Experimental investigations of the h eterogeneous system:
ferric chloride-water-isopropyl ether, at 20° C, were carried out. From
the experimental results the equilibrium compositions of the phases,
tie lines in the two-liquid-phase region and the isothermal curve
of the three-component system were determined

D. Maljković

M. Branica

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CR 0 AT IC A CHEMIC A ACT A 38 (1966) 65 CCA-408 542.61 :541.121 Note Equilibria of Liquid Phases in the Ternary System: Ferric Chloride - Water - Isopropyl Ether D. MaljkoviC* and M. Branica Department of Physical Ch emistry, Institute »Ruder Boskovic«, Zagreb and Faculty of Technology, University of Zagreb, Sisak, Croatia, Yugoslavia Received January 16, 1966. Experimental investigations of the heterogeneous system: ferric chloride-water-isopropyl ether, at 20° C, were carried out. From the experimental results the equilibrium compositions of the phases, tie lines in the two-liquid-phase region and the isothermal curve of the three-component system were determined. INTRODUCTION In the course of a study of the extraction of ferric chloride by isopropyl ether from aqueous solutions of hydrogen chloride, it appeared advisable to undertake investigations of the ternary system: ferric chloride-water-isopropyl ether in order to determine the influence of fer r ic chloride on the mutual solubility of isopropyl ether and water. This system is one of the lateral planes of the tetrahedral model which represents the four-component system ferric chloride-hydrochloric acid-water-isopropyl ether. EXPERIMENTAL Materials. The isopropyl ether, Fluka c. p ., was purified by treatment with saturated ferrous sulfate solution followed by sodium hydroxide solution. After washing it with water, it was distilled and the middle fraction (b. p. 66.8°-67.8° C at 743.5 mmHg) was collected for further use. Isopropyl ether which is prepared in this way contained 1.63 mg. H20 /ml. Anhydrous ferric chloride, T. Schuchardt, was 98 per cent pure. Other chemicals used were of analytical reagent grade. Methods of analysis. Iron and isopropyl ether from the aqueous phase and iron and water in the ethereal phase were determined directly. The third component in both phases was found by a difference. For the determination of iron in quantities greater than 1 millimole complexometric titration (Titriplex III with 2-oxi-5-sulfo-benzoic acid1) was used. For quantities less than 1 millimole the ultraviolet light absorption of samples was measured. The ethereal phase was analysed for water by the Karl Fischer titration method2 as modified by Laurene.3 The analysis resulted in a consi-derable problem, since very small quantities were present in the aqueous phase. The method which w as proposed by Tuck• was applied to solutions containing ferric chloride. Centrifuge tubes with calibrated narrow necks were used. The height of the separated ether (over solubility) after neutralization was measured with a catheto-meter. The solubility of isopropyl ether in the final solution in the tube containing approximately 12 ml. was 19.57 mg. In a number of samples quantities of ether were * Taken in part from the M.Sc. thesis of D. Maljkovic, submitted to the Faculty of Science, University of Zagreb, 1965. 66 D. MALJKOVIC AND M. BRANICA under the sensitivity limit of m ethod. When greater quantities of iron were present, the determination was more difficult because of precipitat ion of iron hydroxide. The equilibrium ratio of volumes of the phases were determined in a graduated separation funnel (the accuracy was + 0.05 ml.). Density determinations of the phases were made with 10 ml. pycnometers.-Procedure. Systems were prepared in separation funnels. The funnels were shaken vigo-rously for 15 seconds and placed in a water bath thermostat held by automatic control at 20.0 ± 0.05° C. The shaking was repeated, always in the same manner, during one hour in intervals of fifteen minutes. The analyses of the phases were performed after one hour, i.e. when equilibria were attained. Apparatus. The separations were made in 25 ml. and 50 ml. separation funnels having a calibr&ted stem. The zero of the calibration was at the drain cock. A thermostat Towson & Mercer, Croydon, an apparatus for electrometric titration of water Baird & Tatlock, London and a spectrophotometer Hilger Uvispek were used. RESULTS AND DISCUSSI ON Series of compositions of coexisting phases at 20° C were determined by analytical method. The influence of ferric chloride on the mutual solubility of isopropyl ether and water is very small. These results could be expected because the principal factor effecting an increase of solubility of ether in aqueous solutions was the formation of the species Et-H+ which occurs only in strong acid solutions.5 It is well known that the percentage of extraction of ferric chloride with isopropyl ether is practically nil if the initial concentration of hydrochloric acid is less than two molar6• The data obtained from the analyses are presented in the Table. The mole percentages are schematically plotted on the shortened ternary diagram in Fig. 1, and on an enlarged scale in Fig. 2. In Figs. 1 and 2 the area above the uppermost tie line is the three-phase region, i.e. all compositions represented by points inside this region separate TABLE I Molarity of the Heterogeneous System: FeCl 3-H20-Isopropyl Ether Initial volume ratio IPE*-H20 was 1 : 1, at 20° C FeC13 initial 3.45 3.10 2.26 2.15 1.28 1.00 0.62 0.43 0.33 0.18 0.07 0.02 Aqueous phase -~-----FeCla I IPE* I H20 2.71 0.10 49.74 2.67 + 49.34 2.03 + 50.60 2.00 + ! 50.71 1.21 + 52.53 0.97 + 52.92 0.62 + 53.67 0.42 + 54.53 0.33 + 54.66 0.18 + 54.88 0.061 + 55.11 0.020 + 55.17 I + The actual quantity of !PE• is less than 19.57 mg. * !PE = isopropyl ether Ether phase FeC13 IPE* 0.046 7.02 0.020 7.06 0.001 7.06 0.000 7.05 0.000 7.08 0.000 7.07 0.000 7.08 0.000 7.05 0.000 7.06 0.000 7.06 0.000 7.07 0.000 7.04 0.34 0.31 0.21 0.20 0.22 0.24 0.25 0.26 0.26 0.27 0.26 0.26 EQUILIBRIA OF LIQUID PHASES 67 //\ 2 \ 100 % H20 so% 100 O/o IPE Fig. 1. T ernary system F eCb-HoO - !PE in the section of t riangle diagram, at 200 C. Isothermal curve and tie lines of the system a re plotted in molar percents . into one solid and two liquid phases with compositions A (aqueous phase) and B (ethereal phase). The obtained composition of the aqueous phase at point A is 5.16 mol 0/o FeCL,, 0.19 mol '0/o IPE and 94.65 mol '0/o H"O; and that of ethereal phase at point B is 0.64 mol 'O/o FeCL., 94. 72 mol O/o IPE, and 4.64 mol 0/o H 20. The composition of the solid phase (ferric chloride and/or hydrates) wa~ not reported in this paper because it is out of the scope of the extraction system studied. The area under the uppermost tie line is the heterogeneous region of two liquid phases, ·where tie lines connect the points representing the compositions of coexisting liquid phases on the isothermal curve. 95% 97 Ofo 99% IPE Fig. 2. Experimental p oints representing equilib rium of the coexisting liquid phases is shown in sections on t h e enlarged triangle diagram. In Fig. 2 experimental points r epresenting equilibrium compositions of coexistent phases in the enlarged section of the triangle diagram with corres-ponding tie lines are shown. On the basis of the results experimentally obtained it may be supposed that the solubility of water in the ether phase decreases markedly to a minimum at initial concentration of 2.15 M ferric chloride. It increases slowly when the initial concentration of ferric chloride is further decreased. This influence of ferric chloride on the mutual solubility of water and ether is similar to the one of hydrochloric acid in the system HC1-H20-iso-propyl ether.7 63 D . MALJKOVIC AND M. BRANICA Acknowledgment. The authors are grateful to Miss J. StanCin for some technical assistance in this work. REFERENCES 1. G. Schwarzenb a ch, Die Komplexometrische Titration, F . Enke Verlag, Stutt-gart., 1960, pp. 72-73. 2. J. Mitch e 11 and D. M. Smith, Aquametry, Interscience Publ., New York, 1948. 3. H. A. Lauren e, Anal. Chem. 24 (1952) 1496. 4. D. C. Tuck, Anal. Chim. Acta 20 (1950) 159. 5. B. V. Ne k r as o v and V. V. 0 rs yank in a, J. Gen. Chem. (USSR) 11 (1941) 573. 6. R. W . Dodson, G. J . Forney, and E. H. Swift, J. Am. Chem. Soc. 58 (1936) 2573. 7. D. E. Cam be 11, A. H. Lauren e, and H. M. C 1 ark, J. Am. Chem. Soc. 74 (1952) 6193. IZVOD ' Ravnotefa tekucih faza u' trokomponentnom sistemu: zeljezni (Ill) klorid-voda--izopropilni eter D. Maljkovic i M. Branica Iz\Tsena su ispitivanja ravnoteze tekucih faza h eterogenog trokomponentnog sistema: zeljezni (III) klorid-voda-izopropilni eter kod 20° C. Na osnovu eksperimen-talnih rezultata nadeni su ravnotezni sastavi faza, vezne linije u dvofaznom podrucju i izotermna krivulja topivosti sistema. INSTITUT »RUDER BOSKOVIC« ZAGREB Primlj eno 16. sijecnja 19Go. 

Equilibria of Liquid Phases in the Ternary System: Ferric Chloride - Water - Isopropyl Ether

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