Analysis of Binary and Ternary Mixtures System Acetone-Chloroform-Methyl Isobutyl Ketone ANDREW E. KARR', WILLIAM M. BOWESI, AND EDWARD G. SCHEIBEL' Polytechnic Institute of Brooklyn, Brooklyn, N . Y . The limiting factor in the accuracy of phase equilibria data is often the method of analysis, especially for ternary systems. This work was undertaken to provide accurate methods of analysis for determining the binary and ternary vapor-liquid equilibria of the acetone-chloroform-methyl isobutyl ketone system. Accurate physical methods of analysis are presented for the binary and ternary mixtures of acetone, chloroform, and methyl isobutyl ketone. Analyses of ternary mixtures require measurement of any two of the three physical properties: refractive index, densit?, and viscosity; by measuring all three properties a weighted average of the points of intersection on a triangular composition grid can be used to determine the composition. The data presented can be used to determine the composition of mixtures of acetone, chloroform, and methyl isobutyl ketone with average accuracy of about 0.25 mole 76.
T
HE determination of reliable vapor-liquid equilibria data and other phase equilibria data requires accurate analyses of the phases coexisting a t equilibrium, and the results of the most careful evperimental technique may be completely vitiated by inadequate analytical methods. Both chemical and physical methods of analysis have been used for this purpose, depending on the preferences of the investigator and the suitability of the method. If a chemical method of analysis is to be used, i t is necessary to determine whether the methods suitable for the pure components are applicable to mixtures of two or more components. The most commonly used physical methods of analysis are refractive index, density, viscosity, boiling point or vapor pressure, optical density, and freezing point.
Table I.
index, density, and viscosity, the optimum combination of accuracy and convenience would be had. MATERIALS
The materials used in the present work were dried over Drierite and then distilled a t a reflux ratio of 25 to I in a packed column containing the equivalent of 33 plates. The acetone was obtained as a 70% middle cut from Baker's chemically pure product. The methyl isobutyl ketone was also obtained as a 70% middle cut from a special product of Carbide and Carbon Chemicals Corp., which was reported 99.5% pure. The chloroform was obtained as a 60% cut from Baker's chemically pure product after rejecting a 30% forecut to ensure complete elimination of the ethyl alcohol stabilizer. Acetone and methyl isobutyl ketone absorb moisture from the air. They were stored in tightly stoppered bottles and were distilled every 3 to 4 weeks. Chloroform decomposes in the presenw of light and air, liberating hydrochloric acid and phosgene. It was, therefore, stored in tightly stoppered brown bottles, and fresh material was distilled every 2 weeks. Daily checks of the refractive indexes of all materials were made. The physical properties of the materials used, as determined in this investigation, are given in Table I and are compared to what appear to be the most reliable literature values. Boiling points were also determined. DETERMINATION OF PHYSICAL PROPERTIES
Refractive indexes, densities, and viscosities were determined a t 25" =t0.1" C. The temperature was controlled in a water bath equipped with an agitator and a circulating pump, by means of a mercury thermoregulator and an electric relay. The temperature was measured with a crrtified Sational Bureau of Standards thermometer. Refractive Index. Refractive indexes were determined under sodium D light with a Spencer Abbe refractometer which has an acknowledged precision of + 0.0002 unit. However, through the use of a standardized procedure by a single individual, it appeared that somewhat better precision could be realized. The instrument was standardized bv means of a glass crystal of known refractive index. Freshly disPhysical Properties of Rlaterials Used tilled wat.er was used as a riscosity a t 25' C., secondary standard. In addi-
Boiling Point, ' C . Density, d:' Refractive Index, nL5 Centipoise Observed Literature Observed Literature Observed Literature Observed Literature Acetone 56.13 56 10 ( f . 5 ) 0 . 7 8 4 0 0 . 7 8 4 0 (16) 1 . 3 5 6 0 1 . 3 3 5 6 (16) 0 . 2 9 9 0 . 3 0 7 2 (7) 0.7849 ( 7 ) 1.3566 (14) Chloroforni 61.26 6 1 . 1 5 ( 1 : ) 1 . 4 7 8 7 1.4799 (28, 1 7 ) 1 . 1 4 3 0 1,442925.4' ( 1 0 ) 0 . 5 3 0 0 . 5 3 4 ( 7 ) Methyl Isobutyl Ketone 1 1 5 . 9 1 1 1 5 . 8 (3) 0 . 7 9 6 0 0 . 7 9 6 0 (9) 1.3937 1,3959"' ( 7 ) 0 . 5 4 2 0.579920' ( 7 )
cross checks "ere made of the refractive indexes of acetone, chloroform, and methyl isobutyl ketone. In order to minimize evaporation of the volatile solvents while t,ransferring - samples to the refractometer, all samples were chilled in ice water prior to loading. Constant controlled temperatures were established in approsimately 1 minute. Tests showed that a t this constant temperature samples in the refractometer did not change composition for 3 minutes. Therefore no error was introduced by allowing sufficient time for the chilled samples to attain the controlled temperature. Density. Densities were determined by means of 10-ml. captype pycnometers (Ace Glass Co., Catalog 40-5475).
The analytical data presented in this paper serve as a means of determining the composition of mixtures of acetone, chloroform, and methyl isobutyl ketone. Although chemical methods of analysis were considered, no practical chemical method for differentiating acetone from methyl isobutyl ketone was known, and furthermore the determination of chloroform (11) was timeconsuming and gave erratic results in the presence of acetone. Consequently, physical methods of analysis were investigated and after inspection of the differences of the physical properties of acetone, chloroform, and methyl isobutyl ketone, it was concluded that by the use of the three physical properties, refractive
Chilled samples were transferred to the pycnometers which, after 20 minutes in the constant temperature bath, were removed; the overflows were quickly wi ed; the pycnometers were chilled slightly, wiped thoroughly, alowed to come to room temperature, and weighed. The balance %eights were calibrated against
Present address, Hoffmann-La Roche, Inc., Nutley 10, N J. :Present address, American Cyanamid C o . . Stamford, Conn.
1
459
ANALYTICAL CHEMISTRY a standard 10-gram weight. Room temperature was always Icsci than 25' C. so that the liquid never overflowed the capillary.
The pycnometers were calibrated with freshly distilled water having a density of 0.99il gram per ml. at 25' C. Buoyancy
CONSTRICTION-
-3.13
ML
I D E A L M O L F R A C T I O N M.I.K.
AT 2 5 %
Figure 3. Viscosity Deviation from Ideality, System Acetone-Methyl Isobutyl Ketone at
23" c.
-PIPET
in drawing the liquid into the capillary to the etched mark by the application of suction.
-RUBBER STOPPER
A sample to be analyzed was placed in the constant temperature bath for 10 minutes. The loading pipet wits then quickly insertt:d into the test tube, as shown in Figure 1. The pipet \vas filled by applying pressure to the hulb. The carefully meas-
a TUBE
Figure
1.
Loading Device \-i scometer
for
corrections were not applied, inasmuch as they were only significant in the fourth place and cancel out when the density-composition curve is calibrated on the same basis. Densities were determined with a precision of +0.0002 gram per ml. Viscosity. Viscosities were determined by means of CannonFenske-Ostwald viscometers designed for liquids of 0.7 to 1.5 centistokes (2). A loading pipet, as shown in Figure I , was
01
I D E A L M O L F R A C T I O N CHLOROFORM 02 0.3 0.4 0 5 06 07 08
09
Figure 2. Refractive Index Deviation from Ideality, System Acetone-Chloroform a t 25' C. 0 This investigation H Rosanoff and Easely (10)
made which delivered 3.13 * 0.01 ml. a t 25" C. The loading pipet gave better reproducibility and was more convenient than the usual method of loading Ostwald viscometers, which consists
V O L U M E 23, NO. 3, M A R C H 1 9 5 1
46 1
ured sample was then transferred to the viscometer, in which the pipet fitted snugly, thereby minimizing evaporation losses. Both arms of the viscometer were stoppered for 5 minutes to :illow the liquid to reach the bath temperature. By the application of air pressure, the liquid was forced into the capillary slightly above the etched mark. The,viscosity in seconds was then measured in the urual manner by means of a precision electric timer having 0.1-second divisions
Table 11.
Physical Property Calibration of Binary Systems
Acetone Mole Fraction
0.9323 0.8350 0,8344 0.7731 0.7067 0.6923 0.5275 0.5077 0.4615 0.3590 0.3526
s5
Density,
dz5
Acetone-Chloroform System 0.8486 1.3640 0.8639 0.9194 1.3730 0.9418 1.3760 1.0137 1.3850 1.0223 1.3862 1,0775 1.3941 1.1130 1.3978 1.1255 1 3992 1.2166 1.4110 1 ,41.-21 1.2499 1,3219 1 .i-ao 1.3298 1,3929 I .JX27 1.4419 1438.5
0 9140 0.8932 0.8185 0.7869 0,6892 0,6769 0.5979 0.5507 0.5327 0.4008 0 . 3 5 17 0,2455 0.2329 0.1339 0.0603 0.9630 0,9233 0.8196 0.6793 0.5520 0.4960 0.3737 0.2192 0.0555
Triplicate determinations within 0.2 second were usuallj obtained. This corresponds to a precibion of 0.2 to 0.1% of the visc*osityfor the mixtures encountered in this investigation Large deviations in the triplicate readings indicated foreign obstructions I I I the capillary; these determinations were repeated.
Refractive Index, n
... ... ..
... .. ...
...
... ... ... ... ... ...
.4oetone-%fethyl lrobutyl Ketone Systeiii 1,3600 ... 1,3650 ... 1.3651 ... 1,3681 ... 1.3713 ... 1,3718 0.7906 1.3787
0.2689
0.1842 0,0872
Viscosity a t 250 c.. Seconds
. .
1 0 i .5 104, .5 106.0 108.8 111.7 112.6 112.8 109.4 101 x
109.7 117.2 117.fi 122.-1 127.3
...
...
143:j
1.3841
0.7924
1.3867 1.3891 1.3916
15517 156.5 163.8
...
179: 5
1 ,3808
... ... ...
Chloroforin-Methyl Isobutyl Ketone System Chloroform Mole Fraction 0.9657 0.9429
o.,5?
I
0:I
0:2
0:3
0:4
0:s
0:6
0:7
0:8
0,8979 0.8652 0.8390 0.7985 0,7544 0.6975 0.6386 0.6143 0,5473 0,5333 0.4321 0.3617 0,2445 0,1858 0.1420 0.0662 0.9291
0:s
0,8640
MOL F R A C T I O N ACETONE
0,7282 0.6114 0.4970 0,3916 0,2352 0.1599 0,0813
Figure 5. Ternarv Densitv Calibration. Svstem ~ ~ t o n e - C h f o r o f ~ r m - ~ l e tIsobutyl hyl I
