INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1955
Subscripts L refers t o liquid phase o refers to vapor phase 1 refers t o more volatile component, methylcyclohexane 2 refers t o less volatile component, toluene LITERATURE CITED
(1) Beatty, H. A., and Calingaert, G., IND. ENG. CHEM.,26, 904 (1934). ~----, (2) Carlson, H. C., and Colburn, A. P., Ibid., 34, 581 (1942).
457
(3) Driesbach, R. R., "Physical Properties of Chemical Substances," Dow Chemical Co., Midland, Mich., 1952, ' (4) Othmer, D. F., IND.ENG.CHEM.,ANAL.ED.,20, 763 (1948). (5) Rossini, F. D., and coworkers, Natl. Bur. Standards, Ciro. C461 (1948) ; American Petroleum Institute Research Project 44. (6) Quiggle, D., and Fenske, M. R., J. Am. Chem. SOC.,59, 1829 (1937). (7) Van Lsar, J. J., 2. phys. Chem., 72, 723 (1910). (8) zbid., 185,35 (1929)., RECEIVED for review May 11, 1954.
ACCEPTED October 18. 1954.
Azeotropes of 2-Butoxyethanol with Alkyl Benzenes
c
WILLIAM F. KIEFFER AND RICHARD A. HOLROYDI The College of Wooster, Wooster, Ohio
T
HE monoethers of ethylene glycol are known t o be com-
pletely miscible with hydrocarbons, yet t o form solutions whose positive deviations from Raoult's law are of sufficient magnitude t o form minimum boiling azeotropes. The azeotropes of 2-ethoxyethanol with homologous alkyl benzenes have been reported (3) and have been shown t o follow closely the correlation proposed by Skolnik ( 6 ) . This research reports the comparable series of azeotropes between the higher boiling 2-butoxyethanol (171.2' C.) and the correspondingly higher boiling hydrocarbons from cumene (152.4O C.) t o n-butylbenzene (183.4' C.). Lecat ( 4 ) tabulates data for azeotropes with mesitylene, p-cymene, and n-butylbenzene. Horsley ( 2 ) includes these and IO0
I
I
I
I
I
I
I
I
l
90 80700050
W
-
40 -
a
0
30-
hl
4
z 20
-
W
3 v) 0
2
j 100
f
180 160 170 150 BOILING TEMPERATURE OC.
X Lecat data
MATERIALS AND APPARATUS
The 2-butoxyethanol was obtained from t h e Carbide and Carbon Chemicals Co., Union Carbide and Carbon Corp. The butylbenzenes were provided by the Phillips Petroleum Co. through the courtesy of Fred Frey. The Paragon Division, Matheson Co., Inc., was t h e source of t h e p-cymene and oxylene. Mesitylene was from the Eastman Kodak Co. -411 materials were purified by distillation in a Todd fractionation assembly (7') operated at a reflux ratio of 10 to 1 . Pressure on t h e column was maintained at 760 =t1 mm. b y a manostat device. Mesitylene and o-xylene were also purified by fractional crystallization. Samples boiling within less than a 0.1' C. range were utilized. T h e normal boiling temperatures agreed within 0.1' C. with those re orted by t h e American Petroleum Research Project 44 (1).. #h e refractive indices, measured with a precision of f0.0002 on an Abbe refractometer thermostated a t 20" f 0.1 ' C., duplicated t h e published values except for a variation of f0.0004 for n-butylbenzene, - 0.0007 for p-cymene, and - 0.0007 for mesitylene. T h e procedure followed was to survey each binary system to determine vapor-liquid equilibria compositions at prevailing atmospheric pressures, usually about 740 mm. A Rogers, Knight, and Choppin ( 5 ) apparatus was used with either a fractional degree thermometer or a Beckmann thermometer. The refractive index of each sample was referred to prepared calibration curves for each system t o determine compositions. After each azeotrope concentration was ascertained from t h e conventional plots (vapor composition vs. liquid composition), it was confirmed for pressures of 760 mm. A 20-ml. sample of t h e azeotrope was prepared and distilled in the same Todd column t h a t was used for t h e purification of t h e starting materials. The temperature for t h e constant boiling mixture was determined to f0.05' C. The limit of error in evaluating compositions was f0.3 mole yo. All temperatures were read on thermometers calibrated against a National Bureau of Standards certified thermometer graduated in 0.1" C.
I
190
Figure 1. Azeotopes of %-butoxyethano1 with alkyl benzenes correlated by the method of Slcolnik
0 This research
data from Lecat on mixtures with propylbenzene and pseudocumene (1,2,4trimethylbenzene). T h e systems with mesitylene, p-cymene, and n-butylbenzene have been reinvestigated and those with see-butylbenzene, terl-butylbenzene, and cumene have been studied. Attempts t o identify a n azeotrope with the low-boiling o-xylene (144.4' C.) were inconclusive and tend t o confirm the expectation that 2-butoxyethanol boils too high (171.2" C.) to be an azeotrope former with this hydrocarbon.
RESULTS
The data for six azeotropes are summarized in Table I and presented graphically in Figure 1. Azeotrope composition is 1 Present address, Department of Chemistry, University of Rochester, Rochester, N. Y.
INDUSTRIAL AND ENGINEERING CHEMISTRY
458
Vol. 47, No. 3
The curved dotted line of Figure 1 is drawn through the boiling temperatures of the pure hydrocarbons. Its intersecAzeotrope P u r e Substance Mol. 70 wt. yo tion with the straight line around 145O C. Formula Name t b 760 ng t b 760 Cellos. Cellos. ng suggests t h a t alkyl benzenes boiling 171.2 ... ... 1.4196 32 2-Butoxyethanol ( b u t y l below this point will not form azeoCellosolve) 144.4 Quasi azeotrope o-Xylene (1,2-dimethvl1.5054 tropes with this Cellosolve. An attempt benzene) was made t o find a n azeotrope for the 151.7 10.6 10.3 1.4834 152.4 Cumene (isopropylbenzene) 1.4916 162.0 Mesitylene (1,3,5-tri164.6 1.4987 33.2 32.8 1.4719 binary system with o-xylene, which methvlbenzene) 169.1 1.4925 164.4 42.2 30.1 1.4635 tert-Butylbenzene boils a t 144.4' C. The results of frac166.0 47.9 1.45fl 173.3 1.4902 51.2 see-Butylbeneene tional distillation of hydrocarbon-rich 1 7 7 . 2 1 6 7 . 4 5 6 . 6 1.4502 1.4902 59.7 p-Cymene (1-methyl-4-isopropylbenzene) mixtures indicated t h a t the boiling 183.4 1.4902 169.6 75.5 73.4 1.4395 n-Butylbenzene point of the hydrocarbon was depressed less than 0.1" C. to allow a solution of 3.5 to 5% butyl Cellosolve to distill off correlated with boiling temperature by the straighbline equaas the more volatile component. It was not possible t o get conclusive vapor-liquid equilibria data for mixtures richer tion: log z = 0.0479 (273.1 L)- 19.33 in hydrocarbon than this. The corresponding data for mixtures richer in butyl Cellosolve shown on a plot of vapor where 2 = mole % ' 2-butoxyethanol in the azeotrope boiling a t composition us. liquid composition indicated a tangential aptsZ, 'C. The three pertinent data reported by Lecat are indiproach to the ideal line. These observations confirm Lecat's cated on the figure. His tabulation gives azeotropes for nidentification of this system as a case of zeotropy, but also sugbutylbenzene, 81 mole yo boiling a t 170.2' C.; for p-cymene, 63 gest that it should be classified further as an example of what he mole yoat 168.0' C.; and for mesitylene, 32 mole % a t 162.0' C. calls "quasi azeotropy." This research agrees closely only with the last data. The p-cymene discrepancy may be due t o the contamination of LeLITERATURE CITED cat's starting material, as he reports the boiling point of the pure hydrocarbon to be 176.7" C. compared to the API value of dmerican Petroleum Institute Research Project 44, pp. 71, 72, Garnegic Press, Pittsburgh, Pa., 1953. 177.2' C. This is less likely to be true of his n-butylbenzene, EIorsley, L. H., Advances in Chem. Sei-., No. 6 (1952); Anal. Chem., as he used a starting material boiling at 183.1' C., only 0.2" C. 19, 508 (1947); 21,831 (1949). below the API figure of 183.3' C. Leoat gives no refractive Kieffer, W. F., and Grabiel, C. E., IND. EKG.CHEM.,43, 973. index data for comparison. (1951). Although the boiling temperatures of samples used in this reLecat, M., "Tables Azeotropirlues," 2nd ed., Vol. I, p. 148, search agreed with the published standards, the refractive index Uccle-Bruxelles, 1949. discrepancies euggested some contamination. The fact t h a t Rogers, J. W., Knight, J . W., and Choppin, A. R., J . Chem. both sets of data lie on the straight line of the figure indicates Educ., 24,491 (1947). that any contaminants in the starting samples used either in this Skolnik, H., IKD. ENG.CHEM., 40, 442 (1948). Todd, F., IND.ENG.CHEM., ANAL.ED.,17, 175 (1945). research or Lecat's were probably homologous alkyl benzenes. For the three previously unreported azeotropes, the high purity RSCEIT-ED for rel-iem August I O , 1954. ACCEPTEDOctober 21, 1954. of the starting materials is indicated by the agreement of both Rased on t h e senior thesis of Richard -4. Holroyd, submitted in partial fulthe boiling temperatures and the refractive indices with the fillment of the requirements for the ACS Certified B.A. degree i n the Independent S t u d y Program a t the College of Wooster, J u n e 1952. standard data. Table I.
Azeotropes of 2-Butoxyethanol with Alkyl Benzenes ~
~
+
Densities of Ternary System Nitric
Acid-Dinitrogen Tetroxide-Water ROBERT W. SPRAGUE' AND ETHEL KAUFMAN Inorganic Chemistry Brunch, Research Department, U . S . A'uval Ordnance Test Station, Inyokern, Calif. REVIEW of the literature shon s a marked lack of data on the density of nitric acid systems, particularly a t temperatures above 30" C As density data are required in connection with many uses of these systems, thP Research Department of the U. S. Naval Ordnance Test Station in the spring of 1953 undertook a study of the densities a t atmospheric pressure of the ternary system nitric acid-dinitrogen tetroxide-water for eompositions containing more than 75% by weight of nitric acid in the temperature range 35" to 65" C. It is felt that the dilatometric method used has largely overcome errors due to chemical instability of the acids, as the data obtained are in good agreement with existing data a t lower temperatures 1 Present address, D e p a r t m e n t of Chemistry, The Ohio S t a t e University Columbus 10, Ohio.
PREPARATION OF MATERIALS
Nitric Acid. Nitric acid was prepared by vacuum distillation at room temperature from a mixture of potassium nitrate and concentrated sulfuric acid, and was stored a t -40" C. until used. Dinitrogen Tetroxide. Dinitrogen tetroxide was prepared by the method of Whittaker and coworkers ( 6 ) , except that two ground joints were used in an otherwise all-glass system. Water. Distilled water from the laboratory supply line was used for dilutions. This water contained conductive material equivalent t o about 1.5 to 2 p.p.m. Preparation of Mixtures. The composition area of interest was covered by dilution with water of various stock solutions of nitric acid-dinitrogen tetroxide. In this fashion, a constant ratio of nitric acid-dinitrogen tetroxide was maintained for several samples. Special bottles, made with t h e male end of a ground joint for a neck, were used for storing the stock solutions a t -40" C. The compositions of the stock solutions and i?iiytures were determined by weighing the amounts of the various
