Four Ternary Liquid Systems Involving Monochorobenzene J
J
PHASE EQUILIBRIA AND TIE LINE DATA JOHN S. PEAKE AND KENNETH E. THOMPSON, JH.' Qepartment qf Chemistry, Indiana University, Rloornington, Znd.
T
0 DATE little attention has been devoted to the systenis involving chlorobenzene. This may be due in part to its inability t o form hydrogen bonds and hence its position among the Class V liquids of Ewell, Harrison, and Berg ( 2 ) . An interest in chlorobenzene and its possibilities as a selective solvent for solutes of different types, led to the present investigation. Only two references in the literature present data on systems involving chlorobenzene. Othmer, White, and Trueger (8) determined equilibrium and tie line data for the system acetonechlorobenzene-water. Trimble and Frazer (9) studied the system acetone-ethylene glycol-chlorobenzene, obtaining tie lines as well as equilibrium data. Morello and Poffenberger (6) indicate in their review article dealing with solvent extraction equipment that unpublished data exist for the system chlorobenzene-phenol-water. The four systems chosen for study involve chlorobenzene and water as competing solvents. Acetic and dichloroacetic acids were chosen a s weak and moderately strong acids, respectively. Pyridine and n-butylamine were chosen as weakly basic substances. Equilibrium and tie line data are preRented for these systems.
chi s. The fraction boiling in the range Ti" to 78" C. was colgcted. Titration of a sample of the purified material with standard hydrochloric acid using methyl red as indicator, indicated a purity of 99.9%. material had an indicated .. $he original purity of 97.4%. Pyridine. Commercial p ridine was dried over solid sodium hydroxide and then distillehY through a column havine five theofetical plates. The colorless proauct was further purified by converting it to thecrystalline compound, di yridino-zinc chloride, and then decomposing the complex, aceorzing to the method of Heap, Jones, and Speakman (4). The material prepared by the decomposition of the complex had a boiling range of 114.5' t o 115 'C. Attem t s t o prepare high-purity pyridine by two other methods p r o v e 8 less satisfactory. One involved the potassium ferrocyanide-pyridine complex and the other the mercuric chloridepyridine complex. The potassium ferrocyanide complex was very difficult to filter without excessive loss. The mercuric chloride complex was found to be difficult to decompose. APPARATUS
The apparatus used for determining the equilibrium curve consisted essentially of a titration cell, burets with elongated capillary tips, a constant temperature bath with B circulating pump, and a suitable light source. The titration cell was of borosilicate glass in the form of a large test tube having a jacket PIJRIFICATIOI\'OF MATERIALS around the lower two thirds of it. Water from the constant Water. Ordinary laboratory distilled water wm used without temperature bath was circulated through this jacket. This further purification-. maintained the temperature of the cell contents a t a constant Chlorobenzene, The chlorobenzene used in this investigation value but permitted unrestricted observation of the contents of w a ~dried over phosphorus pentoxide and then distilled. The the inner vessel. By having the cell between the light source and middle fraction boiling at 131 a C. ww collected and the remainder was discarded. Its refracthe observer, it was possible t.ive index, TZD, was 1.5205. to detect very easily the apAcetic acid. Mallinpearance or disappearance ckrodt glacial acetic acid of a phase. A piece of (99.595'0) was used without further purification. cardboard with a slit in it Dichloroacetic acid. placed over the light source Eastman Kodak Co. "Pracreduced glare and made obtical" dichloroacetic acid was distilled under vacuum servation very easy. The and the colorless fraction contents of the cell were boiling a t 95" t o 96' C./17 continuously agitated by mm. was collected for use, This boiling range was in means of a motor-driven good agreement with the glass stirrer. The burets value of 95" to 96" C./17.4 had long, capillary tips bent mm. for pure dichloroacetic so as t o permit them t o acid given by Doughty and Black (1). enter the rubber stopper of n-Butylamine. The best the titration cell on either g r a d e of n - b u t y l a m i n e side of the tube containing made b the Eastman Kodak was dried by the ball bearing for the means of metallic potassium shaft of the stirrer. With chips. T h e . dried liquid this ariangement it was was t h e n d i s t i l l e d o v e r freshly c u t potassium unnecessary t o change ;&GI burets as in the appaH . 2 0 1Prasent address, E. I. du Figure 1. System: Chlorobenzene-Water-Acetic Acid ratus used by Smith and Pont de Nemoura & Co., NewBonner (19) burgh, N. Y. 25" C. Isotherm
80.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44, No. 10
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r CsHg CI
Figure 2.
\
HZ0
System: Chlorobenzene-Water-Dichloroacetic Acid 25" C. Isotherm METHODS
The method of determining the mutual solubility curve was that described by Taylor ( 7 ) . Tie lines were obtained by direct analysis of the equilibrium layers formed by a mixture of the three components in known ratio. Weighed samples from each of the conjugate layers nere analyzed by titration with a suitable reagent. Standard sodium hydroxide solution m-ith phenolphthalein as indicator was used for the systems involving acetic and dichloroacetic acids. Oning t o the high selectivity of water, the presence of the chlorobenzene phase gave no trouble. Standard hydrochloric acid solution with methyl red indicator was used for the pyridine and n-butylamine systems. Dilution of the chlorobenzene layer with ethanol to give a homogeneous phase during the titrations gave sharp and reliable end points. A check of the reliability of the data is provided by the coincidence with the tie line of the point representing the over-all composition and those on the equilibrium curve representing the coexisting
TABLEI. SYSTEBI:CHLOROBENZENE-WATER-ACETIC ACID
Figure 3.
System: Chlorobenzene-Water-n-Butylamine 25" C. Isotherm
phases. The tie line data were further correlated by the method of Hand (3). RESULTS
The data for the four systems are summarized in Tables I to IV- and are shown graphically in Figures 1 to 4. Values for the plait points of the distribution curves were estimated by the method discussed by Treybal, Weber, and Daley (8). The plots for this estimation are not shoyn; the values are given in the tables. DISCUSSIOR- OF RESULTS
The tie line data for the acetic acid and dichloroacetic acid systems with chlorobenzene and water show the anticipated selectivity of water for the acid component and the expected increase in selectivity with increase of acid strength.
TABLE11. SYSTEM:CHLOROBENZENE-WATER-DICHLOROACETIC .&ID
A.
Chlorobenzene, Wt. % 0.08 0.10 0.12 0.30 0.47 0.67 0.86 1.31 1.48 1.86 2.50 3.12 4.24 5.91 7.73 10.25
D a t a for Solubility Curve a t 25' C. ChloroAcetic Acid, Water, benzenr, Acetic Acid, Wt. % w t . % Wt. % JTt. % 13.40 67.83 19.05 66.02 25.50 62.54 31.00 58.94 32.30 58.06 36.50 54.99 43.60 49.92 48.90 45.75 41.46 54,40 62.00 35.35 27.11 71.55 21.96 77.25 15.86 83.80 91.23 8.60 0.00 99.95
YO
Water, Tt.
%
18.77 14.93 11.96 10.06 9.64
8.51 6.48 5.35 4.14 2.65 1.34 0.79 0.34 0.17 0.06
B. D a t a for Tie Lines a t 25O C. Over-all Composition CeHbCl Acetic acid 9.00 16.60 23.00 28.48 37.32 41.03 47.20 56.36 62.85 Estimated plait point 51.4 44.0
Hz0
4.6
Wt. % ' Acetic Acid CeHaCllayer Hz0 layer 0.72 1.72 3.13 4.32 7.60 8.42 12.03 17.11 21.80
A.
Data. for Solubility Curve a t 25O C . ,
Chloro- DichioroChloro- Dichlorobenzene acetic Acid, Water, benzene, acetic Acid, Wt. % ' Wt. % wt. % wt.% W t . % 0.08 99.92 53.08 61.40 0.15 49.50 54.10 46,94 0.29 44.70 47.90 1.20 41.10 42.01 2.55 34.95 40.82 4.42 30.82 38.03 6.18 31.80 26.25 9.30 12.20 25.87 23.40 15,57 20.78 17.93 17.82 19.93 13.00 22.50 16.30 8.43 26.90 14.45 0.00 29.00 13.90 B. D a t a for Tie Lines a-t Over-all Composition CeHaCl CHChCOzH 47.30 46.10 41.05 37.61 34.40 31.35 28.75 26.03 23.00 Estimated plait point 68.2 27.3
HzO 42.90 40.81 37.10 34,15 31.20 28.40 2G. 10 23.60 20,85 4.5
Water, Wt. % 11.62 10.60 9.36 9.00 8.09 7.68 7.12 5.83 4.13 2.47 1.50 0,57 0.05
Wt. % Dichioroacetic Acid CaHaCl layer Hz0 layer 1.23 17.82 1.25 25.14 1.87 36.10 44.10 2.03 2.61 51.10 3.02 56.65 3.43 60.25 5.04 63.20 7.65 64.60
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TABLE111. SYSTEM: CHLOROBENZENE-WATER-+BUTYLAMINE A.
Chlorobenzene, Wt. %
*
Data for Solubility Curve a t 25" C. Chloron-Butylamine, Water, benzene, n-But lamine, Wt.% Wt. % W t . % %
99.95 87.00 83.10 74.25 66.10 57.30 56.50 53.20 45.50 37.50 34.90 30.85
0.05 1.41 2.96 7.50 12.60 18.90 19.55 22.20 28.25 35.10 37,80 41.55
w"c.
Water, Wt.%
26.45 22.85 17.80 13.80 10.25 7.30 6.33 4.90 3.52 0.23
27.55 26.90 25.90 23.80 21.60 19.30 18.42 16.70 14.48 10.57
0.08
0.00
46.00 50.25 56.30 62.40 68.15 73.40 75.25 78.40 82.00 89,20 99,92
B. D a t a for Tie Lines at 25' C. Over-all Composition Weight Yo n-Butylamine CeHsCl %Butylamine Ha0 CsHsCl layer HzO layer
49.00 46.03 43.35 26.40 16.35
6.50 12.22 17.30 18.45 18.98
Estimated plrtit point
10.7
CgHgCI
Figure 4.
22.0
44,50 41.75 39.35 55.15 64.67
7.16 15.00 21.00 24.48 26.85
5.15 7.86 9.58 11.46 14.22
67.3
H20
System: Chlorobenzene-Water-Pyridine 25' C. Isotherm
The data for the systems involving bases are of greater interest in view of the relatively greater selectivity of chlorobenzene for solutes of this type. The data show chlorobenzene to be selective for n-butylamine a t all concentrations, though its usefulness as a selective solvent for separating n-butylamine and water is limited by the fact that the range of immiscibility of chlorobenzene and water is greatly reduced by the solute. Complete miscibility of chlorobenzene and water at 25' C. is produced by concentrations of n-butylamine in excess of 28 weight %. At certain other temperatures this limitation on the range of applicability of chlorobenzene as a selective solvent might become less serious. This system is similar in this temperature range to the system water-diethylamine-toluene investigated by Wehn and Franke ( I S ) , though the -selectivity of chlorobenzene for nbutylamine is greater than that of toluene for diethylamine. The useful solubility range is, however, greater in the waterdiethylamine-toluene system. Data obtained during this investigation (not reported) for the n-propylamine-chlorobenzene-water system showed similar properties, but the range of complete miscibility extends to even lower concentrations of n-propylamine than for n-butylamine. The conclusion is evident that chlorobenzene is not entirely suitable as a selective solvent for the lower aliphatic primary amines a t 25' C. The system involving pyridine differs from the other three in that it exhibits the phenomenon of solutropy. This phenomenon involves a change in selectivity of the solvents for the particular solute species and is evident from the equilibrium diagram (Figure 4) as a change in sign of the slopes of the tie lines. The phenomenon was discussed by Smith (ZO), who cited eleven systems exhibiting this behavior. It was discussed further by Smith, Stibolt, and Day (11), who gave additional examples and showed the effect of variation of temperature on the solutrope in the system involving pyridine, benzene, and water. Thia latter system was apparently first studied by Woodman and Corbet (14). There is a strong similarity between this system and the pyridine-chlorobenzene-water system, as will be evident from comparison of Figure 4 with Figure 4 in the paper of Smith, Stibolt, and Day (11). As these authors have pointed out, the existence of a solutrope (horizontal tie line) does not prevent the separation of pyridine from water by benzene. The same applies for chlorobenzene. In this investigation no attempt was made t o study the effect of temperature on the solutropic behavior of the pyridine-chlorobenzene-water system. Further work of this kind would be helpful in determining how closely
TABLEIV.
SYSTEM:CHLOROBENZENE-WATER-PYRIDINE A.
Data for Solubility Curve a t 25' C. Chlorobenzene, Pyridine, Water, Chlorobenzene, Pyridine, Wt. % wt. % Wt. % Wt. % Wt. % 0.00 0.05 53.05 99.95 28.79
88.85 83.50 80.25 71.00 67.50 59,OO 54.75 52.00 48.20 43.00 39,60 95.30 32.35
10.50 0.65 25.45 22.80 15.600.90 20.60 18.58 1.17 27.20 1.80 19.05 30.00 2.50 15.42 36.50 4.50 12.45 39.40 8.40 5.85 41.20 6.80 5.75 43.58 8.22 2.85 46.40 10.60 2.60 48.02 12.38 1.19 50.16 14.54 0.40 51.60 16.05 0.08 ' B. D a t a for Tie Lines a t 25" C.
Over-all Composition CeHaCl Pyridine
48.00 44.15 41.00 38.25 34.70 31.40 27.15
8.55 15.68 21.85 27.15 33.90 40.30 48.35
Estimated plait point
37.8
49.0
HzO 43.45 40.17 37.15 34.60 31.40 28.30 24.50
54.20 54.95 55.60 55.80 55.68 55.00 52.70 48.40 40.75 39.40 31.31 22.60 0.00
Water,
wt.
%
18.06 20.35 22.25 23.80 25.15 28.90 32.55 38.90 45.85 56.40 58.00 67.50 77.00 99.92
Weight % Pyridine CeHsCl layer HzO layer
11.05 18.95 24.10 28.60 31.55 35.05 40.60
5.02 11.05 18.90 25.50 36.10 44.95 53.20
13.2
the two systems are parallel in behavior and the effect of the substitution of the chlorine atom for the hydrogen atom in the benzene molecule. LITERATURE CITED
(1) Doughty, H. W., and Black, A. P.,J. Am. Chem. Soc., 47, 1091
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127, 2461 (1925). RECEIWD for review January 7, 1952. .%CCEPTED April 28,1952. Contribution No. 541from the Department of Chemistry, Indiana University. Submitted by K. E. Thompson, Jr., in partial fulfillment of requirements for the degree of master of arzs.
