INDUSTRIAL AND ENGINEERING CHEMISTRY
618 TABLE Iv
APPARENT L\IOLECUL,AR FYEIGHTB SYSTEM I’,Oio-HsO
PlOio in
Apparent Mol. 1% t. of Vapor Experimental values Average 43.8,44.7,45.8,44.8 44.8 58.7, 5 0 . 0 , 5 9 . 2 56.0 108.7, 108.4, 1 1 1 . 8 109.6 1 3 2 . 0 ,123.5, 135.5, 132.2 137.0, 133.0, 130.2, 134.0
Liquid,
Wt. % 61. 5Q 72.46 88.0C 92.0d
a
OF
VAPOR
I N THE
~~~~~i~~ Calcd. Mol.vapo; Wt. is PaOn HzO 42.4 56.0 102.4 130.0
+
The apparent molecular weights derived from the vapor density measurements were compared with those calculated from assumptions that the vapor consisted of various binary combinations of H20, P4010,H3P04,Hapgo?,HPO,, (HPO&, and (HPO&. The striking agreement of the measured values with the values calculated on the basis of the P& and HpO combination (Table IV) leaves little doubt that the vapor over phosphoric acids of high P4010content at 1020” C. consists of a mixture of P,O,Oarid H 2 0 molecules.
HaPOa, 85%.
b HsP04. d
Vol. 44, No. 3
LITERATURE CITED
Approximate1.y (HPOdn doeotropic mvrture.
red heat. The lower value ~ o u l dmean that the vapor consisted of Ppoto and HzO molecules instead of H2P206 molecules. Data reported by Balareff (1) indicate that the meta acid dissociates upon vaporization. Balareff distilled metaphosphoric acid in a gold vessel and found that the vaporized product, as n-ell as the residue, contained less water than the theoretical content of 11.25%. He concluded that the rate of loss of water from metaphosphoric acid and the eventual composition of the acid are dependent upon the temperature and dyration of heating and upon the partial pressure of water vapor in the system. I n the present work, the density of the vapor over four acids (61.5, 72.4, 88.0, and 92.0% P401o)was determined by the Victor Meyer method in platinum apparatus. The measurements were made a t 1020’ C. to ensure rapid and complete volatilization of the acids, although i t was recognized that the molecular species found in the vapor a t this temperature would not necessarily be the same as would exist at lower temperatures.
Balareff, D., 2. anorg. u. allgem. Cham.,102, 34-40 (1917). Britzke, E. V., and Pestov, N. E., Trans. Sci. I n s t . Feitilizers (U.S.S.R.), NO. 59, 5-160 (1929). Elmore, K. L., Mason, C. M., and Christensen, J. €I., J . Am. Chem. Soc., 6 8 , 2528-32 (1946). Farr, T. D., “Phosphorus. Properties of the Element and Some of Its Compounds,” Tenn. Valley Authority, Chem. Eng. Rept. No. 8, 1950. Kablukov, I. A., and Zagvozdkin, K. I., Z. anorg. u. allgem. Chem.,224, 315-21 (1935).‘ Mack, Edward, Jr., and France, W. G., “A Laboratory Manual of Elementary Physical Chemistry,” 2nd ed., p. 77, New York, D. Van Xostrand Go., 1934. Robinson, R. A,, and Sinclair, D. A , , J . Am. Chem. Soc., 56, 1830-5 (1934). Tarbutton, G., and Deming, M. E., Ibid., 72, 2086 8 (1950). Tilden, W. A., and Barnett, R. E., Trans. Chem. Soc. (London), 69, 154-60 (1896). Zagvozdkin, K. I., Rabinovich, Yu. hI., and Batilko, N. A., J . A p p l i e d Chem. (U.S.S.R.), 13, 29-36 (1940). A c c r p r m October 17, 1951. RECEIVED for review J u l y 5, 1951. Presented a t the Southwide Chemical Conference, Wilmn D a m , Ala.. Octoher 1951.
LiquidHEPTADECANOL-WATER-ACETIC ACID AND HEPTADECANOLWATER-ETHANOL JAMES C . UPCHURCHI AND MATTHEW VAN WINKLE University of Texas, Austin, Tex.
S
UCCESSFUL development of liquid-liquid extraction systems and the design of the necessary equipment is extremely difficult without a knowledge of the phase equilibrium relations for the constituents involved. A knowledge of these data alloivs the prediction of the applicability of the process and permits a mathematical analysis of the extraction method used. The systems investigated in this study include the acetic aridheptadecanol-water system, at 25’ and 50’ C., and the ethanolhrptadecanol-water system a t 25“ C MATERIALS
The heptadecanol used in this investigation was obtained from Union Carbide and Carb?n Chemicals Corp. The glacial acetic acid was secured from Allied Chemical and Dye Corp. and was obtained as a 99.5% pure compound. The 100% ethanol wah obtained from U. S. Industrial Chemicals, Inc. All water used in this investigation was distilled, and the water used in the arid systems was also boiled to remove any carbon dioxide present. 1
Present addreas. Carbide and Carbon Chemicals Corp., Texas C i t y , Tex.
PROCEDURE
There are various experimental procedures for the determination of ternary equilibrium data. The methods of Othmer ( d ) , Taylor ( 5 ) , and Othmer el al. ( 4 ) are probably the most widely used. The latter method was used in this investigation since the techniques involved were considered more adaptable to the systems investigated. In this method the mutual solubility curve and the tie line data are dptermined separately in the analyses of ternary equilibrium, I n the determination of the solubility curve a known amount of solvent was measured into a flask from a calibrated buret. This made possible the calculation of the weight quantity present. The diluent was then added to the solvent in a dropwise manner, with constant agitation of the flask, until the solution became turbid. This indicated that the solvent phase was then saturated with diluent. The recorded volumes were then converted by means of the known weight per volume delivered calibrations to weight percentages. This particular point represented the solubility of the diluent in the solvent since no solute was present. To this turbid mixture a known amount of the solute was added, and because of its consolute effect a clear solution resulted. This addition
March 1952
INDUSTRIAL AND ENGINEERING CHEMISTRY
WEIGHT PER CENT WATER
Figure 1. Refractive Index at 30" C. of Saturated Phase at 25" C. for System EthanolWater-Heptadecanol 'OOn
WEIGHT PER GENT WATER
Figure 2. Liquid-Liquid Equilibrium of System Acetic Acid-Water-Heptadecanol at 25" C.
8A
Solubility data Tie line data Estimated plait point
619
moved the over-all composition to a point in the single phase region. Again the diluent was slowly added with constant agitation until the solution became turbid. As before, the resulting composition represented a point on the solubility curve; however, the solute concentration had been increased. This process was continued with successive points along the saturation curve being determined, each having a higher solute concentration, until the peak of the solubility curve was reached or until the coqtinued addition of solute would no longer produce a two-phase region. The second half of the mutual solubility curve was determined in the same manner as the first half. I n this case a known amount of diluent was measured into a flask and the solvent was added until the mixture became turbid. This was continued with successive additions of solute until the solubility curve was completed. I n the determination of tie line data for the acetic acid-heptadecanol-water system, known amounts of each component were measured into a 125-ml. Erlenmeyer flask. The flask was tightly stoppered and the solution was then shaken vigorously to ensure thorough contact between the phases. It was then placed in a constant temperature bath and allowed t o settle. The mixture was allowed to stand in the constant temperature bath for approximately 3 hours so that equilibrium could be attained. At the end of the 3-hour period samples were removed from each phase, weighed, and titrated to determine the acid composition of the saturated hases. The titration was conducted using a 0.2 N standard so?ution of sodium hydroxide with phenolphthalein as an indicator. By knowing the acetic acid concentration in the water-rich phase the equilibrium composition point can be established on the previously determined saturation curve. A line connecting this point and the total composition point establishes the tie line. The previously determined composition point ' in the heptadecanol-rich phase serves only as a check, as the results of this titration of the acid in this phase are less accurate than those obtained from titration of the acid in the water-rich phase. The tie line data for the ethanol-heptadecanol-water system were determined by the "synthetic" method as illustrated in Figure 1. In this method the mutual saturation curve was determined in the same manner as that of the acetic acid-heptadecanolwater system. After each experimental point on the curve was determined, a sample of the solution was removed and the refractive index was determined at a temperature 5" C. above the temperature a t which the system was run. These refractive indexes were determined with a Bausch and Lomb precision refractometer using monochromatic sodium d light. Having the saturation compositions and the corresponding refractive indexes, it was possible to construct the plot shown in Figure 1. In this figure the refractive index and the ethanol composition in the saturated phase were plotted as ordinates against the water composition in the saturated phase as the abscissa. The two resulting curves were used in conjunction with each other for the determination of the tie line data. To determine the tie lines, mixtures of a fixed total composition were prepared as before. After they had been allowed to reach equilibrium a t a constant temperature, samples of each phase were taken and the refractive indexes determined. By knowing the refractive index of each phase and by use of Figure 1, the equilibrium compositions were determined as illustrated. Since the points representing the compositions of the two phases in equilibrium and the over-all composition must all lie on the same straight line, a check on the experimental data was obtained, ACETIC ACID-HEPTADECANOL-WATER SYSTEM
WEIGHT PER CENT ACID H WATER PHASE
Figure 3. Distribution of Acetic Acid between Water and Heptadecanol at 25" C.
The acetic acid-heptadecanol-water system was investigated a t 25" and a t 50" C. The mutual solubility and distribution data were determined and are presented in Figures 2 through 5 and Tables I through IV. The estimated accuracy of the data is approximately 0.2% by weight. The effect of temperature on the acetic acid-heptadecanolwater system was slight. This is exemplified by the solventdiluent binary equilibrium and the maximum concentration of
Vol. 44, No. 3
INDUSTRIAL AND ENGINEERING CHEMISTRY
620
90 80 E!
2 70
E 6
60 50
@2
w 4 0 n I-
5 Y
30 20 IO
IO
'0
20
0
40 50 60 WEIGHT PER CENT WATER
30
Figure 4. Liquid-Liquid Equilibrium of System Acetic .4cid-Water-lIeptadecanol at 50' C. 0 Solubility data @ T i e l i n e data A
WEIGHT PER CENT ACID IN WATER PHASE
Figure 5. Distribution of Acetic Acid between Water and IIepttidecanol a t 30' C,
Estimated plait point
T.4BLE
solute in the two-phase region. The solubility of heptadecanol injrvater Rith no acid present was fourid to be less than O.lyoa t both 25" and 50" C. The solubility of rr-ater in heptadecanol with no acid present was less than 0 1% a t 25' C. while at 50" C. it was only 0.8%. This conerntiation is also a measure of the consolute effect of the solute. The tendency of the branches of the mutual solubility curve to rise closely to the 0% heptadecanol and 0% water sides of thc
T.4BLE
I.
EXPERIMENTAL hICTlJAL ~ O L U B I L I T Y DATA
System heptadecanol-acetic acid-water a t 25O C. Heptadecanol, ', Weight Z
99.9+ 96.7 93.5 88.2 78.9 74.8 71.5 65.4 59.9 53.6 49.9 41.4 37.2 32.9 29.6 28.9 26.7 24.2 22.2 21.5 20.9 19.5 18.2 17.0 16.1 15.2 14.4 13.8 13.1 8.1 7.3 5.3 5.3 5.2 3.2 2.9 2.6 2.3 2.0 1.7 1.4 1.3 1.1 0.9 0.8 0.6 0.4 0.2 0.3 0.2 0.1
ricetic Acid, Weight %
n
3.0 D.Y
11.0 19.8 23.6 26.8 32.7 37.8 43.6 47.2 54.8 58.5 62.2 65.1 65.6 67.6 69.6 71.3 71.9 72.4 73.6 74.6 75.6 76.3 77.0 77.6 78.1 78.6 81.9 82.2 82.9 82.7 82.7 82.5 82.2 81.8 81.4 80.9 80.3 79.: 78.I 77.7 76.6 75.3 73.8 72,l 70.1 67.5 64.6 0
11. EXPERIMESTAI, TIX-LINEDAT.1
System heptadecanol-acetic acid -water a t 2 5 O C, Total. Composition, Weight % - Heptadecanol
Acetic acid
Water
Acetic .Acid in Water-Rich Phase, W t . '%
.4cetic Acid in Heptadecanol-Rich Phase, W t . yo
2.4 4.8
Estimated plait point
73 6
73.6
P1rrtr.a SOLUBILITY DATA TABLE 111. EXPERIMENTAL
Water, Weight %
0.1 0.3 0.6 0 8 1.3
System heptadecanol-acetic acid -water a t 50° C. Fhptadecanol, Acetic Acid, Water. Weight % Weight % Weight %
?.! I. I 1.9 2.3 2.8 2.9 3.8 43 4.9 5.3 5.5 5.8 6.2 6.5 6.6 6.7 6.9 7.2 7.4 7.6 7.8 8.0 8.1 8.3 10.0 10.5 11.8 12.0 12.1 14.3 14.9 15.6 16.3 17.1 18.0 19.0 20.0 21.2 22.5 23.9 25.6 27.5 29.7 32.2 35.2 99.9f
0.8
99.2 9R.n 87.6 74.7 50.8 37.0 22.4 19.3 18.1 16.6
1.2 1.5 1.9 2.8 5.1 7.5 8.3 8.4 8,D 9.3 9.7 10.2 10.8 11.7
15.1
13.6 12.3 10.5 8.5 5.4
14.0 14.3 15.5 17.3 18.9 22.5 27.6 29,7 32 2 35.2 43.2 99 Q +
5 0
4.0 3. 0 1.8 1.0 0 5 0.3 0.3 0.2 0.1 '
0.1
TABLEIv.
EXPERIMENTAL
TIE-LINEDATA
System heptadecanol-acetic acid-water a t 50' C
__ Total Composition, Weight % Heptadecanol
Acetic acid
Estimated plait point
Water
Acetic Acid in Water-Rich Phase, W t . 70
64.0
Aoetic Acid In, EIeptadecanol-Rich Phase, Wt. 7'0
64.0
100
621
INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1952
n
100 07 W
2
90
d
80
3 70 t
Y@J z
$
50
;40 k
30
V
20
c
$
IO
L '0 WEIGHT PER CENT WATER
Figure 6. Liquid-Liquid Equilibrium of System Ethanol-Water-Heptadecanol at 25" c.
0
Solubility data @ Tie iine-data A Estimated plait point
diagram (with increase in acetic acid concentration) is an indication that a minimum amount of water is dissolved in the heptadecanol phase and a minimum amount of heptadecanol is dissolved in the water phase. This is highly desirable for the transfer of solute from the diluent to the solvent phase. The distribution data for the acetic acid-heptadecanol-water system were determined at 25" and 50" C. and are presented in Tables I1 and IV and in Figures 3 and 5. There was no appreciable change in the distribution of acetic acid between the heptadecanol and water phases with change in temperature. The
MUTUAL SOLUBILITY D.4TA TABLE v. EXPERIMENTAL System heptadecanol-ethanol-water at 25O C. Heptadeoanol Ethanol, Water, Refractive Index Weight % Weight % Weight % at 30- C. 01 1.4483 0 99.9s 1.4390 8.5 15 90.0 1.4336 13.5 I8 84.7 25 18.5 1 ,4288 79.0 42 1.4179 28.5 67.3 1.4081 37.0 6 7 56.3 9 4 1.3995 43.9 46.7 1.3895 13 1 52.2 34.7 1.3812 17 1 58.1 24.8 1.3731 21 4 63.6 15.0 1.3685 65.8 24 9 9.3 1.3668 65.7 26 8 7.5 1.3667 27 1 65.7 7.2 1.3632 32 7 63.8 3.5 43 5 55.7 1.8 1 :3555 41.1 58 7 0.2 68 5 31.3 0.2 21.1 1 :3459 78 8 0.1 0 1.3320 99 9f 0.1
TABLEVI.
EXPERIMENTAL
TIE-LINE DATA
System heptadecanol-etbanol-water at 2 5 O C. Total Composition, Heptadecanol-Rich Phase Weight % Water-Rich Phase Refractive Ethanol, Refractive Ethanol, Heptadeoanol Ethanol ' Water index, 30' C. wt. % index, 30' C. wt. % 1.3369 49.9 1.4461 7.4 45.0 5.1 2.0 1.4415 21.7 1 .3462 15.0 6.4 44.9 40.1 1,4367 1.3524 34.7 24.7 10.8 40.6 33.8 1.4311 1.3570 30.0 35.0 16.4 35.0 45.8 45.0 1,4251 56.1 1,3600 24.9 21.4 30.1 55.0 29.8 25.0 1.4163 63.9 1.3634 20.0 35.4 22.0 1.4104 65.7 1.3663 58.0 20.0 1,4042 65.3 1.3701 40.6 19.0 23.0 58.0 20.0 1.4024 65.0 1.3705 41.8 20.0 60.0 1.3711 42 2 1,4030 54.0 16.0 64.8 30.0 50.2 15.1 1.3947 60.8 1.3775 54.9 30.0 Estimated plait point 56.8 56.8
IO
20 30 40 5 0 60 7 0 80 90 WEIGHT PER CENT ETHANOL IN WATER PHASE
100
Figure 7. Distribution of Ethanol between Water and Heptadecanol at 25" C.
acetic acid showed a much greater affinity for the water phase than for the heptadecanol phase. The plait points which are labeled on the curves represent the intersection of the diluent and solvent branches of the solubility curve. In each case they are determined by the extrapolation of the distribution curves. This is the point where both phases have the same composition and density. ETHANOLHEPTADECANOL-WATER SYSTEM
The mutual solubility and distribution data were determined for the system ethanol-heptadecanol-waterat 25' C. These data are presented in Tables V and VI and in Figures 6 and 7 . The consolute effect of the ethanol was somewhat greater than that of the acetic acid. This is exemplified by the increase in solubility of the heptadecanol and water with increase in solute concentration. From the distribution curve in Figure 7 it may be seen that the ethanol has a greater affinity for the water phase than for the heptadecanol phase. The ethanol showed a more even distribution between the two phases than did the acetic acid. The estimated accuracy of these data is approximately 0.1% by weight. CORRELATION O F DATA
The data presented here were examined mathematically by the methods outlined by Bachman (1)and by Othmer and Tobias (3). Both methods enabled correlation of the data reasonably well except in the region of the plait points. The acetic acidcontaining systems correlated better than the ethanol-containing system throughout the range of data. ACKNOWLEDGMENT
It is the wish of the authors to express their appreciation to the Union Carbide and Carbon Corp. for their donation of the heptadecanol used in this investigation. LITERATURE CITED
(1) Bachman, U., IND. ENG.CHEM.,ANAL.ED.,12,38 (1940). (2) Othmer, M. E., Chem.& Met. Eng., 43,325 (1936). (3) Othmer, D. F., and Tobias, P. E., IND.ENG.CHEM.,34, 693 (1942). (4) Othmer, D. F., White, R. E., and Trueger, E., Ibid., 33, 1240 (1941).
(5) Taylor, H.S., "Treatise on Physical Chemistry," Vol. 11, 2nd ed., pp. 570-82,New York, D.Van Nostrand Co., 1931. RECEIVED for review June 25, 1951. ACCEPTED October 8, 1951. Abstracted from a thesis presented in partial fulfillment of the requirements for the M.S.Ch.E. degree, University of Texas.
