Solubility Data for the System Aniline-Toluene- Water JULIAN C. SMITH AM) ROGER E. DREXEL E. I. du Pont de Nemourr & Company, Inu, Wilmington, Del. Solubility data are prennted for the ternary syrtem aniline-toluene-water at 25' C. The distribution between organiu and aqusour pha- ir wrrelated by an empirical exponential function, whiah fits the data more alosaly than a hyperbolia lunation of the type developed by Vartarearinn and Fenake (8).
I THE
N course of a procea investigation, data were necassary on the distribution of aniline between toluene and water. The system anilinetoluene-water waa studied by Riedel (6)in 1906, but distribution data were not determined for high conoentrations of aniline in the organic phase, and solubility of water in the organic phase waa not measured. The present study waa undertaken to supply this miming information. The aniline waa twice distilled under vacuum, and after drying over solid sodium hydroxide, had a spWic gravity of d61,0166, and a refractive index at 25' C. of 1.6840. "he toluene was fractionatad through a short packed column, and the fraction boiling between 110.6 and 111.0' C., at 772 mzn. of mercury, used in the subsequedt experiments. It had a specific gravity of d:' 0.8616 and a refractive index at 26' C. of 1.4928. Dietilled water from the laboratory waa used. Limiting eolubilities in the organic phase were determined by pipetting known amounta of aniline and toluene into amall glerapstoppered Erlenmeyer flasks tb give a total volume of about 80
cc. Water waa then added until a slight turbidity remained after thorough shaking. Any small exow of water waa allowed to separate, and the organic phase waa carefully sampled with a pipet. The samplea were analyzed for water, using the Karl Fischer method, The refractive index waa determined with an Abbe refractometer. Data so obtained were plotted as shown in Figure 1, and solubility of water in other known mixtures of d i n e and toluene was obtained from the refractive index. Solubilities in the water layer were determined by titrating known mixtures of aniline and water with toluene from a microburet. With 100 cc. of aniline and water, however, such small quantities of toluene were involved that this method merely showed the selubility of toluene to be below 0.06% in all cases.
TOLUENE
A
0
%LlBLlTY DATA DISTRlBUTlON DATA
. w
-z i z
6
d
i-
W
t
k
s
W
U
u W a
i-
i-
V
2
w
I
:
K w
I
I-
a
w
Figure 2.
r I?
r"
Solubility Diagram for the System AnilinsToluene-Water at 25' C.
Data on limiting solubilitiea and corresponding refractive indices at 26' C. are given in Table I and plotted in Figure 1. Solubilities of water in toluene, toluene in water, and aniline in water were taken from Seidell (6). The solubility of water in aniline at 25' C. was determined analytically. The present value agrees with the one given by Applbey and Davies ( I ) ,but not
nY Figure 1 . Composition of Organic Layer us. Refractive Index at 25' C.
601
VoL 37, No. 6
INDUSTRIAL AND ENGINEERING CHEMISTRY
602
where A , = percentage of aniline in water la er A , = percentage of aniline in organic t y e r The solid line in Figure 3 represents the distribution as calculated from Equation 1. This equation applies, with a maximum error of 2.5%, between 10 and 90% aniline in the organic phase, A fair correlation of data is obtained by the equation:
zLI
A,
- WEIGHT PERCENT ANILINE IN ORGANIC LAYER
0.0881 A,,
- 1 + 0.0159 A,,
A -
(2)
which is the type developed by Varteressian and B'enske (8) for the system anMne-methYlcYclohexanen-heptane. Equation 2 is represented by the dashed line in Figure 3. The distribution data of Varteressian and Fenske obey exponential equations similar to Equation 1about as well as they do hyperbolic equations similar to Equation 2. Neither present data nor the data of Varteressian and Fenske obey the distribution equation given by Bachman ($), or the mass-law type of equation given by Bancroft and Hubard (S), both of which are empirical, but which apply to a large number of ternary systems composed of two miscible pairs of liquids. Apparently these equatiom do not generally apply to systems consisting of two immiscible pairs. Relatively few systems of this type have been studied, and no general correlation has been found.
Figure 3. Distribution of Aniline between Toluene and Water a t 25" C .
with those of Sidgwick, Pickford, and Wilsdon (7), or Hill and Macy (4). All the previous determinations were synthetic. An inversion of the position of the two layers occurs at about 90% aniline in the organic phase. At concentrations of aniline above 90%, the organic layer is the heavy phase: at lower concezltrations of aniline, the water layer is the heavy phase. The tie lines were determined by making up known mixtures of aniline, toluene, and water in the area of heterogeneity, having a total volume of about 250 cc. The mixtures were thoroughly shaken and allowed to settle. The refractive index of each layer was then determined, and the water layer analyzed for aniline, using nitrous acid and starch iodide test paper. From these analyses and the graphs given in Figure 1, the distribution data given in Table I1 were calculated.
TABLE I. LIMITINGSOLUBILITIES AT 25' C. Aniline
Composition, Weight % Toluene
94.96 88.21
82.38 77.18
:
7i is 68.63 66.01 61.72 58.78 53.63 43.79 31.93 19.05 8.61 0.00
3.66 2.96 1.99 1.01 0.00 0 By analysis. b Leae than 0.06%.
Water
n %5
Organio Layer 6.05' 4.30 3.63 3.14 3.07" 2.52 2.23 1.85 1.57 1.29' 0.36 0.484 0.24 0.09° 0.06 0.05 (6)
1.5712 1.5675 1,5632 1.5594 1.5590 1,6540 1.5512 1,5473 1 ,5444 1.5403 1.5358 1.5287 1.5185 1 5078 1:498? 1.4923
Water Layer 96.34 (6) 97.04 b 98.01 b 98.99 0.049 99.951(6)
1.3400 1.3383 1.3362 1.3340 1.3320
0.00 7.49 13.99 19.68
2i:ii 29.14 33.14 36.71 39.93 46.61 66.73 67.83 80.86 91.33 99.96 0boo
TABLE11. DISTRIBUTION DATA AT 25" C.
'
Original Mixture , Organio Layer "t..% Wt. % Wt. % Wt..% Wt. % ng aniline toluene water aniline water 19.41 3.34 77.25 78.7 3.3 1.5605 16.79 6.70 77.51 65.1 1.9 1.6477 11.93 10.12 77.96 50.7 0.7 1.5336 7.99 13.67 78.44 34.0 0.25 1.6200 4.03 17.06 78.91 15.6 0.07 1.5048 Toluene in water layer always below 0.06%. b B y analysie.
Water Layer" aniline Wt. % ny * 3.lb 2.7b 2.3) 1.96 1.2b
1.3384 1.3378 1.3372 1.3369 1.3344
Because of the low solubilities it is difficult to use data as p r e sented in a conventional ternary diagram (Figure 2). The composition of organic and aqueous layers in equilibrium may best be obtained from Figures 1 and 3, or Figure 1 and Equation 1. For example, an organic layer containing 75% aniline will contain 2.9% water, as shown in Figure 1, and 22.1% toluene. From Figure 3, an organic layer containing 75% aniline will be in equilibrium with an aqueous layer containing 2.97% aniline. Thus, assuming that the aqueous layer contains o.o5yO toluene, an organic layer containing 75% aniline, 2.9% water, and 22.1 yo toluene will be in equilibrium with an aqueous layer containing 96.98% water, 2.97% aniline, and 0.05% toluene. ACKNOWLEDGEMENT
Figure 2 shows the ternary solubility diagram. Tie lines pass through points representing the composition of the original mixtures, showing that material balances were good. The equilibrium concentration of aniline in the water layer is plotted against its concentration in the organic layer in Figure 3. The data given by Riedel (6) are included for comparison. CORRELATION OF DATA
There is excellent agreement between both sets of data. The distribution of aniline between the two layers is defined closely by the equation: A, = 0.239 (A,)O.*s*
(1)
The authors wish to thank R. T. Morris, who did the analytical work. LITERATURE CITED
(1) Appelbey, M.
P.,and Davies, P. G., J. Chem.
SOC. (London),
127, 1836 (1925). (2) Bachman, I., IND.ENO.CHEW, ANAL.ED.,12,38 (1940). (3) Bancroft, W.D.,and Hubard, S. S., J . Am. Chem. Soc., 64, 347 (1942). (4) Hill, A. E., and Macy, P., J. Am. Chem. SOC.,46,1132 (1924). (6) Riedel, R., 2.physik. Chem., 56, 243 (1906). (0) Seidell, A., "Solubilities of Organic Compounds", 3rd ed., Vol. 2, New York, D. Van Nostrand Co., 1941. (7) Sidgwiok, N.V., Pickford, P., and Wilsdon, B. H., J . Chem. SOC. (London), 99, 1122 (1911).
(8) Varteressian, IC. A., and Fenske, M. R., IND. ENO.CHIM.,29, 270 (1937).
