Temperature Effect on the Liquid-Liquid Equilibria for Some Aliphatic Alcohols + Water + K 2 CO 3 Systems Alireza Salabat* and Mahmod Hashemi Chemistry Department, Arak University, P.O. Box 38156-879, Arak, Iran The liquid-liquid equilibrium (LLE) data were measured for the systems ethanol + water + K 2 CO 3 , 1-propanol + water + K 2 CO 3 , 2-propanol + water + K 2 CO 3 , and 2-methyl-2-propanol + water + K 2 CO 3 at (298.15, 308.15, and 318.15) K. A two-parameter equation was used for the correlation of the experimental tie-line data. Good agreement was obtained with the experimental tie-line data with this model. Introduction The salt in mixed solvent plays an important role in sci- entific research and the chemical industry, such as recycling of an organic solvent in a mixed-solvent system, design of extractors, separation of mixtures, biological process, etc. In recent years, research groups have focused on the measure- ments of phase equilibrium data for this systems. 1-8 In our previous works, liquid-liquid equilibrium (LLE) of some aqueous alcohols containing inorganic salts were investigated. 5,9 As far as we know, there is no reported data on the LLE for aliphatic alcohol and water mixtures composed with potassium carbonate at different temperatures. Due to the salting-out effect, adding K 2 CO 3 into the alcohols + water systems leads to an organic-rich phase with negligible salt and a water-rich phase with negligible alcohol, so a large amount of water can be separated from the alcohols by simple and efficient phase separation. In this research, the LLE data for the ternary systems ethanol + H 2 O + K 2 CO 3 , 1-propanol + H 2 O + K 2 CO 3 , 2-propanol + H 2 O + K 2 CO 3 , and 2-methyl-2-propanol + H 2 O + K 2 CO 3 at (298.15, 308.15, and 318.15) K are reported. A two-parameter equation was successfully applied for the correlation of the experimental LLE data. Experimental Section Materials. The alcohols and potassium carbonate were obtained from Merck (alcohols GR, min 99.8 % and potassium carbonate GR, min 99.5 %). All chemicals were used without further purification. The stock solution of potassium carbonate has prepared with triple distilled water. Apparatus and Experimental Procedure. Experimental ap- paratus and aqueous two-phase equilibrium experiment were described previously. 5 A glass vessel, volume 50 cm 3 , was used to carry out the phase equilibrium determinations. It had an external jacket in which water at constant temperature was circulated from a thermostat. The temperature was controlled to within ( 0.1 K. The binodal curves only for 298.15 K were determined by the cloud point method. An aqueous potassium carbonate solution of known concentration was titrated with alcohol, until the solution turned turbid. The composition of the mixture was followed by mass using an analytical balance with a precision of ( 1 × 10 -7 kg. For the determination of the tie-lines, alcohols, salt, and water were mixed to give a defined point in the two-phase region of the phase diagram. The mixture was stirred for 2 h and then allowed to settle overnight. After equilibrium was achieved, phases were sepa- rated with care and analyzed for water, alcohol, and salt concentration. Analytical Methods. The concentrations of various alcohols and water were determined by gas chromatography with thermal conductivity detector manufactured by Shimadzu (Shimadzu 6A). The column and injector temperatures were (453 and 473) K, respectively, for all systems. The uncertainty in the mass percent for the top and bottom phase analyses was less than ( 0.1 for water or alcohol. The water content of some samples was also measured with Kyoto mks-210 Karl Fischer instrument. The titration method used for the determination of potassium carbonate using titro processor Metrohm 686. Determinations made for solutions of known salt concentrations indicated that this method is very accurate and reproducible. For the analysis of the bottom phase, 0.1 g of the samples was used, and for the * Corresponding author. Tel: +98-861-2777401. Fax: +98-861-2767306. E-mail: a-salabat@araku.ac.ir. Table 1. LLE Data for the Ethanol (1) + Water (2) + K2CO3 (3) Ternary System at Three Temperatures organic phase aqueous phase 100 w1 100 w2 100 w3 100 w1 100 w2 100 w3 T ) 298.15 K 44.82 53.04 2.14 9.28 70.61 20.11 58.60 40.4 1.00 3.97 67.52 28.51 68.74 30.68 0.58 1.90 63.50 34.60 76.82 22.76 0.35 1.38 59.82 38.80 82.01 17.73 0.25 0.80 55.14 44.06 87.17 12.73 0.15 0.34 50.16 49.50 T ) 308.15 K 48.07 49.40 2.40 7.12 68.67 24.21 59.29 38.99 1.20 4.34 65.16 30.50 68.61 30.34 0.60 2.56 61.18 36.26 79.29 20.49 0.22 1.85 56.42 41.73 82.11 17.76 0.15 0.96 52.89 46.15 87.63 12.27 0.10 0.41 49.46 50.13 T ) 318.15 K 45.01 51.84 3.40 7.20 67.72 25.08 61.22 37.59 1.15 4.57 63.60 31.83 70.16 28.67 0.50 3.21 60.35 36.44 77.02 22.82 0.25 2.28 57.40 40.32 82.27 17.61 0.15 1.10 52.96 45.94 87.76 12.14 0.10 0.83 50.54 48.63 1194 J. Chem. Eng. Data 2006, 51, 1194-1197 10.1021/je050515b CCC: $33.50 © 2006 American Chemical Society Published on Web 05/05/2006