* a. b, Jin-Fu Li a & Xiao-Lin Wen note deals with aqueous solutions of glycol, glycerol, a Department of Chemistry, Ningxia University, Yinchuan 750021, P. R. China sucrose and glucose at various temperatures. b Department of Chemistry, Lanzhou University, Lanzhou Experimental 730001, P. R. China All measurements were carried out on aqueous Received 3 May 2001; revised II December 2001 solutions of different solutes (glycol, glycerol, sucrose and glucose) at 313, 323 and 333 K over the Osmotic coefficients of aqueous solutions of polyhydroxylated compounds such as glycol, glycerol, sucrose and glucose at concentration range of 0.0 - 2.0 mol kg" for glycol various temperatures over the concentration range of 0.0 - 2. 1 and sucrose, 0.0 - 2.1 mol kg" for glycerol and mol kg ·1 and 0.0 - 2.0 mol kg·1 have been determined, glucose, respectively, from which the osmotic respectively. Using a linear least-squares fitting routine, the coefficients were derived, using a knauer vapour osmotic coefficients have been fitted by a simple polynomial pressure osmometer Model 11.0 in combination with equation. It is found th at the relation between the experimental 8 results of th e molal osmotic coefficients KG = (o/m) NnCl / (v <1» Nne l • . • (2) Table I - The constants Ai fitted to Eq.(1) and their correlation coefficients R for the aqueous sodium chloride solution systems (reference substance) at the various temperatures T/K Ao A, A2 A3 A4 As R 313 218.4663 -259.9438 519.0930 -449.4234 179.7026 -26.9221 0.9756 323 240.2965 -265.4753 494.0028 -411.1611 160.8310 -23.7451 0.9899 333 259.8077 -280.4486 550.8686 -472.2478 187.2147 -27.8687 0.9648 lO Table 2 - The relation between <1>Rer , the reference value of the osmotic coefficient of the aqueous sodium chloride solution (reference substance) and, <1>Cah the calculated one from Eq.(2), and the calibration constants of the instrument at various temperature over the different concentration range mlmol Kg" 0.10 0.25 0.50 0.75 1.00 2.00 <1>Rer 0.932 0.922 0.924 0.931 0.941 0.992 313K <1>Cal 0.931 0.925 0.923 0.930 0.942 0.992 KG 95.1 95.0 95.0 94.9 95.1 95 .9 <1>Rer 0.931 0.921 0.924 0.932 0.942 0.995 323K <1>CaI 0.929 0.924 0.923 0.930 0.943 0.995 KG 107.5 107.8 108.1 108.5 108.1 106.9 <1>Rer 0.929 0.920 0.923 0.931 0.942 0.996 333K <1>CaI 0.928 0.923 0.922 0.930 0.943 0.996 KG 115.7 116.1 116.2 115.7 115.9 116.0 1186 INDIAN J CHEM, SEC A, JUNE 2002 Relationship from Eq.(4) can also be given by the sucrose and glucose are in a nsmg trend, and their curves of Figs 2 - 4. It can be seen from the Figs. 2 - temperature dependences exhibit their own 4 that the experimental values of the molar osmotic regularities. In the low concentration range, the coefficients of the aqueous solutions with different changes in osmotic coefficients with temperature are solutes at various temperatures over the different not noticeable, when the concentration range is l concentration range selected are good agreement with greater than 0.7714 mol kg· , the dependence of the that from the polynomial fitted from a linear least osmotic coefficient on temperature is of the order of squares routine. Table 3 gives the fitting constants AI, <1>313 > <1>323 > <1>333, that is to say, the osmotic A2, A3 and A4 obtained from Eq.(4) by linear least coefficients decreased with increase in temperature squares routine and their correlation constants R. and the decreasing trend is not much. At 313 and 323 The experimental results over the studied K over the low concentration range, the osmotic concentration range and at 313, 323 and 333 K show coefficients of aqueous sucrose and glucose solutions that the concentration dependence of the molar approach each other and appear to crisscross. osmotic coefficients of aqueous solutions of glycerol, However, over the higher concentration range, the 280r------, temperature dependence of the osmotic coefficients o 313 K exhibits <1> 313 > <1>323 > <1>333. Aqueous glycol solution 260 o 323 K 1.10 240 e- O 313K 0 323K C 1.08 Q) ·0 ~ Q) 0 1.06 U U ~ E 1.04 180 (/) 0 L.. ro 1.02 0 0.0 0.5 1.0 1.5 2.0 ~ m, mol kg-1 1.00 0.4 0.8 1.2 1.6 2.0 m, mol kg-1 Fig.l - The concentration dependence of (Glm )RZ32 of the aqueous sodium chloride solution systems at various temperatures. Fig.3 - The concentration dependence of the molar osmotic coefficients of the aqueous sucrose solution systems at various 1.06 r------, temperatures. o 313 K e- 1.05 o 313K C e- 1.04 Q) C ·0 1.04 Q) :E ·0 Q) ~ 1.03 o Q) U 1.03 0 U u u ~ :;::::; 1.02 E 1.02 0 Ul E o Ul L.. 0 ro L.. o 1.01 ro 1.01 ~ 0 ~ 0.0 0.3 0.6 0.9 1.2 1.5 1.8 1 0.0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 m, mol kg- m, mol kg-1 Fig.2 - The concentration dependence of the molar osmotic FigA - The concentration dependence of the molar osmotic coefficients of the aqueous glycerol solution systems at various coefficients of the aqueous glucose solution systems at various temperatures. temperatures. NOTES 1187 Table 3 - The constants Ai fitted from Eq.(4) and their correlation coefficients R for different aqueous solution systems at various temperatures Systems T/K AI A2 A3 A4 R 313 0.02035 0.00443 -0.00504 0.00129 0.9996 Glucose 323 0.02465 -0.00262 -0.00221 0.00096 0.9989 333 0.01244 0.00195 -0.00155 0.00050 0.9986 313 0.05333 -0.03237 0.02967 -0.00836 0.9993 Sucrose 323 0.05098 -0.01992 0.01161 -0.00240 0.9991 333 0.03192 0.00116 -0.00321 0.00110 0.9985 313 0.00441 0.02872 -0.01710 0.00381 0.9987 Glycerol 323 0.00953 0.02400 -0.02276 0.00657 0.9978 333 0.02404 -0.00609 -0.00426 0.00286 0.9979 system exhibits the properties of the ideal solution, Doctorate Initiation Foundation of Ningxia University that is, the relation between the osmotic coefficients (No.012202) are gratefully acknowledged. and its solution concentration are basically presented in a horizontal line (figure not shown). References The analyses of the experimental results indicated 1 Hill A Y, Proc Roy Soc, Series A, 9(1935)127. that the osmotic coefficients of aqueous glycol, 2 Burge D E, J phys Chern, 67( 1963)2590. glycerol, sucrose and glucose solution systems have 3 Peter Rohdewald & Gerhard Wesselmann, J chern no direct and obvious connections with the number of Research(s), (1979) 308. solute molecules in the aqueous solutions. 4 Sager! N H, J chern Eng Data, 29(1984)423. Comparing and analyzing the experimental results 5 Attwood D, Dickion N A & Mosquera Y, J phys Chern , and results from our previous wore, it was found that 91(1987)4203. between osmotic coefficients of aqueous solutions of 6 Zuoning Gao, Xiaolin Wen & lin lin, Huaxue TOllgbao(Ch ), polyhydroxylated compounds such as glucose, 4 (1996)35. sucrose and glycerol, and monomer glycol, polymer 7 Zuoning Gao, Xiaolin Wen & Hulin Li, Polish J Chern , 72( 1998)2346. 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