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J. C h m . Eng. Data 1995,40, 611-814
+
Surface Tension of N~ohCd Water from 20 to 50
Gonzala vhzquez,* Estreua Alvarea, and
M- J?hvaza
Depdmentof chemicalEngineeriag, U d v e r s i v of Santiago de C~mpogtela,
measured
The surface tension of aqueous solutions of methanol, ethanol, I-propanol, and 2-propmol
over the entire concenkation range at temperatures of 20-50 "C. The experimental values were camdated
with temperature and with mole frattion. The maximum deviation was in both cases alwaya leas than
3%.
+
Table 3. Surface Tamian of 1-Propano1(11 Water (21
Introduction
The surface tension of mixtures is a physicat propem
of great importance for mass transfer processes such as
distillation, extraction, or absorption. h relation to our
regearch (Vazquez et al., 1990) on how mass transfer is
inQuencedby the Marangani effect (apontaneaus interfacial
turbulence generated by surface teneion gradients), in this
work we measured the surface tenaion of methanol
water, ethanol + water, 1-propanol + w a t ~ and,
~ , 2-propan01 f water over the entire concentration range at
temperatures of 20-50 "C.
.,
+
,
. .
'
Experimental Section
. ,
Aqueous solutions of methanol, ethanol, 1-propanol. m d
2-pmpanol were prepared with distilled, deionized water.
The alcohoIs were Merck products of nominal purity
,99.7%. All the solutions were prepared by weight with
Table 4. durface Tension of 2-F%opmol'(l)4- Water (2)
u/tmNpl-=)at tPC
Water (2)
'Fable 1, Slurface Tension of Methanol (1) i-
0
5
10
15
20
25
90
40
50
60
70
80
90
100
0.006
0.029
0.059
0.090
0.123
0.158
0.134
0.273
72.75 72.01 71.21 70.42 69.52
63.46 62.77 61.90 61-14 80.32
56.87 56.18 55.41 64.87 54.01
51.83 51.17 60.43 49-76 47.04
47.86
44.38
41.67
37.02
0.360 33.37
0.458 30.32
0.568 27.91
0.692 25.98
0-835 24.37
1.000 22.95
47.21
49.78
41.09
36.61
32.86
29.83
46.66
49.14
40.43
35.90
32.33
45.84
42.51
39.77
35.36
31.85
29.34 28.86
27.48 26.89 26.66
25.54 25.06 24.60
23-98 28.43 22.95
22-61 22.01 21.52
68.04 67.92
59.58 58.77
53.27 52.46
40.39 47.62
45.17 44.49 48.76
41.82 41.21 40-67
39.14 38.53 37.88
34.79 84-18 33.62
31.26 30.77 30.28
28.44 27.93 2.7.54
26.12 25.84 25.23
24.21 23.72 23.33
22.57 22.06 21.67
21.13 20.61 20.21
I-.
Table 2. Sutface Tenpion of Ethlano1 [l)t Water (2)
mass %
deviations of lem than 0.3% from the desired concentratione, which are indicated in Tables 1-4 as mole &action.
Surface tension w~ determined at 5 'C intends between 20 and 50 "C,using a Pmlabo tensiometer, which
employs the Wilhelmy plate p ~ n c i p hILin et al., 1990;
Bogaert et d.,19801,thermostated with a prrxision of hO.1
'C. Values shown beIow are averagas af 5-10 measure
ments; maximum deviations &om the average wera dways
Ieas than 0.4%.
Results and Discussion
- ~ablek1-4 Iist t h a measured surface tensions of methanol water, ethanol water, 1-propanal water, snd
2-propanol f water of v a t i o u e concentrations a t each
temperature. In aU the systems studied aurface tension,
u, decreased with increasing temparatue for any given
mole fraction of Jcohol. The surface tensions o f the pure
components can be correlated with tomperature by fitting
+
+
0021-9568/95/1740-0611$09.00/06 1995 American Chemical Society
+
07/30/98
15:40 FAX
618 Journal of Chemical and Engineering Data, Val. PO, No. 3,1995
.,
F'igure 1. Surface tension as a functioh of tamperature: U, water;
0.5 mass % ethanol; H, 10 mass Q ethanol; 0 , 2 0 maem C ethanol;
A, 50 mass % ethanol; V, 80 mass 5% ethanol:
100 mass 46
ethanol; -, e q 1.
Figare 9. Fitted parameter a (eq 2) as a function of tamperature: I,methanol; A, ethanol; a, 1-pmpanol; r,2-propanal.
Fig
the
2:
Tab
A
s'01'
tor.'
ma
etl
I-:
2-rr
Figure 2. Dhe~sionlesasurface ternion fl plothd against the
mole fraction of alcohol: 0,methaa0120 'C; methanol, 56 'C;
H, &-I,
26 ' C ; 0,e-01,
50 "C;v,1-propanal, 20 "C; A,
l-vpEUl~l,60 'C; 0,2-pr0p~n01,20 OC; V, 2-pmp~II01,50 'C.
.'
the following linear expression (Jasper, 1972):
+,
Equation 1 also fitted the data of Tables 1-4 for each
concentration, with deviations of less than 1%. Fimre 1
.,
Figure 4. Fitted parameter b (eq 2) ae a function of temperature: methanol: A. ethanol; 1-pmpanol; V, 2-prop-1.
+
tii
shows the resultn for ethanol water aa an example. 'I'he
fitted values pf Kland K2are listed in Table 5.
For a given temperature, the surface tension o f mixtures
studied in this paper decreased as the alcohol concentration
increased. This trend was nonlinew, the change in ~urTace
tension caused by a given chnnga in alcohol concentration
being larger at low concentrations than at high concentra-
to
tc.
x1
yi
15:41 FAX
07/30/98
Journal of 1Themkal and Engimering Llata, VoI.40, hT6.3,1995 613
1s
o
+
Figure 5. Surface eneion of methanol water plotted against
tho mole fraction of methand: U, exptl, 20 "C;-, calcd. 20 'C; A,
exptl, 30 'C; ---,
30 -C;v, q t l , 40 'C; - -,d e d , QO ' C ; 0 , exptl.
60 'C; -, calcd, 50 OC.
-
.
I
L.
02
074
.
I
I
n,~
-,. .-.- . . - .--- - , .
Xl
z
.
IP-
.
-
Fi-
6. SzLrface tendon of 2-propano1+water agahut the mole
fraction of2-propam11I ,Hoke et d,,
1991,25 ' C ; A, Hoke et al-,
1991,40 T;
V,Hoke et al., 1991,50OC;0,
Cheong a t P.,1987,25
'C; -, eq 2,25 "C; ---,
eq 2,40 'C;
eq 2. 50 "C.
---.
Table 5. HurEace Teseion Parameters Klasd KXfor
Aqueous 0tganic Mixtures
or~anic
component
z1
E
l
KQ
xi
KI
E g
methmol
0.000
0.029
0.059
0.090
0.128
0.158
0.194
ethanol
0.000
0.020
0.042
0.065
0.039
0.115
0.114
1-propanal 0.000
0.018
0.082
0.060
0.0M
0.091
0.114
2-propanal 0.000
0.016
0.092
0.050
I
0
0.070
0.091
0.114
_
I
I
1
034
Q,6
0,s
1
xi
tiosa. Fitting the squation
C
tb the data for snch solute (where uwand u., are the surface
tenaions of pure water and pure alcoh01, respectively, and
xl and x i are the mole fractions of dcohol and water)
yielded LP $1 curves like those shown in Figure 2 for
-
0,2
Figure 7. Excesa surface tension r 9 u lrr function o f the mole
&action of alcohol: 0,methanol, 20 'C; +, methanol, 50 'C; A,
ethanol. 20 "C; m, ethanol, 50 "C; 0, 1-propanol, 20 "C; 7 ,
1-propand, 50 'C; - d d d from eqa 2 and 3.
temperatures of 20 and 50 'C. The dimensionless surface
termion d can be considered aa independent of temperature
over mast of the concentration range. T h e values of the
fitted parametere a and b in eq 2 are linear fuhctions of
temperature for each alcohol {see Figures 3 and 4)- Figure
15:41 FAX
614 Journal of Chemical and Engineering Data, Vul.40, No. 3,1995
07/30/98
5 ahowa, by way of example, the memured surface tensiona
of methanol water in comparison with those calculated
by means of eq 2. The deviation8 are lese than 3% in all
+
such plots.
Experimental valuea obtained by other researchers cannot be directly compared with the values reported in this
paper because of differences in the concentrations used.
They can, however, be compared with values predicted by
eq 2. In the previous reports considered (for methanol +
water at 25 'C (Cheong and Cam, 18871,ethanol water
at 25 "C(Ernst et al., 19361,l-prbpanol+ water at 20,30,
40, and 50 "C (Martin et al.,19831,and 2-propanol water
at 26 "C (Cheong and Cam, 1987; Hoke et al., 1991)and at
30,40, and 50 "C (Hoke s t al., 199111, 92% of the values
deviate by Ieaa than 6% &om the predictions of eq 2. The
remilts far 2-propano1 + water a& shown as an &ample
id Figure 6.
The sensitivity of the surface tension of thesa systems
to the chmges in concentration in the low alcohol concentration region reflects the nonideal character o f these
mixtures. The deviation from ideal behavior can be
q u a n a e d by the exceee surface tension as,de6ned by
+
+
Plotting UE against the male haction of organic component (Figure 7 shows typical plots) ~ h o w sthat deviation
*om ideality increases with the length of the organic
molecula and decreases with rising temperature:
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W. J,; C m , P. W. The Surface Teasion of e u r c s of
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Emmt, R C.;Watkins, C. H.; Ruws. H. H. The Physical Properties of
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MarMn, A.; FbseUb, A: Rodriguez.J. M.; Hormigo, 4 EstEmatioa of
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issa,~ s s , ~ w - ~ s a .
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Chon
b w h d for d
w September 23, 1994- hcepted Jannarp 10,
1995.9 This work w* p a r t i d y h a n c c ? L;Y--C-'- E*l$A*
(Spain) (Grant KLTGA 20909 B94).
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Ir
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