Boiling Binary Solutions

(21) Starr, Tilton, and Hociiberger, IXD. ENG. CHEX. 39, 195 (1947). (22) Streiff and Rossini, J. Reseccrch Satl. Bur. Standarda, 39, 303. (23) Thomas...
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INDUSTRIAL AND ENGINEERING CHEMISTRY

(12) Griswold a n d Walkey, Ibid., 41, 621 (1949). (13) Jones, Friedel, a n d Hinds, IXD.ENG.CHEM.,ANAL.E D . , 17, 349 (1945). (14) Kilpatrick, Prosen, Pitaer, and Rossini, J . Research 'Vatl. Bar. Standards, 36, 559 (1946). (15) Marschner a n d Cropper, IND.ENG. CHEM.,38, 262 (1946); 41, 1357 (1949). (16) Marschner a n d Cropper. Proc. Am. Petroleum Inst., 26, 111, 41 (1946). (17) Melpolder, Brown, l o u n g , a n d Headington, IKD. EXG. C H E h i . , Ibid., 44, 1142 (1952). (18) R a m p t o n , J . Inst. P e t r o h m , 35, 42 (1949). (19) Rossini, Chem. Eng. S e w s , 25, 230 (1947). (20) Rossini, Prosen, and Pitzei, J . Research S a t l . Bur. Standards, 27, 529 (1941).

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(21) Starr, Tilton, and Hociiberger, IXD. E N G .CHEX.39, 195 (1947). (22) Streiff and Rossini, J . Reseccrch S a t l . Bur. Standarda, 39, 303 (1947). (23) Thomas, IXD.EKG.CHEM.,41, 2564 (1949). (24) Thomas and coworkers, J . Am. Chenz. Soc., 61, 3571 (1939); 66, 1586, 1589, 1694 (1944). (25) Voge, Good, a n d Greensfelder, IND.ENG.CHEAI.,38, 1033 (1946). (26) Wilson, Proc. Am. P e f r o l e r ~ n Inst., ~ 30, 111, 16 (1950).

RECEIVED for review M a y 7 , 1961. ACCEPTED January 14, 1952. Presented as part of the Symposium o n Composition of Petroleum and Its Hydrocarbon Derivatives before the Division of Petroleum Chemistry a t C H E h r I c A L SOCIETY, Cleveland, Ohio, the 119th Meeting of the AMERICAN h p r i l 1951.

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Boiling Binary Solutions Pressure Equilibrium Still for Studying Water-Acetic Acid

System DOK-4LD F. OTHMER, SAL J. SILVIS', AND ALBERT SPIEL? Polytechnic Znstitute, Brooklyn 2 , N . Y .

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HE phase relations (temperat'ure t, pressure p , liquid coniposition 2, and vapor composition y ) and other t,hermodynamic properties of systems containing acetic acid, particularljthe one with water, have been determined frequently, not only because of the industrial importance of this most used organic acid but also because of the inapplicability of the general equations and correlations derived for ot,her liquids and liquid solutions. Since these relations require a knowledge of the molecular weight of t.he material under consideration, the deviation of acetic acid and its solutions from normal behavior has been attributed to the association of the acetic acid molecules, both in the liquid and the vapor phases ( 4 , 7 , 10, 11, 15, 26). As the most, important industrial organic acid, it exemplifies some properties in aqueous solutions which may account for some of the abnormalities encount,ered. Furthermore, it is the only volatile acid for which a constant boiling mixture with water has not been reported. The water-acetic acid system has now been st,udied, and p , t, x, and y measurements have been made a t constant pressures ranging from 0.387 to 315 pounds per square inch absolute. This has been extended to 515 pounds per square inch absolute for that part' of the system containing largely water, and within the range below 515 pounds per square inch absolute no azeotropic mixture was found. The unit for obtaining the experimental data was especially designed and built for these studies; it is a modification of those described in previous articles (8, 13, 16-19, 2 2 ) wherein the temperatures and pressures are measured directly, n.hile the liquid and vapor compositions in equilibrium are determined by suit,able analysis of samples withdrawn from the still body and condensate traps, respectively. Rat,her than having an external pressure reservoir filled with a noncondensable gas (as), the system was operated with the condenser connected directly to the pressure measuring and regulating system. This made it necessary to balance more precisely the heat supplied to the still and removed from the condenser, which \vas not difficult and gave some Present address, Colgate-Palmolive-Peet Co., Jersey City. X. J. Present address, Kational Dairies Research Laboratories, Oakdale, Long Island, N. T. 1

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advantages of a theoretical and piactical nature TO the operational technique. Methods developed by Othmer and Gilmont (20) were used to correlate the dat,a. APPARATUS

The unit used for determining the liquid-vapor equilibria W H Z constructed and tested a t a pressure of 1000 pounds per square inch absolute by the Vulcan Copper and Supply Co. of Cincinnati, Ohio, entirely of Type 316 stainless steel component,s welded t,ogether. It is shon-n to scale in Figure 1. This type of stainless &el is knon-n from wide indust,rial use to be the most resistant of practical mat,erials of construction to the corrosive act,ion of boiling acetic acid and water-acetic acid solutions at, atmospheric pressures, and it was expect'ed to be more rei;istant than an!other a t higher pressures. EauILIBRIuhr USIT. The still body consisted of a 4-inch standard pipe size ( W S ) Type 316 stainless steel (SS)tube, 19 inches long. The bottom was formed of a 3/d-inch t,hick plate with three chambers extending up into the still body into which were inserted electrical heating cartridges. The 'ra-inch standard pipe size liquid sample draw-off line a.lso was welded t o this bottom plate. The body contained a thermocouple ~vell,T-1, for measuring the temperature of the boiling liquid and tvio peep sights, C, 90 apart for observing the boiling liquid. The top of the still body was formed of a 13j16-inchplate, with the inner face in the shape of a cone, I>, t o permit drainage of any condensate into the vapor outlet, E. To this top plate vas welded a thermocouple well, T-2, for measuring the vapor temperature, and an outlet line, F , for venting noncondensable gases. The vapor outlet line sloped 20 O doivnward from the horizont,al into the reflux-type condenser. This condenser was constructed of 4-inch standard pipe size, 10 inches long, with the upper 8 inches jacketed by a 6-inch standard pipe size section for the coolant. The top of the condenser contained two outlets of 1/8-inch standard pipe size with valves H and H' for venting and for a connection to the pressure measuring system, respectively. Below the condenser wa6 a drop-counter

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Figure 1. High Pressure Equilibriirm Still

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Still body, 4 X 19 inches long A . Chambers for cartridge heaters B . Liquid sample outlet with needle valve C. Peep sights, 90' apart and 1-inch differencein levels D . Cone-shaped top plate for allowing condensate to drain into vapor neck E . Vapor outlet pipe F . Vent valve for expelling noncondensable gases 6. Inlet tube for return of condensate, blanked at end with four l/s-inch holes to distribute liquid Condenser, 4 X 10 inch long inner tube with 6 X 8 ineh long shell H . Valve to pressure measuring system H'. Vent valve on condenser for expelling noncondensable gabes J . Condensate drop counter K . Peep sights on drop counter L . Valve to shut off condensate receiver from Condenser M . Valve to shut off condensate receiver from still body Interchangeable receivers, 1/a, ' 1 4 , and a/, inch, all 17 inches long N. Condensate sampling needle valve Loading chamber, 3 X 17 inches long P. Valve for venting noncondensables and evacuating loading chamber Q. Valve for charging still body from loading chamber R . Valve through which loading is accomplished and liquid sample is withdrawn Thermocouples T - I . Thermocouple for measuring temperature of boiling liquid T-2. Thermocouple for measuring temperature of equilibrium vapors T-3, T - 4 , T-5. Thermocouples soldered onto outside of still body t o measure temperatures at indicated places

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box, J , with peep sights, IC, for observing the rate of condensation and boiling during operation. A 1/8-inch standard pipe size line with a needle valve, L, connected the drop-counter box t o the condensate receiver. These were three flanged receivers of variable internal diameter and volume, provided with the unit which permitted vapor condensate samples of approximately 10, 20, and 30 ml. The choice of receiver depended upon the size of sample required for the analytical method used. Below the receiver the arrangement of l/S-inch standard pipe size piping and the two needle valves, M and N , directed the flow of condensate either back into the bottom of the still body during the attainment of equilibrium or t o the sample receivers after equilibrium had been established. Heat losses from the still body were eliminated by insulating and wrapping Nichrome wire around the outside. By carefully controlling the supply of external heat to the Nichrome windings, the temperatures a t 2'-3, T-4, and 7 ' 4 were maintained a t values equal to those within the still body, where T-1measured temperature of the boiling liquid and 7'-2 that of the equilibrium vapors. The condenser was also insulated and Nichrome-wired in a similar manner to prevent excessive heat losses a t the higher pressures. Air, tap water, or refrigerated water were used as cooling fluids in the condenser, depending on the temperature of the vapors in the various determinations. These temperatures varied from 70" to 470" F.

LOADING CHAMBER.T o eliminate the necessity of cooling the still and its contents and reducing the pressure t o atmospheric in order t o add liquid for changing the liquid composition, a loading chamber allowed such changes to be made while the system \$as at the operating pressures. This was constructed of a 17-inch length of 3-inch standard pipe size fitted t o the top and bottom with l/s-inch standard pipe size and appropriate valves, as shown. When it was desired to change the liquid composition, the loading chamber was first evacuated through valve P, while valves B , F , and R were closed and valve Q opened. P was then closed and a beaker of the liquid t o be charged was placed under the nipple leading to R, which was then opened to allow most of the liquid to be sucked into the chamber. R was then closed t o prevent air from being drawn into the chamber. A second evacuation allowed a small amount of liquid t o flash, and its vapors entirely purged any residual air. Valve F was opened slowly, equalizing the pressures within the still and the loading chamber; then valve B was opened t o allow liquid to flow into the still. When the charge was completed, B and F were closed, thus disconnecting the loading chamber from the still. As an added precaution, the still was vented to purge any air that might have entered during loading. The liquid remaining in the loading chamber was withdrawn through a condenser attached to R to ascertain that the charging operation was successful. SAMPLING BOMBS. At the superatmospheric pressures, bombs constructed of S/4-inchstandard pipe size, 7 inches long with both ends tapered and welded to '/s-inch standard pipe size nipples and l/S-inch valves, were used t o obtain samples of the liquid and the vapor condensate. These bombs were completely evacuated before being used. TiVhen samples here t o be taken, one valve of the bomb was screwed directly onto the nipple leading from either the valve from the still, R , or the valve from the distillate receiver, iV. The valve of the equilibrium unit and the valve of the bomb were opened to allow the sample to run into the evacuated chamber. The sample bombs were placed in ice-water trays and rapidly cooled. TENPERATURE MEASURINGSYSTEM. Temperatures were measured by means of iron-constantan thermocouples and a Leeds-Northrup potentiometer calibrated to read directly in degrees Fahrenheit. The potentiometer was previously checked against a standard potentiometer and calibrated cell. The ironconstantan thermocouples were checked by placing them in freshly distilled water and recording the boiling points of water a t various pressures. A mercury manometer capable of being read t o 0.1 mm. of mercury was used. Temperatures recorded checked those of ( 1 4 ) to within 0.2'%. The location of the thermocouples has been discussed previously and is shown on Figure 1.

PRESSURE MEASURIXG AND CONTROL SYSTEM. Pressures were measured with a n absolute mercury manometer for the subatmospheric studies and with a combination of a differential mercury manometer connected in series with a dead-weight gage for the superatmospheric studies, as shown in Figure 2. A '/s-inch

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Vol. 44, No. 8 A combination of manual control of heat input to the equilibrium unit and manual control of air or water coolant flowing through the condenser was used to control and maintain the desired superatmospheric pressures. A Gilmont manostat (6) was used to control the desired subatmospheric pressures.

E ANALYSES

The samples of liquid and vapor condensate were analyzed by titration for acid values. h DIFFERENTIAL part of the chilled liquid from MANOMETER a bomb was drained to previDEAD- WEIGHT ously weighed flasks, each conGAGE taining 25 ml. of 0.1 S barium hydroxide solution with two drops of phenolphthalein solution, until the pink color just EQUILIBRIUM U disappeared. These were immediately stoppered and STILL weighed. The arrangement of the back titration was such that Figure 2. -4rrangement of Equipment for Superatmospheric Pressure Investigations any contact of the basic soluInset shows equipment arrangement for subatmospheric investigations tion with carbon dioxide of the air was prevented. T h e standard pipe size line connected the top of the condenser of the barium hydroxide solutions were standardized against certified equilibrium still directly t o one side of the differential manometer. potassium acid phthalate obtained from the Kational Bureau of Standards. From the titers, the liquid and vapor compositions This line was completely filled with fluid, carbon disulfide being were obtained; these values were recorded along n-ith the templaced above the mercury in the manometer and i n the pipeline perature and pressure. up to the point W (see Figure 2) and a diIute aqueous solution of Titration showed the reagent grade acetic acid used in this acetic acid from point W t o the condenser. T h e solubility of investigation t o contain 99.8% acid by weight; the bulk of the carbon disulfide in this solution is negligible, so t h a t with this remaining constituents was assumed to be water, as the total arrangement no acetic acid came in contact with the mercury or amount of other constituents according to analysis was less than the manometer. The dead-weight gage was directly connected t o the down0.01% by weight. The water used \o within 0.1% by Temp., Temp., Temp Temp Temp., Temp., Temp., Temp., XU oc. OF. y b OC." OF." Y ' C . O F . Y O C . OF. Y weight. 0 30.0 86.0 0 54.9 0 79.9 175.9 130.9 0 118.2 254.3 0 A t the neutral point a 10 25.4 77.8 ~. 13.5 48.8 119.8 1 4 . 3 71.9 161.5 15.1 108.2 226.7 16.3 75.6 25.0 47.2 26.5 20 24.2 117.0 157.8 28.4 69.9 105.3 221.6 279 8 r e d d i s h - b r o wn amorphous 74.9 36.0 46.4 30 23.8 115.5 38.2 68.7 l 5 5 , 7 40.4 218.9 103.8 42 0 40 23.4 74.2 46.4 45.7 114.2 49.3 67.9 154.2 51.4 102.8 217.1 mass, the ferric basic a,cetate, 53 0 50 23.1 73.6 56.6 45.4 59.3 113.7 67.3 153.2 6 0 . 7 101.9 215.5 62 1 Fe(OH)(CH&OOH)?, precipi73.0 60 22.8 66.7 45.1 68.4 113.2 66.9 152.5 69.2 214.4 101.3 70 0 76.4 44.9 77.3 72.6 70 22.6 112.8 152.1 66,7 77.5 213.6 100 9 77.4 tated out. Enough alkali 85.3 72.2 80 22.3 44.7 112.5 85.8 151.7 85 6 66.5 213.0 100.5 85.2 90 22.2 94.0 44.6 72.0 93.7 112.2 66.4 151.6 100 2 9 3 . 2 212.4 92.6 was added t o maintain the 71.8 100 100 22.1 112.0 100 151.5 100 44.4 66.4 100 0 212.0 100 faint pink color. The precipi39.7 Lb./Sq. In. .4bs. 114.7 Lb./Sq. In. Abs. 314.7 Lb./Sq. In. Abs. tate was collected in a Gooch (2053 Mrn. Hg.) (5931 Mm.Hg.1 (16,270 Mm. HE.) Temp., Temp., Tzmp., Temp., Temp., Temp., crucible, dried, and weighed. x C. O F . u C. F. y C. F. y The iron in the precipitate 0 308.5 0 0 393.3 494.6 0 10 17.2 287.7 18.1 364.4 453.3 was calculated to be 2 % of 18.8 31.7 278.1 20 353.8 31.6 441.2 31.5 the weight, of Polution. This 44.3 273.7 30 44.1 348.4 434.8 42.7 54.4 271.4 40 53.5 344.6 430.5 52.3 was converted into a rat,e of 62.6 269.7 50 62.2 342.1 427.5 61.4 60 70 4 268.5 70.0 340.4 425.5 69.7 corrosion of the metal of ap77.5 267.6 70 77.5 339.3 423.9 77.0 84.6 267.1 80 338.5 84.2 422.9 83.9 proximately 0.67 inch of pene266.9 92.3 338.1 91.7 90 422.2 91.3 tration per year. 266.8 100 100 421.7 100 337.9 100 To determine if the product,s a x = liquid. b g = vapor. of cwrrosion affected cquilih-

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line decreases, so that it appears unlikely that a n azeotrope would be formed within the pressure limits of 50 % the equipment used. 60While it has been shown that the 40 % n 50 plot on logarithmic paper of the vapor 40compositions against either the vapor a > -= pressures of a reference substance or Z 30the total pressures should give straight 20 % a lines for either ideal or nonideal sys+ s tems (20), the lines of Figure S are slightly bowed over the range (approximately 1000-fold) of the pressure range investigated. This is in itself not a bad demonstration of the usefulness of this method of correlation, but it is I I I I I I I I I I I I I I I l l / I / I 20 40 6 0 8 0 IO 20 40 60 EO 100 200 300 believed that the reason for even this TOTAL PRESSURE PSlA deviation is due to the fact that varg ing amounts of three components (water Figure 8. Logarithmic Plot of Vapor Composition versus Total Pressure at and monomer and dimer of acetic acid) Constant Liquid Compositions are present and being considered as only two in the variation in the amount are also expressed in centigrade degrees and millimeters of of association of the acetic acid molecules over this temperature mercury pressure. range. Thus, there is not involved the vapor composition of t1v.o These data were correlated by the methods of Othmer and molecular species, but of three or more, to give corresponding Gilmont (SO),wherein straight lines are obtained when: deviations from lines derived for materials of constant qtructure. 1. The logarithms of the total vapor pressure, the partial COMPARISON WITH OTHER DATA vapor pressures, the vapor compositions, the equilibrium constants, activity coefficients, or relative volatilities of a solution of Since there have been no data published on the acetic acid-water constant concentration are plotted against the logarithms of the system in the superatmospheric range, the only compai :son that vapor pressure of a reference substance (usually water) at the can be made with the data of this investigation is in the atmossame temperature, or pheric and subatmospheric region. Data a t subatmospheric 2. The logarithm of the vapor composition in equilibrium pressures were compared with those of Gilmont and Othmer ( 8 ) , with a liquid of constant composition, the equilibrium constants, and Kahlbaum and Konowalow (12). A plot of the logarithm the activity coefficients, or relative volatilities are plotted against of the total pressure of the system versus the logarithm of the the logarithm of the total vapor pressure of the system. All of these are not included in the figures, but some are shown TEMPERATUREin Figures 7, 8, and 9. Figure 9 is calculated on the basis of 0 always assuming Dalton's law and on the existence of acetic acid as a monomer. Both of these are known to be in error under existing conditions, but, nevertheless, the correlation indicated by the straightness of these lines is excellent. The effect on the boiling point diagrams (Figures 3 and 4)of increasing pressure is to increase the difference in the boiling points of acetic acid and water. This was to be expected since the vapor pressure plot of the pure components in Figure 8 shows their vapor pressure lines t o diverge as the pressure is increased. Although this would generally indicate an increasing relative volatility of the lower boiling component, this was only true in the low water concentrations. The reverse occurred at the high water concentrations with the vapor compositions in equilibrium with a liquid actually decreasing in water with increasing pressure. Thus, the 2, y curves of Figures 5 and 6 have reversed themselves, the equilibrium line of 0.387 pound per square inch absolute being the closest to the 45 O line in the low water concentrations and the furthest away in the high water range. Similarly, the equilibrium line of 314.7 pounds per square inch absolute bows furthest away from the 45" line at the low water concentrations and dips closest towards the 45' line of pure water a t the high water concentrations. This tendency of the equilibrium line to dip towards the 45" line with increasing pressure indicated the possibility of the formation of an azeotrope if the pressure were raised still higher than 314.7 pounds per square inch absolute. Vapor-liquid equilibrium VAPOR P R E S S U R E OF WATER ' , ' S t i .n 10 100 determinations were made a t a pressure of 515 pounds per square 0.I 1l111il I I Illllll I I I111111 I 1 IllllJ inch absolute in the 94 t o 100% water range. As will be noted from the plot of the data obtained, Figure 10, the equilibrium Figure 9. Logarithmic Plot of Partial Pressure of Acetic curve comes closer t o the 45 line, but there is no formation of an Acid versus Vapor Pressure of Water at Constant Liquid azeotrope. Also, the rate a t which the curve approaches the 45' Compositions -

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INDUSTRIAL AND ENGINEERING CHEMISTRY

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Figure 10. Vapor-Liquid Equilibrium in the High Water Region A t 515 pounds per square inch absolute c

v a p o r p r e s s u r e of water showed these data to be in good agreement. F i g u r e 11 shows the vaporliquid e q u i l i b r i u m data a t atmospheric pressure reported by various investigators (1-3, 6,8,17, 63-26, 27, 88) as compared with those obtained in this investigation. Wherever p o s s i b l e , the original observations of the investi-* gators were chosen rather than the

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smoothed data. The atmospheric data of Cornell and Montanna ( 3 ) agree to within 0.1 weight % ’ with those obtained here, and these investigators also took the precaution to prevent any possible heat losses (with subsequent condensation and fractionation) from the equilibrium unit. Because the apparatus of Othmer and Gilmont (8) did not have insulation and heating, it is felt that the data presented here are to be preferred, although the differences are not major. For atmospheric or subatmospheric work, the glass still is, of course, equally good if insulated and heated as described by Othmer and Karr ( 1 3 ) . ACKNOWLEDGMENT

Appreciation is gratefully expressed to the Vulcan Copper and Supply Co. for assisting in the design and for fabricating the equilibrium unit and the attendant equipment, and t o the Emil Greiner Co. for the Cartesian diver-type manostat and the high pressure differential manometer. Thanks are especially due Roger Gilmont for his numerous suggestions.

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Figure 11. Comparison Plot of Data Obtained in Present Work with Those Reported in Literature

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INDUSTRIAL AND ENGINEERING CHEMISTRY LITERATURE CITED

(1) Bergstrom, as quoted by Hausbrand, E., ”Principles and Practice of Industrial Distillation,” 4th ed., p. 238, New I-ork, C h a p m a n a n d Hall, 1925. (2) Blacher, a s quoted by Hausbrarid, E., I h i d . , p. 238-42. aiid M o n t a n n a , R. E., IND.E N G . CHEii., 25, (3) Cornell, L. W., 1331 (1933). (4) Fenton, T. M., and Garner, W. E., J . Chem. SOC.,1930, 694. (5) Garwin, L., and Hutchison, K . E., IND.ENS. C H E M . ,42, 727 (1950). (6) Gilmont. R., IND. ENG.CHEM.,ANAL.E D . , 18, 633 (1946). (7) Gilmont, R . , P h . D . thesis, Polytechnic Institute of Brooklyn, J u n e 1947. (8) Gilmont, R., a n d Othmer, D. F., IND.EBG. CHEM.,3 6 , 1061 (1944). (9) Gilmont, R., Weinman, E. A, K r a m e r , F., Miller, E., Hashmall, F., a n d Othmer, D . F., I b i d . . 42, 120 (1950). (10) H e r m a n , R. C., aiid Hofstadter, R., J . Chem. Phys., 6 , 534 (1938). (11) .Johnson, E. IT.,arid Nash, L. K . , J . Am. Chem. SOC.,72, 547 (1950). (12) Kahlbaum and Konowalow, “International Critical Tables.” Vol. 111, p , 306, S e w Tork, McGraw-Hill Book Co., 1928.

Vol. 44, No. 8

(13) R a r r , A. E.. Scheibel. E. G.. Rowes. W. 31,. a n d O t h m e r . D. 12.. IND.E m . CHEW,43, 961 (1951). (14) Keenan, J, M.. a n d Keyes, F. G.. “Thermodynamic Propertlcs of S t e a m , ” New Tork, J o h n Wiley 8: Sons, 1936. (15) MacDougall, F. H., J . Am. Chem. Soc., 58, 2585 (1936). (16) Othmer, D . F., Anal. Cheiia., 20, 763 (1948). ENG.C H E l x . , 20, 743 (1928). (17) Othmer, D . F., IND. (18) Ibid., 35, 614 (1943). E X G . CHEM.,ANAL.ED.,4, 232 (1932). (19) Othmer, D. F., IND. (20) Obhmer, D. F., a n d Gilmont, R., 1x0. ENG.CHEM.,36, 858 f 1944). (21) Ibid., 40, 2118 (1948). (22) Othmer, D. F., a n d Moiiey, F. R.. Ihid., 38, 751 (1946). (23) Pascal, P., D u p u y . E , a n d Gainier, Bull. SOC. chim. France 29, 9 (1921). (24) Povarnin, G., a n d Markoi-. V., J . Russ. Phys. Chein. Sac., 55, 381 (1924). (25) Rayleigh, Phil. MuO., 4, Yo. 6, 521 (1902). (26) Ritter, H . L., a n d Simons, J. H., J . Am. C h e m Soc., 6 7 , 757 (1945). (27) Sorel, E., C o m p t . r e n d . , 122, 046 (1896). (28) York, R., Jr., a n d Holmes, R. C . , IND.ENS. CHEar., 34, 346 (1942). R X E I V E Dfor review March 1, 19.51,

ACCEPTED February 2 1 , 19.52.

(COMPOSITIOS OF VAPORS FROM BOILI-NG BINARY SOLL-TIOll;S)

Binary and Ternary Systems of Acetone, Methyl Ethyl Ketone, and Water DOSALD F. QTHMER, MANU M.CHUDGAR, AND SHERSI.4N L. LEVY Polytechnic I n s t i t u t e of Brooklyn, Brooklyn,

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Tu’ T H E commercial synthesis of methyl ethyl ketone, acetone

is produced as a concomitant product; water is also present. Vapor-liquid equilibrium data are necessary for the separation of this mixture by fractional distillation as a step toward manufacturing high purity ketones. Furthermore such data were desired because of the interesting thermodynamic properties of this system. APPARATUS AND OPERATIhG PROCEDURE

An equilibrium still of the recirculating type which has been developed during the past 20 years for studying phase relations was fabricated from Type 316 stainless steel to permit studies t o be made a t pressures up t o 500 pounds per square inch absolute. The design and operation of this equipment have been described in a previous paper (17‘). The operating procedure was similar to that for the standard glass equilibrium still ( l a ) and has been discussed (f7). Particular reference has been made (6) to the supplying of external heat t o eliminate radiation losses; this is particularly necessary under the high temperatures encountered here. Pressure was measured with a combination of a dead-weight tester in series with a differential mercury manometer, and LYas controlled by balancing the heat input and output ( 1 7 ) . Temperatures a t the v a r i o u s points of the system were measured with 20 B. &. S. gage ironconstantan thermocouoles which were accurate within h 0 . 3 ‘ C. Previous investigators ( 17‘) have used sample bombs to collect for analysis samples of the two phases in equilibrium. For the systems methyl ethyl ketone-water and acetone-methyl ethyl ketone-water, there is a range of compositions where either the or both is miscible at the equi]ibliquid or the vapor rium temperature but immiscible a t room temperature. I n this range, an error would be introduced by using sample bombs because of the separation of the mixture into two phases upon cooling and subsequent disproportionate adherence of droplets on the n.alls while emptying the bombs. To circumvent this difficulty, small coolers nere used to allow the sample to be taken directlv in

N. 1..

the glass vessel used for aiialysis. They were made of xat,erjacketed copper tubing, having an inside diameter of 4 mm., and Tyere connected directly to the out,lets for sampling boiling liquid and condensate. These were cooled with ice water. About 25 1111. of cold samples were collected for analysis in test tubes immersed in a mixture of ice and water. This met,hod of sampling was checked in the miscible region of the methyl et,hyl ketonewater system a t 100 pounds per square inch absolute by redetermining the vapor liquid equilibrium curve obtained with the use of sample bombs. An excellent check was obtained. PERFORMANCE OF THE EQUILIBRIUM STILL

Tests were run for possrblc entrainment a t each of the fivc pressures studied. The still was charged with a highly colored solution of methyl orange of a known concentration. The vapor condensate sample was collected as in an actual run and examined in a spectrophotometer. From a calibration curve of standard samples, the concentration of methyl orange in the distillate n-as determined. It was found t h a t the entrainmcnt was only 0.014% of the condensate, which is insignificant. The experimental data for the system methyl ethyl ketonewater a t atmospheric pressure n ere compared with those of the literature (13, 2 3 ) in Figure 10. The agreement is within the limits of analytical accuracy. MATERIALS USED

Commercial grade synthetic acetone was dried with anhydrous calcium chloride t o remove water or lower alcohols and distilled in a batch-rectifying column. .4 middle portion comprising 80% of the total mas collected a t a constant boiling temperature. hiethyl ketone was purified. The distilled as required, and the refractive index and density of each batch were checked before use. Distilled x-ater from the laboratory &’asused without further purification. The atmoepheric boiling points, refractive indices, and densities for t h r ketone used in this wOr]i arc givPn acetoneand Table I.