A STUDY OF T H E TERNARY SYSTEM: CARBON TETRACHLORIDE, ALCOHOL AKD WATER BY HARRY A . CURTIS A N D ESBON Y . TITUS
Introduction Carbon tetrachloride and alcohol are miscible in all proportions, as are also alcohol and water. U'ater and carbon tetrachloride, however, dissolve in each other only in very small amounts. A mixture of the three liquids forms either one or two layers, depending upon the relative proportions of the three components present and upon the temperature. If the ternary system be represented in the usual way, Fig. I, there will be a certain region, that shaded in the figure, within which two layers will exist, all mixtures not represented by points within the shaded area forming but one liquid phase. Since the mutual solubility of liquids is, in most cases, increased by increasing the temperature, c the critical solubility curve, CzHgOH a b c, will approach the Fig. I CC14-H20 line as the tempcirature is raised. If temperatures be represented in a direction at right angles to the plane of the triangle the equilibrium between the one and two phase systems will be represented by a surface sloping toward one side of the right prism. The first part of the present paper locates the curve a b c for the isotherm 19.75', and also locates several lines in the critical temperature surface from which the shape of the surface may be inferred. The second part of the paper contains a study of the density and index of refraction of various homogeneous mixtures of the three components. It was at first thought that sufficient data concerning density and refractive index could be gathered to make
740
Harry
A. Curtis
Esb0.l.z k'. Titus
possible the analysis of any homogeneous mixture of carbon tetrachloride] alcohol and water by simply determining the value of these two properties for the unknown mixture. As the work progressed, however, it became evident that even after the immense amount of necessary data had been obtained] the problem would still remain indeterminate for certain mixtures, as will be shown later. These measurements were therefore discontinued after sufficient data had been taken to show the change in density and index of refraction for any given change in composition of the system.
Chemicals Used The alcohol was prepared from the laboratory supply of absolute alcohol. This was further dehydrated for two weeks with anhydrous copper sulphate and twice distilled, the middle fraction of the distillate being taken each time. Kahlbaum's carbon tetrachloride was used. It was first distilled] the middle portion allowed to stand over fused potassium hydroxide for a week, and then redistilled. The part used all distilled over within less than one-tenth degree range. The water used was distilled. Critical Solubility lata The critical solubility curve a I c for the 1 9 . 7 5 ' isotherm was determined as follows : Six different mixtures of carbon tetrachloride and water were made up, the amounts of each component being accurately weighed. These mixtures were placed in large test tubes and brought to 1 9 . 7 5 ' in a glass thermostat. Alcohol was then added from a weight burette to each mixture in turn, the mixture being vigorously stirred meanwhile, until the critical point was reached. A t the critical point the mixture becomes homogeneous. The various critical concentrations are recorded in Table I, and the results are shown graphically in Fig. 11. The points i n Fig, I1 marked thus: 0 were obtained by interpolation for 1 9 . 7 5 ' from Fig. 111. I t is not to be expected that these points are as accurately located as those determined for the isotherm.
Carbon Tetrachloride, Alcohol and W a t e r
74'
TABLEI Temperature I y .7 jO ~
Percent CC14
~
Percent C?H,OH -~
50 50
43 IY 51 Y5 17 6 8 50 Yi j~ j6
Percent HzO -
~
____
24.04 14.8; 31 .Oj Iy.2j
38.jo 31.42
Fig. I1
The curve a b c intersects the CC1,-H20 side of the triangle very near the corners, water and carbon tetrachloride being almost immiscible. Rex' gives the solubility of carbon tetrachloride in water as 0 . 8 g per liter at 20'. This value must be considered as only an approximation, however, since his method did not take into account the solubility of water in carbon tetrachloride. The effect of temperature on the mutual solubility of l
Zeit. phys. Chem., 5 5 , 355 (1906)
Harry A. Curtis and Esbox Y.Titus
742
the components, i. e . , the shape of the critical solubility surface, was studied as follows: To a known mixture of two of the components, the third component was added in small amounts from a weight burette until, on lowering the temperature, separation into two layers occurred. The critical solubility temperature of this mixture was then determined by raising and lowering the temperature through the critical point several times. A further amount of the third component was then added and the critical solubility temperature again determined. These operations were continued until, a t the higher temperatures, the volatility of the carbon tetrachloride prevented further accurate measurements. It is evident that all the concentrations in this series lie in a straight line drawn from that point on the side of the triangle which represents the original binary mixture to that corner of the triangle which represents the third component, such a line as I in Fig. 11. Consider a plane containing this line and standing at right angles to the plane of the triangle; the various critical solution temperatures plotted against the corresponding amounts of the third component will give a curve lying in this plane and representing the intersection of the plane
TABLE I1
I
I1
Ratio CClA, CzHjOH ~~
=
0.5048
Ratio CC14,’C2HjOH= 1.0646
~~ ~
Percent H ~ O
24.25 24.61 25 I3
1 ,
Crit. sol. temp. -I
. 8 O
Percent H?O
12.47
’
t-3.6 10.6
25.64
17.0
14.85
26.14 2 6 . j9 27.Ij 27.71 28.5 2
24.5 28.55
15.3 1j.67
31.45
16.02
1
32.751 35.5
S o t accurate; CC1, distilling OR.
13.95
14.45
Crit. sol. temp. 2.03O
23.9 29.8 35.4 39.55 42 75 -1.5.5
Carbopi Tetrachloride, Alcohol a n d bVater
743
TABLE11-( Continued) I11 Ratio CC1, 'C2H6OH = -
Percent H1O
6 .S I 7.16
IV Ratio CC14/H20
2.1012
Crit. sol. temp.
Percent C?HjOH
= 1.0922
Crit. sol. temp
44 S C 42 2
I2.TC
2I.jj
39.5 3j.I 30 6 2s
4
'9.9 14.6 9 . '5 I .6
Fig. 111
with the critical solubility surface. B y determining several of these intersection curl-es, beginning with different binary mixtures, the general shape of the critical solubility surface may be inferred. In Fig. 11, the lines I, 11, I11 and IV represent the various series of ternary mixtures used. Table I1 gives the various critical solubility temperatures and thc,
Harry A. Curtis and Esbon I/. Titus
744
corresponding compositions, while Fig. I11 shows graphically the intersections of the planes containing the lines I, 11, I11 and IV of Fig. I1 with the critical solubility surface. It will be noted that the percentages of water and of alcohol in Fig. I11 are plotted on a very much larger scale than is used in the triangle. This was done in order to show more clearly the effect of temperature on solubility. The critical solubility surface rises very abruptly from the triangle, i. e., temperature has very little effect on the mutual solubility of the three components. Refractive Index and Density The determination of refractive index and density were naturally limited to such ternary mixtures as form but one liquid phase at the temperature used, i. e., to such mixtures as would be represented by points lying within the unshaded area of Fig. I. Various mixtures of two of the components were made, and to each of these in turn varying amounts of the third component were added, refractive index and density being taken on each ternary mixture thus obtained. The compositions of the ternary systems used are shown on Curves V, VI, VII, etc., of Fig. IV. Tables 111, IV, V, etc., CCla
CzH50H Fig. 11-
Carbon Tetrachloride, Alcohol avld Water
745
TABLEI11 Series V of Fig. IV. -
_~
~_
Ratio CClr 'C2H50H
Percent CCld
Percent C?HbOH
_ _
~
~
~-
=
Percent H20
~
0.05086
________
.~ _~
~
Density
Index I
-
-
I
1.84 4.30 4.17 3.86 3.57 3.05
95.16 84.45 82 .oo 75,93
2.71
70.28
26.15
59.97 53.17
36.98
0.8121 o 8422 0.8485 0.8634 0.8768 0.5004
44.12
0.9148
0.0
11.21
13.83 20.21
.3637 ,3662 I . 3664 I ,3665 I ,3661 I .3646 I .3630 I
I
TABLEIV Series VI of Fig. IV. .._ __ -
_
~
-
Percent cc14' Percent ClHsOH
I
Ratio CCIr/C2HjOH
=
0.1096
-
Percent H20
Density
00 1 1 13
0.8339 0.8619 0.8791 0.5156
Index
I
9 88 8 78
8 6
90 1 2 80 09 73 06 56 60
01 21
18 93 37 I 9
I ,3665
,3687 ,3684 1 3659
I I
'
TABLEV Series VI1 of Fig. IV.
_
-
-
Percent cc14
20,35 19.45 18.78
17.38 15.58 15.14 14.36
Ratio CC14/C2HaOH __ ~
Percent GHbOH
79.65 76.11 73.47 68.02 60.96 j5.26
=
0.2555
_
Percent H20
~
Density
'
Index
0 0
4 44 7 76
14.60 23 46 2 5 60 ' 9 44
