Surface Tension of Ethyl AlcoholWater Mixtures W. S. BONNELL, L. BYMAN,
AND
The surface tensions of eight ethyl alcoholwater mixtures (from 2.33 to 92.72 per cent ethyl alcohol by weight) were determined at temperatures ranging from room temperature to the atmospheric boiling points of the various solutions. The surface tension decreased slowly with increase of temperature in linear relationship. At constant temperature the surface tension was found to decrease with increased concentration of alcohol, rapidly at first (up to 20-30 per cent by weight) and then more slowly.
D. B. KEYES
University of Illinois, Urbana, 111.
HE surface tension of the liquid in a fractionating column is thought to be one of the important factors which control the plate efficiency (6). In order to evaluate this factor practically, the surface tensions of ethyl alcohol-water mixtures have been determined a t temperatures below and a t their atmospheric boiling points. The capillary rise method was used because it was simple and was most convenient for determining the change in surface tension of a mixture over a temperature range. The capillary rise was ascertained by measuring, with a cathetometer, the difference in height of the liquid in the two arms of a U-tube, made (with minor changes) according to a design suggested by Young (12). The radius of the larger arm, as determined by Noyes and Singh (9), was 0.22312 cm.; the radius of the smaller arm was determined from measurements of the capillary rise of water in the apparatus. The surface tension was calculated by a formula recommended by Young:
T
Y =
where
y = h =
D = d = r., T = g =
rc r (3h
measured with a hydrometer which was placed in a closed glass cylinder containing approximately 150 ml. of the mixture. The reason for using a cylinder which could be closed to the atmosphere was to prevent changes in composition of the mixture due to vaporization. The true density of the mixture was obtained by multiplying the hydrometer reading by a correction factor which was equal to the ratio of the density of water (IO) to the - \ hydrometer reading for distilled water. The values, incorporated in the correction factor, FI LLI NG were for the same L TUBEtemperature as that a t which the c) density of the mixture was being dec'9 -0 termined. The surface tension apparatus was RADIUS cleaned by filling 0.22312 CM. it with cleaning (MEASURED) solution (sodium dichromate and sulfuric acid). The 7 cleaning solution W was washed out 4NO ETER with tap water, I and the apparatus was rinsed several APILLARY RADIUS times with distilled 0.03296 CM. water and then (CALIBRATED) twice with acetone. Air was passed through until the FIGURE 1. SURFACE TmsIoPr apparatus was dry. APPARATUS
+ re - r ) (D - d)g 6(r -
t
Tc)
surface tension difference in height (capillary rise) density of liquid at temperature of measurement density of vapor above liquid two radii local gravitational acceleration = 980.14 cm./sec.*
In the calculation of the surface tension of the ethyl alcoholwater mixtures, the term d in the formula was ignored b e cause the error thus introduced was considerably smaller than the experimental error of the work.
Experimental
is
The apparatus (Figure l), made of Pyrex glass, was suspended in a glycerol-filled Leita battery jar to facilitate measurements over a temperature range. The jar was of plate glass and did not give any apparent optical distortion. A sheet of frosted glass was placed against the back of the bath and a lamp behind it, in order to provide a good optical background. Heating and cooling coils were used to vary the temperature, and a stirrer of variable speed maintained the same temperature throughout the bath. A leveling mark was scratched on the capillary tube in order to nullify the effect of any irregularities in the bore on the reproducibility of the experimental results. The experimental procedure was as follows: The solutions to be measured were prepared by mixing the required amounts of distilled water and 95 per cent ethyl alcohol necessary to give the desired concentration. The alcohol was tested qualitatively for impurities according to the method outlined by Murray (8). None were detected. The exact composition of the mixtures was determined by means of pycnometric measurements of their densities. The density of the mixtures a t the various temperatures was 532
APRIL, 1940
INDUSTRIAL AND ENGINEERING CHEMISTRY TABLE11. ETHYLALCOHOL-WATER MIXTURES
TABLEI. COXDCCTIVITY WATER" D(f0) G./ml.
Temp. ' C. 20.0 30.0 40.0 .50.0 60 0 70 0 80.0 90.0
d G./cc.
hsv.
.....
..... 0,00112 0,00108 0.00103 0,00098 0.00093
3:82 3.79 3.71 3.62 3.52
.....
.....
..
.
..
I
.....
(4)
rc
Cm. Dynes/cm.
0,99568 0,99224 0.98807 0.98324 0.97781 .
Y
72.75 71.18 69.56 67.91 66.18 64.42 62.61 60.75 Average
,,
Cm.
-; b
Temp.
Dynes/cm.
...... 0,03313 0.03275 0,03281 0.03208 0.03318
., ., .. ......
533
7018 70.0 68.2 66.2 64.0
..
C.
Barometric pressure. 747 mm. Hg; relative humidity, 38 per cent. I The average i-c was used in calculating the values of surface tension given under y in this and the following tables.
The manometer attachment was filled with mercury to the proper level. A piece of rubber tubing was placed on the open end of the manometer and clamped. A rough estimate of the pressure in the system could be obtained by approximating the decrease in volume of the air above the mercury and by measuring the difference in the height of mercury in the two tubes of the manometer. (The U-tube used as a manometer was employed only as an overflow and drainage arm in the original apparatus, which was designed for measurements of higher precision a t room temperatures.) The surface tension apparatus was filled with the liquid to be measured to a point several centimeters above the scratch on the capillary tube (T = 0.03296 cm., calculated from the data on water). A drawn capillary tube (cleaned by the same method as the apparatus) was inserted into the filling arm, and liquid was withdrawn until the liquid in the capillary
hav.
Y
Cm.
Dynes/ cm.
D
hsv.
Y
G./ml.
Cm.
Dyneal cm.
Temp. C.
43.64 Weight 28.1 0.9160 39.7 0,9114 0,8986 55.6 0.8860 70.9 0,8767 81.5
% Alcohol
5 . 9 4 Weight % .. Alcohol 54.1 0.9862 2.96 0,9821 52.0 2.86 50.1 0,9732 2.78 0,9635 2.66 47.4
61.10 Weight 0.8848 25.8 39.2 0.8744 0,8599 54.0 0,8437 69.7 81.3 0.8346
yo P_. l r-n- h o. l.
15.93 Weight % Alcohol 24.3 0.9727 2.33 41.8 39.6 0.9664 2.25 40.0 54.8 0.9576 2.16 38.0 70.1 0.9474 2.05 35.7 88.6 0.9324 1.94 33.2
73 . 6 8 Weight 20.1 0.8519 0,8484 26.8 40.4 0.8345 0,8246 51.2 0,8125 62.t 0.8047 72.5 0,7970 81.2
% Alcohol
29 ,157 Weight % Alcohol 0,9493 i.90 33.0 25.8 42.4 0,9473 1.85 32.1 54.4 0,9298 1.82 31.0 69.5 0,9174 1.77 29.7 86.2 0.9045 1.73 28.6
' Alcohol 92. 72 Weight % 1.56 22.9 0.8064 25.5 1.52 22.0 0.7966 38.5 1.48 21.0 0.7824 49.2 1.48 20.4 0.7759 58.5 1.42 19.7 69.0 0.7653 1.40 19.2 78.7 0.7563
30.0 44.6 59.2 73.7 88.9
2 . 3 3 Weight 0.9914 0,9872 0.9792 0,9702 0,9614
24.7 40.6 59.1 74.5
0.032966
0
D G./m1.
% Alcohol 3.27 3.18 3.12 3.07 2.95
60.2 58.3 56.7 55.3 52.6
i
w
U
c
(r
3
In
20
I 10
I
I
I
I
I
I
I
TEMPERATURE IN DEGREES CENTIGRADE
FIGCRE2.
1.65 1.62 1.58 1.55 1:19 1.64 1.62 1.57 1.51 1.48 1.46 1.42
28.2 27., 26.8 25,s 25.0 26.0 25.8 24.7 23.8 22.6 25.4 25.0 23.8 22.6 21.8 21.3 20.5
tube was level with the scratch. The reason for this procedure was to wet the walls of the capillary and to permit the liquid in the capillary to stand a t its true height. The open ends of the apparatus were then closed by plugs.
00
WATER-
1.69 1.67 1.64 1.88 1.37
SURFACE TEXSIOX O F ETHYL -4LCOHOL--WATER ?VIIXTURES
I
INDUSTRIAL APiD ENGINEERING CHEMISTRY
534
TABLE 111. COMPARISON O F D.4T.4 WITH LITERATCRE (5)a Weight %Alcohol 2.33 5.94 15.93 29.67 43.64 61.10
7 1 5 ' C.-
-25'
( F i i . 2) 62.0
(Fi; 2) 60.8 54.0
VALCES
C.-
GIVENIN
7 - 3 0 ' C.-
(6)
THE
(x)
( F i l 2) 62.8 61.2 60.2 60.8 55.3 54.6 53.6 53.4 52.3 43.1 42.4 41.8 4 1 . 1 41.2 40.3 33.8 33.9 33.1 32.6 32.8 32.1 29.1 29.7 28.5 2 8 . 8 2 8 . 2 28.2 27.4 27.2 26.7 26.3 2 6 . 3 26.0 75.68 25.8 25.6 25.0 24.9 24.6 24.7 92.72 23.6 24.2 22.9 23.3 2 2 . 5 22.5 a The values under y ( 6 ) were taken (by graphical interpolation) from the data of the International Critical Tables, derived from the measurements of Traube (111, Bircumshaw ( I ) , and Morgan and Neidle ( 7 ) . ):(
A steel base was attached to the apparatus and a split rubber stopper was placed around the filling tube. The apparatus was supported in the bath by a clamp attached from the stopper to a ring stand and was checked m-ith a plumb line to make sure it was in a truly vertical position. The cylinder, containing the hydrometer and liquid mixture, was also placed in the bath and supported by a clamp attached t o the ring stand. The stirrer was started and the heating coil turned on. At intervals of approximately 15' C. the height of the capillary rise, the hydrometer reading, and the difference in height of the mercury levels were recorded. The temperature range covered was from room temperature to several degrees above the atmospheric boiling point.
VOL. 32, NO. 4
The height of the rise of the liquid in the capillary was measured with a cathetometer (by difference). Before each reading the cathetometer was leveled. Three or four readings w'ere taken, and the arithmetical average of the differences was considered the value of h (capillary rise). The difference in level of the mercury in the manometer was also determined with the cathetometer.
Acknowledgment The authors are indebted to T. *F.Young for his valuable suggestions during the course of this work. They also wish to thank W.&I.Langdon for the determination of the compositions of the mixtures studied.
Bibliography Bircumshaw, L. L., J . Chem. SOC.,121, 887 (1922). Firth, J. B., Ibid., 117, 268 (1920). Harkins, W. D., and Brown, F. E., J . Am. Chem. SOC.,41, 499 ( 1919). International Critical Tables, Vol. IV, p. 447, Kew York, McGraw-Hill Book Co., 1928. Ibid., Vol. IV, p. 467. Keyes, D. B., Univ. Illinois Eng. Expt. Sta., Circ. 35 (1938). Morgan, J. L. R., and Neidle, M., J. Am. Chem. SOC.,35, 1866 (1913). Murray, B. L., "Standards and Tests for Reagents and c. P . Chemicals", 2nd ed., New York, D. Van Nostrand Co., 1927. Noyes, W. A . , and Singh, B., J. A m . Chem. SOC.,58, 802 (1936) Perry, J. H., Chemical Engineers' Handbook, 18t ed., p. 377, New York, McGraw-Hill Book Co., 1934. Traube, J., J. prakl. Chem., 31, 177 (1885). Young, T. F., private communications.
Vapor-Phase Esterification of Benzoic Acid with Ethyl Alcohol J
E I D (18) has reviewed the recent work in the field of esterification. His survey cites the progress made in manufacture and indicates the need for research to find the proper catalyst for the reaction and to establish the optimum conditions for a given esterification. I n studying ester formation both in the liquid and vapor phase, the system ethyl alcohol-acetic acid has been most commonly used. Other aliphatic or aromatic systems have not been extensively investigated up to the present time. The formation of ethyl acetate from ethyl alcohol and acetic acid has been the subject of much research. Frolich, Carpenter, and Knox ( 8 ) and Edgar and Schuyler ( 6 ) used zirconium oxide as a catalyst; Mill'gan and Reid (16) and Reid (18) used silica gel; Sandor (20) investigated vanadium pentoxide, cobalt oxide, cesium oxide, and silica gel; Mailhe (16) compared thorium oxide, zirconium oxide, and titanium oxide; a patent (4) described the use of magnesium oxide and manganese dioxide. Dreyfus (6) described the use of alkali and alkali metal compounds as catalysts, and Winkler and Hinshelwood (21)used hydrogen chloride to catalyze the formation of ethyl acetate a t 450' C Esters of ethylene glycol and acetic acid in the vapor phase were prepared catalytically by Turova, Pollack, and Dzioma @ I ) , using activated carbon impregnated with phosphoric acid. Brown and Reid (2) passed vapors of ethyl and butyl
R
1
Present addrese, Northeastern University, Boston, Mass.
Effect of Oxides on Catalytic Activity of Silica Gel ARTHUR A. VERNON' AND BERTRA-M M. BROWN' Rhode Island State College, Kingston, R. I.
alcohols over tungstic oxide, alumina, thoria, and silica gel to prepare the respective esters. Lazier (11,13) described the production of several esters by passing alcohols over mixtures of various oxides. He used, among others, oxides of zinc, chromium, manganese, magnesium, cesium, vanadium, tungsten, uranium, copper, cadmium, and lead. Legg and Bogin (14) passed butyl alcohol over fused and crushed cupric oxide. Sabatier (19) showed that the reaction velocity for esterification was greater with aliphatic acids than with benzoic acid and its analogs in both the liquid and vapor state. Jaegar (9) claims reaction and formation of ethyl benzoate from benzoic acid and ethyl alcohol a t 200" to 350" C. when passed in the vapor phase over a mass containing a t least
