T H E VOLUME CHAKGES ATTETU’DANT ON MIXING PAIRS O F LIQUIDS BY JOHN BUTTERS PEEL, WALTER MATTHEW MADGIN, AND
HENRY VINCENT AIRD BRISCOE
It has been held’ that the changes in volume and temperature occurring when liquids are mixed are closely related. It has been shown, however, ( I ) that a decrease in volume may accompany a fall in temperature, and that even when a decrease in volume is associated with a fall in temperature the maxima of these effects may occur with mixtures of different compositionsZ and ( 2 ) the diminution in volume in a given case (chloroform: ether) was much less than the heat of mixing would suggest. From a consideration of several cases, Young‘ concluded that “the thermal and volume effects do not, in many cases, run pari passu, though where a rise of temperature accompanies an increase in volume, or vice versa, both effects are relatively small.” Though two investigations5 have dealt with the relationship between changes in volume and in other physical properties, none has yet dealt systematically with the possible ronnection between volume change and thermal effect in binary mixtures. It was, indeed, a prior condition of such a n investigation that a broad survey should be made of the sign and magnitude of the thermal effects in a large number of cases, and this has but recently been done.6 It has now been possible to select a numer of pairs of liquids covering a wide range of thermal effects, and for these to determine in a systematic fashion the variation of change of volume on mixing. The results of this work are given here. Experimental The volume changes for each liquid pair were found by determining the densities of the pure liquids and several mixtures of known composition, using 30 cc. silica Sprengel pyknometers having a bulb on the short limb and ground silica caps on both limbs to prevent evaporation. Irregular results obtained at first with both glass and silica pyknometers were traced to changes in the composition of liquid mixtures by fractional evaporation during filling by suction. Possibly such evaporation effects account for the very irregular results previously obtained for some liquid pairs (e.g., Bussy and Buignet for ethyl alcohol: carbon disulphide). Therefore, in the determinations recorded, the pyknometer was filled by forcing the liquid into it from a closed vessel in a See E. G. Guthrie: Phil. Mag., ( 5 ) 18, 495 (1884); Patterson and hlontgomerie: J. Chem. SOC.,95, 1136 (1909). Bussy and Buignet: Ann. Chim. Phys., (4) 4, 5 (1865). a Clarke: Physik. Z 6 154 (1905). 4 “Distillation Prinzipies and Processes” (1922). ‘Brown: J. Chem. SOC.,39,202 (1881); Bramley: 109,434 (1916). Briscoe and Madgin: J. Soc:. Chem. Ind., 46, 107 (1927). 285
2 86
J. B. PEEL, W. M. MADGIN, AND H. V. A. BRISCOE
manner similar to that described by Briscoe, Robinson and Stephenson, the vessel B being replaced by a large test-tube fitted with a rubber stopper carrying the tubes P and H. A mercury-filled Hempel burette was used to apply air-pressure through H.
-X
2.F) 0.5 r
I
I
I
1
-X
I
50% A
1
IOO%A
FIG.I
I n preparing the liquid mixtures (approximately so cc. for each experiment) the proper quantity of the more volatile liquid was weighed into a well-stoppered concial flask, and a measured volume of the second liquid was run in while the flask was kept cooled in running water. Thereafter the flask J. Chem. Soc., 129, 731 (1926) Fig. 3.
VOLUME CHANGES ON MIXING PAIRS OF LIQUIDS
287
was immediately closed, and reweighed, the weighings being made against a tare and with all usual precautions. From the weight-composition of the mixture thus determined, the volume-composition was calculated, using the ascertained densities of the pure liquids.
-X
FIG.2
The pyknometer, after filling, was brought exactly to z j" i .OI in a thermostat, the level of the liquid was adjusted in the usual way, the caps were fitted, and then the pyknometer was transferred to the balance case a n d weighed accurately against its tare. Results. The results are shown graphically in Figs. I and 2 , where the volume changes, (positive above and negative below the OX axis) in cc. per IOO cc. of total constituent liquids, derived in an obvious way from the experimental data, are plotted as ordinates against the mixture-compositions as abscissae. The figures differ in that the composition
288
J . B. PEEL, W. M. MADGIN, AND H.
V. A. BRISCOE
is expressed in Fig. I as volume percentage and in Fig. 2 as gram-molecular percentage. It is noticeable] and may be significant] that the curves in Fig. I tend to be more symmetrical than those in Fig. 2.
TABLE I I
I1 (A
2
3 7 I1 25
24
8 4
5 6 12
26 9 21
I3 IO
I4 18 27
23
16 I9 20
28 22
I5
Acetone Ethyl acetate Hexane Ethyl alcohol Ethyl alcohol Hexane Aniline Ethyl alcohol Ethyl alcohol Aniline Hexane Methyl iodide Ethyl alcohol Benzene Ethyl acetate Chloroform Chloroform Ether Ether Ethyl alcohol Methyl alcohol Acetone Methyl acetate Ethyl acetate iso-Amyl acetate Acetone o-chloro phenol Ethyl alcohol
+
B
: carbon disulphide : carbon disulphide
E
+i.4 51.35
-9.75 -7.25
+0.9
-j.1j
B
+o.
-7.05
: acetone
: methyl acetate : ethyl oxalate : ethylene dibromide : carbon tetrachloride : ethyl acetate : carbon disulphide
25
0 0
C A
: o-dichlorobenzene
: carbon disulphide : ethylene dibromide : carbon tetrachloride
toluene methyl acetate ethylene dibromide methyl iodide carbon tetrachloride aniline : chloroform : chloroform : aniline : chloroform : chloroform : chloroform : chloroform : aniline : o-chlorophenol
V
IV
Volume Temperature change. change on Per cent for mixing IO cc A 50% (volume) I O cr: B* mixture*
+ B)
A I
I11
Pairs of liquida mixed
SO.
D G
-0.3 +o. IO
-6.85 -6.7 -j.8j -5.3
+o. 75 +0.4
-5.2
$0.3
-3.35
-5.05
-0.15
-1.1
-0. I
-0.4
$0. I
+.025
-0.3 j - .os
-0.3
+0,35
+
,025
-0.75
+1.45 +2.
75
I
