Wetting and Spreading Properties
of Aqueous Solutions
APPLYINGOIL-EMULSION SPRAYWITH
A
POWBRSPRAYER
PREVIOUS paper of this series (1) showed that the wetting properties of aqueous sodium hydroxide-oleic acid mixtures are dependent upon the alkali-fatty acid ratio, and that at moderately high concentrations the wetting properties are adversely affected by even a slight excess of the alkali. It has also been shown (a) that the wetting properties of aqueous sodium carbonateoleic acid mixtures are much less dependent upon the alkali-fatty acid ratio than are the corresponding mixtures in which sodium hydroxide is used as the base. Since the hydroxide is a stronger base thannthe carbonate, an excess of the hydroxide will increase the concentration of hydroxyl ions to z1 greater extent than will an excess of the carbonate. Therefore, an excess of the hydroxide might be expected to produce the greater change in the degree of hydrolysis of sodium oleate solutions and consequently have the greater effect upon the surface properties of the mixtures, as has been found in the experimental measurements of surface and interfacial tensions. I n the present paper the study has been extended to include mixtures of oleic acid with three additional inorganic bases-potassium hydroxide, potassium carbonate, and ammonia.
Experimental Procedure FIGURE 1. VARIATION IN WETTING PROPERTIES WITH ALKALIFATTY ACID RATIOFOR POTASSIUM HYDROXIDE-OLEIC ACID MIXTURES 434
The spreading co$fficient, S , of a soap solution over the standard mineral oil is defined by the following equation:
Mixtures of Oleic Acid with
Potassium Hydroxide, Potassium Carbonate, and Ammonia H. L. CUPPLES Bureau of Entomology and Plant Quarantine, U. S. Department of Agriculture, Washington, D. C.
where
Tg =
TA= TAB =
S = TB - T A - TAB surface tension of oil (30.5dynes/cm. at 25" C.) surface tension of soap solution interfacial tension
The experimental procedure in these experiments was the same as previously described ( I , 9).
Discussion of Results Table I and Figure 1 show how the wetting properties vary with the alkali-fatty acid ratio for solutions containing 1.00, 0.30, and 0.10 gram of oleic acid per 100 cc., with potassium hydroxide as the alkali. Table I and Figure 2 show ,similar data for mixtures containing potassium carbonate as the alkali. In all of the figures presented here, shaded areas indicate positive spreading coefficients, the reference liquid is mineral oil, and the temperature is 25' C. Table I1 and Figure 3 present data for ammonia-oleic acid mixtures containing 1.CO gram of oleic acid per 100 cc. Since these mixtures lose ammonia upon exposure to the air, thus making the accuracy of the results somewhat uncertain, other concentrations were not studied. It was observed that the mixtures containing 0.8 and 1.0 mole of ammonia Der mole of oleic acid did ;lot spread over a film of oil on celluloid. This behavior may have been due to loss of amSurface tensions, intermonia from the soap mixture facial tensions, and spreadupon exposure to the air in ing coefficients on a refined a thin film. The other mixparaffin oil were determined tures, containing more ammonia, did spread over the for a series of potassium hyoil. droxide-oleic acid mixtures, Potassium hydroxiddeic potassium carbonate-oleic acid mixtures were found to acid mixtures, and ammobe similar to the correspondnia-oleic acid mixtures. The ing sodium hydroxide-oleic acid mixtures. That is, the behavior of the potassium wetting properties are decompounds is similar to that p e n d e n t up:on the akaliof the corresponding sodium f a t t y a c i d r a t i o , and a compounds. Only the mixslight excess of alkali may ~~
tures containing sodium or potassium hydro xi de are highly sensitive to a variation of the alkali-fatty acid ratio.
FIGURE2. V A R I A T I O NI N W E TT I N Q PROPERTIES WITH ALKALI-FATTYA c I D R A TI o FOR POTASSIUM CARBONATEOLEICACID MIXTURES 435
INDUSTRIAL AND EIL'GINEERING CHEMISTRY
436
VOL. 28, NO. 4
TABLE I. VARIATION IN WETTINGPROPERTIES WITH ALKALI-FATTY ACID RATIOAT 25" C. Interfacial Tension against Oil
KOH/ Oleic -4cid Moles
Surface Tension
0.80 0.90 1.00 1.10 1.25 1.50 1.75 2.00 3.00 4.00
25.3 25.2 26.7 29.4 32.3 32.7 32.7 32.8 31.7 30.8
0.8 0.8 1.7 4.3 5.3 5 5 5 4 5.3 3.8 3.4
0.80 0.90 1.00 1.10 1.25 1.50 1.75 2.00 3.00 4.00
25.1 25.1 25.0 26.0 28.9 31.9 32.4 33.0 33.3 33.0
1.5 1.6 1.8 2.7 4.4 5.5 5.8 5.9 5.6 5.5
0.80 0.90 1.00 1.10 1.25 1.,50 1.75 2.00 3.00 4 00
24.8 24.8 24.8 24.8 24.8 25.0 27.5 29.2 31.3 32.6
5.8 4.4 3.5 3.4 3.6 3.4 4.1 4.9 5.3 5.4
Dunes per cm.
Spreading Coefficient on Oil
K2COd Oleic Acid Moles 1.00 Gram Oleic Acid per 100 Cc. +4.4 +4.5 +3.1 -3.2 -7.1 -7.7 -7.6 -7.6 -5 0 -3.7
0.80 0.90 1.00 1.10 1.25 1.50 1.75 2.00 3.00 4.00
0 . 3 0 Gram Oleio Acid per 100 Cc. +3.9 0.80 +3.8 0.90 $3.7 1.00 +1.8 1.10 -2.8 1.25 -6.9 1.50 -7.7 1.75 -8.4 2.00 -8.4 3.00 -8.0 4.00 0.10 Gram Oleic Acid per 100 Cc. -0.1 0.80 +1.3 0.90 1.00 +2.2 +2.3 1.10 +2.1 1.25 +2.1 1.50 -1.1 1.75 -3.6 2.00 -6.1 3.00 -7.5 4.00
greatly change these properties. Also, the potassium carbonate-oleic acid mixtures were found to resemble closely the corresponding sodium carbonate-oleic acid mixtures; the carbonate mixtures are much less sensitive to variation of the alkali-fatty acid ratio. The ammonia-oleic acid mixtures are also relatively insensitive to an excess of the base. These results indicate that the remarkable sensitiveness of the hydroxide-oleic acid mixtures to an excess of the alkali is due primarily to the action of the hydroxyl ion rather than
Interfaci a1 Tension against Oil
Surface Tension
Spreading Coefficient on Oil
D y n e s per cm. 25.7 25.6 25.6 25.4 25.8 26.8 27.5 27.8 28.8 29.2
0.8 0.6 0.3 0.3 0.6 0.6 0.8 1.0 1.4 1.4
4-4.0 +4.3 +4.6, +4.8 +4.1 +3.1 +2.2 +1.7 +0.3 -0.1
25.4 25.4 25.4 25.3 25.1 26.1 27.3 28.2 29.4 29.7
4.0
+l.l
1.6 1.8 1.5 1.4 1.8 2.1 2.8 2.8
25.1 25.3 25.1 25.2 25.2 25.2 25.2 25.4 27.6 29.2
10.9 10.0 9.6 9.7 5.6 3.1 2.2 1.8 1.9 3.4
1.9
+3.2 +3.5 +3.4 +3.9 t-3.0~ +1.4 +0.2 -1.7 -2.0 -5.6 -4.9. -4.2 -4.4 -0.3 +2.a +3.1 +3.3 +1.0 -2.1
of the sodium or potassium ion. This furnishes a possible explanation for the beneficial action of certain adjutants used' in washing compounds, such as the silicates and phosphates. The stabilizing effect of these compounds on the hydroxyl-ion concentration may be responsible, a t least in part, for their effectiveness. TABLE 11. VARIATIONIN WETTINGPROPERTIES WITH AMMONIAOLEIC ACID RATIOFOR MIXTURESCONTAINING 1.0 GRAMOLEIC ACID PER 100 Cc. AT 25" C. "3',
Oleic .4cid Moles 0.8 1.0 1.5 2.0 3.0 4.0
Surface Tension I
25.2 25.2 25.6 25.8 26.1 26.2
Interfacial Tension against Oil Dunes per cm. 2.4 2.0 1.0 0.5 0.4 0.4
S reading &efficient on Oil +2.9 +3.3 +3.9 +4.2 +4.0 f3.9
Literature Cited (1) Cupples, H.L.,IND.ENQ.CHEM.,27,1219 (1936). (2) Ibid., 28, 60 (1936). RECEIVED October 24. 1935.
r
WITH ALKALIFIGURE 3. VARIATIONIN WETTINGPROPERTIES FATTY ACID RATIOFOR AMMONIA-OLEICACID MIXTURES
Nothing is more certain than the assurance that this Century's marvelous scientific discoveries are onIy hints of the extraordinary secrets Nature has yet to reveal to adequate research, and nothing is more obvious than that our use and application of these discoveries for human welfare must be widely ex-tended before we can even feel satisfaction.
WILLLAM. S. PALEY
