556
INDUSTRIAL AND ENGINEERING CHEMISTRY
The viscometer cup was filled with the same volume of sample for each series of determinations. The time required for 100 revolutions of the paddle was determined nit11 a stop watch. From the time in seconds, the viscosity in centipoises \-cas calculated, using the constants determined for this particular Stormer viscometer. A typical series of observations and calculated viscosities follows for a longleaf pine gum analyzing 20.47, turpentine and 4.27, water: Temp O
c.”
60.0 62.2 65.0 66.567.0 69.2-69,s 73.0-72.2 75.5 77.0 79.0
Time, t , for 100 Revolutions, Seconds 273.2 209.9 162 7 134.7 107.7 84.1
Calcd. Viscosity, (3.55f) - 1 i , 5 i , Centipoises 952 727
7 =
560 460 359 281 205 181 156
62.8 56.0 49.0
Similar data were obtained on the other samples of pine gum a t various dilutions with turpentine. These data are plotted in Figure 2. The percentage figures on each curve indicate the con-
Vol. 38, No. 5
centration of turpentine by n-eight. Viscosity measurements made as the temperature increased, and also as it d e c r c a d , revealed no significant diffcrences. ACKhOWLEDGMENT
The authors n-ish to express their appreciation t o S . C. X c Conncll of the A-aval Stores Station at Olustee, Fla., foi the gum samples; and to F. C. Magne of the Analytical, Physical Cliemical, and Physical Division of the Southern Regional Rcwarch Laboratory for the calibration of the viscometer. LITERATURE CITED
(1) Am. SOC.f o r Testing Materials, Standards, P u t 111, p. 293 (1944).
( 2 ) Graff, M.M., IND. ESG.CHEST., AN.IL. ED.,15, 63s (1943). (3) Higgins, E.F., and Pitman, E.C., J. IND. ENG.CHEX., 12, 587 (1920). ( 4 ) Naval Stores Research Div., unpublished method. ( 5 ) Smith, W. C., Reed, J. O., Veitch, F. P., and Sliingler, G. P.,
C , S.Patent 2,254,785 (Sept. 2, 1941).
Active Amyl- Isoamyl Alcohol Svstem J
J
E. R. H-AFSLUND
Joseph E . Seagram 61: S o n s , I n c . , Lotciscille, K y .
VAPOR-LIQUID EQUILIBRIUM AT 760 MM. PRESSURE T h e vapor-liquid equilibrium of the active amyl alcoholisoamyl alcohol system was determined at 760 m m . pressure. The active amyl alcohol, 99.34 mole %, was obtained by repeated fractionations in two Lecky-Ewe11 columns. The jacketed Othmer still used in the study w-as “standardized” on the ethyl alcohol-water system and gave results comparable to reliable literature data. It is shown statistically that the relative volatility and concentration of the two amyl alcohols may be considered independent, and that the best estimate of the relative volatility is 1.0792.
T
HE two main components of fusel oils are active amy1 alcohol (I-rotatory 2-methyl-1-butanol) and isoamyl alcohol (3methyl-1-butanol). Isoamyl alcohol is easily obtained in a pure state from other sources, but active amyl alcohol usually has been obtained from fusel oil. Separation of the two alcohols is difficult by chemical means (16) and results in low yields. Recently fractional distillation in high-efficiency columns has been used to separate the two alcohols ( I S , 1 7 ) . The purpose of this paper is to present vapor-liquid equilibrium data on this binary system of active amyl-isoamyl alcohol. EQUILIBRIUM STILL
Many types of vapor-liquid equilibrium stills are described in the literature; an Othmer still (10, 11,12) was used in this study. The specifications shown in Figures 1and 2 of Othmer’s previous paper (11) were followed in constructing the still. The precision of the equilibrium still and experimental technique were checked by st,udying the “standard” ethyl alcoholwater system. The vapor-liquid equilibrium data on this system indicated that the vapor composition was slightly richer in the
C. L. LOVELI, Piirdtce C n i w r s i t y , Lufayette, I n d .
niore volatile component, ethyl alcohol, than has been indicated in the reliable literature. This discrepancy was of a magnitude of 5 to 10% and v-ould be insignificant for most engineering purposes. I t was possible t o eliminate this slight error in the equilibrium data by the use of heating jackets over the outer vapor surface of the still. Insulated or jacketed stills were suggested by Othmer (IO, 1 1 ) , and such means for reducing internal refluxing have been incorporated into the design of equilibrium stills by other investigators (b, 3, 4, 7, 15). The heating jacket consisted of three separate heating coils-one for the long vertical neck, one for the body of the still lying between the internal heating coil plugs, and one for the body of the still below the plugs. Each circuit was made by winding chrome1 A wire, S o . 27 B. & S. gage, into loops spaced 6/16 inch apart; asbestos stiips prevented the wires from touching the glass surfaces. A thermocouple was placed between two of the middle loopa of each circuit. A heavy wrapping of glass wool on t i p of the heating circuits completed the assembly. Variable transformers were used to obtain proper heat input to the circuits, which were operated so that the temperature indicated by the thermocouples agreed within 3’ with the indicated vapor temperature. ,4t times a slight superheating of the vapor was noticeable and, therefore, vapor temperatures are not reported. The Othmer still thus jacketed gave equilibrium data that were comparable with reliable literature data. Unfortunately, the jacketed Othmer still “standardized” on the ethyl alcohol-water system cracked during subsequent runs, and attempts to repair it proved futile. Another modification of the still was blown in the laboratory which incorporated the features of the previous still found necessary for securing accurate equilibrium data. This still contained two changes in design. One change consisted of putting a single-turn helix in the vapor tube from the neck
INDUSTRIAL AND ENGINEERING CHEMISTRY
May, 1946
557
0.808
I
I
9 1
EQUATION:
d=0.8029
+ 0,00443
KEY LIMITS O F CALCULATED SPECIFIC ROTATION ASSUMING A N ABSOLUTE ERROR OF *0.02°V. IN THE OBSERVED ROTATIONS
x
3 O
OB00
t 0.1544X
0 MOLE
0.2 0.4 0.6 0.8 1.0 FRACTION OF ACTIVE AMYL ALCOHOL
Figure 1. Density us. Concentration of Active Amyl-Isoamyl Alcohol Mixtures -5.78
of the still; this helical turn acted as a thermal expansion joint to relieve stresses set up when the body of the still expanded on heating. The second change was to bring the lead wires to the internal heater through glass seals in the bottom of the still. The elimination of the glass plugs in which the heater leads had been brought through the still body allowed the vapor surface of the still t o be covered adequately by two heating circuitsone for the long vapor neck and one for the body of the still. These changes should not have affected the precision of the unit. REAGENTS
The active amyl alcohol was obtained from commercial fusel oil. The fusel oil was partially dehydrated by salting with sodium chloride, and the remaining wa$er was removed by azeotropic distillation with carbon tetrachloride and ethanol. After dehydration the lower boiling components were removed by distillation in a small glass column packed with Raschig rings. The resulting mixture was fractionated jn two Lecky-Ewe11 (8) columns; one had a packed tube 18 mm. 0.d. and 8 feet in Iength, and the second had a packed tube 3 1 mm. 0.d. and 12 feet in length. Repeated fractionations in these columns produced a 0.9934 mole fraction active amyl alcohol. The active amyl alcohol had a refractive index n2zof 1.41084, a density dt6 of 0.8074, and an observed rotation aa: of -9.553' (1 =' 2). The isoamyl alcohol used in the vapor-liquid equilibrium study was carefully redistilled from Baker's C.P. product in the smaller Lecky-Ewe11 column. The redistilled isoamyl alcohol had a refractive index na: of 1.40937 and a density dz6 of 0.8028. Since the amount of the 0.9934 mole fraction active amyl alcohol available for the equilibrium study was rather small, redistilled mixtures of isoamyl alcohol-active amyl alcohol were also used in the study. These mixtures were obtained by carefully distilling the dehydrated fusel oil in the smaller Lecky-Ewe11 column. The heads material was withdrawn and discarded, and the distillate, a mixture of isoamyl and active amyl alcohols, was collected for the equilibrium study.
I-
Figure 2.
'
\
Specific Rotation us. Concentration in the Active Amyl-Isoamyl Alcohol System
various concentrations were made by mixing known weights of isoamyl alcohol and the 0.9934 mole fraction active amyl alcohol. The following data were obtained in the density determinations: Mole Fraction Active Amyl Alcohol 0 (pure isoamyl alcohol)
0.1456 0.3085
diK Gram/Ml. 0.8028
0.8035 0.8043
Mole Fraction Active Amyl Alcohol 0,6752 0.$390 0.9934
di5 Gram/Ml.
0.8056 0.8068
0.8074
The data are plotted in Figure 1; a linear relationship was assumed, and the empirical equation derived by the method of averages. This equation is d f 5 = 0.8029
+ 0.00443 X
g./ml.
where X = mole fraction of active amyl alcohol SPECIFIC ROTATION
The relationship of specific rotation us. concentration in active amyl alcohol-isoamyl alcohol mixtures was needed t o calculate the concentration of equilibrium samples. The instrument used
DENSITY DETERMINATION
The concentration of the active amyl-isoamyl alcohol equilibrium samples was calculated from specific rotation determinations. One variable in the specific rotation equation is density; therefore, the densities of active amyl-isoamyl alcohol mixtures were determined at 35.0' C. in a Leach specific gravity bottle. The
Figure 3.
Equilibrium Still and Pressure Regulating System
voi. 38, N ~ 5.
INDUSTRIAL AND ENGINEERING CHEMISTRY
sodium vapor lamp was used as the source of illumination, and the temperature was controlled a t 20.0" * 1.0 0.1" C. The average of t'he hundred o b s e r v a t i o n s on t,his sample was 27.5625" Y. From these data the concentration of the high-purity active amyl alcohol can be calculat'ed to be 0.0934 mole fraction active amyl alcohol. Table I gives the observed specific rotations of various concentrations of active amyl alcohol a t 33.0" + 0.1"C. in Mazda light. Fiaure 2 is a plot of specific rotation against coiicentration. The relationship between the two variables appears linear except in the low concentration ranges. The apparent deviation from linearity in the low concentration region is due to the effect of small absolute error5. For example, an absolute error of 0.02" V. in the observed rotation a t a concentration of 0.9934 mole fraction active amyl alcohol would prpduce a 0.076% error whilo the same ab3olute error a t a concentration of 0.0757 mole fraction active amyl alcohol rvould produce an error of 0.99%. i l n equation vas derived by the method of least aquares; the specific rotation-concentration relationship was assumed to be linear, and the deviation froin a linear relationship !vas assume4 to be duc to an error in specific rotation. The two datum points of concentrations below 0.1 mole fraction active amyl alcohol were ignored in determining the equation Constants because of the relatively large percentagp of error they contained. The derived equation is: ,
Figure 4.
Vapor-Liquid EquiliIwium
of the Active Amyl-Isoamyl Alcohol
System at 760 Rlm. Pressure
in the polarimetric analyses was a Schmidt and Haensch saccharimeter, KO. 10804, equipped with a single wedge compensator and a Iippich double-field 0 0. I polarizer. h dichromat,e filter a as used 111 all analyses. A 100-watt 1Iazda lamp was the source of illumination in all measurements n i t h one exception which is noted A 2-dm. jacketed polariscope tube and a thermometer calibrated to 0.02' C. were utilized in the determinations. Constant temperature control was achieved by using a liquid bath equipped with a thermoregulator, resistance heater, cooling coils, and stirrer. The constant temperature system maintained the liquid in the polariscope tube within 0.1" C. of the control point. Known concentrations of active amyl alcohol-isoamyl alcohol were prepared, and the observed rotations determined. Before each set of rotation data was taken, the zero point on the instrument was adjusted so that one hundred consecutive zero point readings averaged less than * 0.01 'Ventzke. One hundred readings of the observed rotation were made on each sample; the side of approach to the zero point ivas alternated every five readings. I n determining the concentration of the high-purity active amyl alcohol fraction, the observed rotation of pure active amyl alcohol reported by Narckwald and AlcKenzie (9) was taken as the standard. They reported a': = 9"37' (2 = 2). I n order to duplicate the essential conditioiis of their analysis, an electric
[ a 1 ~ ~ 5 = 0 ~ -5.8434 .
VAPOR-LIQUID EQUILIBRIU2M
The vapor-liquid equilibrium determinations of the active amyl alcohol-isoamyl alcohol system were made a t 760.0 * 0.6 mm. pressure. The pressure regulator was a simple device used by other investigators and dewibed by Baker and co-workers (2). A cylinder, packed with Drierite, in the line from the still to the pressure reservoir protected the contents of the still from atmospheric moisture. A second cylinder, packed wit,li glaqs wool, protected the still from Drierite dust. Figure 3 shows the oquilibrium still assembly. The technique of operating the Othmer still has been described (II), and therefore only the significant differeiices in procedure will be notea. A minimum recycling time of 3 hours was allowed to attain equilibrium. The heat input to the surface hcnting
TABLE11. OBSERVED ROT.4TIOS, ac, O F T'APOR-IJIQUID EQUILIBRIUM SAMPLES OF ACTIVE AMYL-ISOAMYL ALCOHOL, AND CALCULATED CONCENTRATIONSAIND RELATIVE T'OLATILITIES Liquid-
7 -
TABLE I. COMPARISON O F OBSERVED AND CALCULATEDaVALUES O F SPECIFIC ROTA TI OX^ O F ACTIVEAMYL-ISOAMYL ilLC0HOL MIXTURES Mole Fraction Active Amyl Alcohol 0,9934 0,8409 0.6192 0.4281 0.2850 0.1995 0.0872 0.0757
la]",5,,1. [al::,OL
=
Sp. Rotationb Observed Calculated" - 5.6936 5.6900 - 5.7061 -5.7136 5.7483 5.7478 -5,7870 -5.7773 -5,7979 -5.7984 5.8077 -5.8126 5.8857 -6,8298 - 5.7689 -5.8316
-
-
-
-5.8434
+ 0.1554X degrees.
Deviation, ci 10
- 0 06 + O . 13 -0.01 -0.17 fO.O1 f0.08 -0.95 f1.09
+ 0.1554X degrees
a,
Mole fraction
-2,2120 -2.63i -3.682 -4.474 -5.726 -7.376 -8.452 -9,360 -9,978 -11,368 - 12.830 -13.776 - 14.822 -15.354 - 16,402 - 18.046 -19,951 - 20.984 -22.465 -23.366 - 24.874 - 26.130
0.0818 0,0976 0.1364 0.1688 0.2125 0,2740 0.3143 0.3483 0.3715 0,4237 0.4788 0,5144 0.5540 0.5741 0.6138 0.6763 0.7488 0.7883 0.8449 0.8798 0.9375 0,9888
--
Vapor--------.
a* - 2 . 3R8C - 2.778
-3.964 -4.693 -6.057 -7.836 -8.955 -9.786 -10.458 -11.916 -13.296 -14.262 -15.400 15,880 -16.931 -18,510 -20.320 -21.344 a2.680 -23.541
-
-
- 25,009
-26.155
Mole fraction
Rclative Volatility
0 0873 0.1028 0.1469 0.1741
1.0737 1.0594 f ,0902
0.2248
0.2912 0.3331
0,3643
0.3893 0,4443 0.4963 0.5328 0,5768
0.5941 0,6339 0.6939 0.7629 0,8020 0.8532 0,8862 0.9426 0.9867
I . 0606 1,0747 1,0886 ? . 08'37 i .ai23 1.0794
?,OS75 I . 0726
1,0766 1.0928 1.0858 1.0894 1.0850 1,0794 1.0878 1.0669 1.0669 1.0948 1.0086
INDUSTRIAL AND ENGINEERING CHEMISTRY
May, 1946
uol
,
0
1.09
O0
0
derived equations. Relative volatilities were calculated from the concentrations by the following equation:
..
0
O . 0 0
559
0
Table I1 gives the observed rotations, calculated concentrations, and relative volatilities. Figure 4 is a plot of the vapor-liquid equilibrium data, and Figure 5 is a plot of relative volatility against concentration. T o determine whether a relation existed between relative volatility. and concentration, a linear equation was developed by the method of least squares, making the sum . of the squares of the deviations of relative volatility a minimum: where
CY
a = 1.0766 = relative volatility
+ 0.0053X
I n order to determine whether the derived relationship was statistically significant and not due merely to chance, the standard statistical F test (6) was applied. F was calculated to be 0.55. I n order for the regression to be significant ( 5 ) ,in this case at t h e 5y0 level, F would have to equal 4.35; a t the 1% level F would have to equal 8.10. Therefore, the regression is not statistically significant and may be accounted for by mere chance factors. The best estimate of the relative volatility is, therefore, the mean of the observed relative volatilities which is 1.0792. The standard deviation of this distribution is 0.0104. The limits of the true mean a t the 99% probability level may be expressed (1) as CY
= 1.0792
* 0.0064
The absence of a regression between relative volatility and concentration is a necessary criterion for adhcrencc of the syatern t o Raoult’s law. Vapor-liquid equilibrium of activc amyl alcoholisoamyl alcohol was calculated using 1.0792 ai; the relative volatility and is presented as mole fraction active amyl alcohol: Liquid Concn.
Vapor Concn.
0.0000 0.0500 0.1000 0.1500 0.2000 0.2500 0.3000 0.3500 0.4000 0.4500 0.5000
0 0000 0.0537 0.1071 0.1600 0.2125 0.2646 0.3163 0.3676 0.4184 0.4689 0.5190
Liquid Concn. 0 .$OO 0,6000
Oj6.i00 0.7000 0.7500 0.8000 0.8500 0.9000 0.9500 1.0000
Vapor Concn 0.5688 0.6181 0.6671 0.7158 0.7640 0.8119 0,8595 0.9067 0.9535 1.0000
LITERATURE CITED
(1) Am. Soo. for Testing Materials, “Manual on Presentation of Data”, p. 41 (1940). (2) Baker, E.M., Hubberd, R. 0. H., Huguet, J. H., and Michalowski. S.S., IND. ENG.CHEM.,31,1258 (1939). (3) Bromiley, E.C., and Quiggle, D., tbid., 25, 1136 (1933). (4) Carey, J. S.,and Lewis, W. K., Ibid., 24,882 (1932). (5) Freeman, H. A., “Industrial Statistics”, p. 170, New York, John Wiley & Sons, 1942. (6) Kenney, J. F.,“Mathematics of Statistics”, Part I, pp. 162 & 164,Part 11,pp. 145 & 146,New York, D.Van Nostrand Co., 1939. (7) Langdon, W. M.,and Keyes, D. B., IND.ENQ.CHEM.,34, 938 (1943). (8) Lecky, L. H.,and Ewell, R. H., IND. ENG.CHEM.,ANAL.ED., 12,544 (1940). (9) Marckwald, W., and McKenzie, A,, Ber., 34,485 (1901). (10) Othmer, D. F.,IND.ENG.CHEM.,20,743 (1928). (11) Ibid., 35, 614 (1943). ENG.CHEM..ANAL.ED., 4,232 (1932). (12) Othmer, D. l?., IND. (13) Sohicktans, S. T.,Ettienne, A. D., and Steele, W. J., Ibid., 11, 420 (1939). (14) Smith, D.M.,Bryant, W. M. D., and Mitchell, J., Jr., J. Am. Chem. SOC.,61,2407 (1939). (15) Trimble, H. M., and Potts, W., IND.EKQ.CHEW,27,66 (1936). (16) Whitmore, F. C.,“Organic Chemistry”, pp. 107, 108, 126, 127, New York, D.Van Nostrand Go., 1937. (17) Whitmore, F. C.,and Olewine, J. H., J. Am. Chem. SOC., 60, 2569 (1938). BASEDon a dissertation submitted by E. R. Hafslund t o Purdue University in partial fulfillment of the requirements for the degree of doctor of phi-
losophy.
