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Surface potential and surface tension of aqueous solutions of phenylarsonic acid and derivatives
Electrochimica Acta. 1965, Vol. 10. pp. 879 to 881.
Pergamon Press Ltd.
Printed in Northern Ireland
SURFACE POTENTIAL AND SURFACE TENSION OF AQUEOUS SOLUTIONS OF PHENYLARSONIC ACID AND DERIVATIVES* B. KAMIE~~SKI and E. KRAUSS Polish Academy of Sciences, Institute of Physical Chemistry, Physical Chemistry of Surface Phenomena, Krakow, Poland Abstract-Phenylarsonic acid changes the potential at the free surface of 0.1 M KC1 from -23 to -275 mV and the surface tension from 72.3 to 67.7 dy/cm over the concentration range from 0.01 to 0.1 M. o-and p-methyl derivatives of this acid are far more active; they decrease the potential to about - 600 mV at 0.06 M. The influence of pH on the surface potential and the surface tension was also measured; phenylarsenic acid and its derivatives are strongly surface-active in acid media. The inflexion points of the curves indicate that the dissociation constants are approximately lo+. R&urn&-Dans l’intervalle de concentration O.Ol-0,l M, l’acide phtnyl-arsonique modifie le potentiel g la surface libre de KC1 0,l M de 23 g 257 mV et la tension superficielle de 72,3 B 67,7 dy/cm-‘. Ses d&iv& mkthyliques o et p sont beaucoup plus actifs : ils abaissent le potentiel B environ 600 mV pour 0,06 M. L’influence du PH a Bt&aussi BtudiBe: l’acide et ses d&iv& sont surfactants Bnergiques en milieu acide. Les points d’inflexion des courbes obtenues impliquent des constantes de dissociation de l’ordre de lOma. Zusammenfassung-Phenylarsinsiiure verschiebt im Konzentrationsbereich von 0,Ol bis 0,l M das Potential der freien Oberfllche einer 0,l M KCl-LGsung von 23 auf 275 mV und die OberflLhenspannung von 72,3 auf 67,7 dyn/cm. Die o- und p-Methylderivate sind weit aktiver, sie verschieben das Potential bei 0,06 M auf 600 mV. Der Einfluss des pH auf das Oberfllchenpotential und die Oberfltichenspannung wurde ebenfalls untersucht. Phenylarsinslure und ihre Derivate sind in saurem Medium stark oberfllchenaktiv. Aus den Inflexionspunkten der Kurven ergibt sich eine Dissoziationskonstante von ungefghr lo-“. PHENYLARSONIC acid and its ortho and paru methyl-derivatives are much more soluble than benzoic acid and their dissociation constant are higher. However, according to Pressman and Brown,l similar substituted arsenic and benzoic acids have similar dissociation constants; those of p-phenylarsonic acid and benzoic acid change similarly when similar groups are introduced into the molecules, as found by Breyer.2 Benzoic acid3 and many its derivatives4 strongly influence the potential of the The potential and the surface-tension solution/air interface and the surface tension. changes of phenylarsonic acid solutions and its ortho and para methyl-derivatives in 0.1 N KC1 have now been measured by the dynamic jet method5 and the air-bubble method respectively, at 20°C. Acids are “classical” substances, decreasing both the potential and the surface tension.6 The changes of the electrocapillary properties were investigated as functions of the concerkrations of the compounds, and of pH between 2 and 10. Figure 1
* Presented at the 14th meeting of CITCE, November 1964. 879
Moscow,
August
1963: manuscript
received 7
B. KAMIE~SKI
880
and
E. KRAUSS
FIG. 1. Surface potential as a function of concentration. I, phenylarsonic acid, 2, its o&o-; 3, its para-methyl derivatives
shows the dependence of the surface potentials on the concentration of the compounds. Phenylarsonic acid changes the potential by -275 mV at concentration 0.1 M. Both its derivatives are far more active: the decrease of potential reaches -600 mV for the para isomer. Figure 2 shows that the surface tensions of the solutions of the three acids change linearly with respect to concentration within the measured range of the concentration.
FIG.
2. Surface tension as a funct.ion of concentration. acid; 2, its ortho-; 3, its para-methyl derivatives.
I, phenylarsonic
Figures 3 and 4 show the dependence of surface activity of the acids on pH. Whereas the influence of phenylarsonic acid and its derivatives on the surface potential and the surface tension is strong in acid media, the molecules ionize at higher pH and since ions avoid the surface, the surface activity diminishes as pH increases. The inflexion points of the curves (Figs. 3 and 4) indicate that the dissociation constants are approximately 1O-4 for the three acids investigated. The dissociation
Surface potential and surface tension of aqueous solutions of phenylarsonic
FIG. 3. Surface potential as a function of pH. 1, 0.04 M phenylarsonic acid; 2, 0.02 M o-methylphenylarsonic p-methylphenylarsonic acid.
I
731.5
I 5
I
8
acid;
acids
881
3, 0.04 M
DH
FIG. 4. Surface tension as a function of PH.
I, 0.04 M phenylarsonic acid; 2,0.02 M o-methylphenylarsonic phenylarsonic
acid; 3, 004 M p-methyl-
acid.
constants found earlier are : phenylarsonic acid, B 2.6 x acid,l 1.5 x 10e4, and for the para isomer, 2 I.7 x 10-4; agree reasonably. The above constants are considerably acid; nevertheless, when the molecules of the acids are pH 2-3, they influence the surface potential and surface
lo-“, o-methylphenylarsonic the results of both methods higher than that of benzoic un-ionized, in the region of tension remarkably strongly.
REFERENCES
1. D. PRESSMAN and D. H. BROWN, J. Amer. Chem. Sot. 65, 540 (1943). 2. B. BREYER, Ber. 71, 163 (1938). 3. A. FRUMKIN, A. DONDE and R. KULVARSKAYA, Z. phys. Chem. 123,321 (1926). 4. B. KAMIE~~SKI,Bull. Acad. Pal. Sci. Se’r. Sci. Chim. 8, 165 (1960); B. KAMIEIQSKI and M. PALUCH ihid. 8, 383, 683 (1960); M. PALUCH, ibid. 11, 97 (1963). 5. B. KAMIE~SKI, Bull. Intern. Acad. Polon. d. Sci., St+. A. Sci. Math. 129 (1935). 6. B. KAMIEI;ISKIWiadomosci Chem. 14, 619 (1960).
Pergamon Press Ltd.
Printed in Northern Ireland
SURFACE POTENTIAL AND SURFACE TENSION OF AQUEOUS SOLUTIONS OF PHENYLARSONIC ACID AND DERIVATIVES* B. KAMIE~~SKI and E. KRAUSS Polish Academy of Sciences, Institute of Physical Chemistry, Physical Chemistry of Surface Phenomena, Krakow, Poland Abstract-Phenylarsonic acid changes the potential at the free surface of 0.1 M KC1 from -23 to -275 mV and the surface tension from 72.3 to 67.7 dy/cm over the concentration range from 0.01 to 0.1 M. o-and p-methyl derivatives of this acid are far more active; they decrease the potential to about - 600 mV at 0.06 M. The influence of pH on the surface potential and the surface tension was also measured; phenylarsenic acid and its derivatives are strongly surface-active in acid media. The inflexion points of the curves indicate that the dissociation constants are approximately lo+. R&urn&-Dans l’intervalle de concentration O.Ol-0,l M, l’acide phtnyl-arsonique modifie le potentiel g la surface libre de KC1 0,l M de 23 g 257 mV et la tension superficielle de 72,3 B 67,7 dy/cm-‘. Ses d&iv& mkthyliques o et p sont beaucoup plus actifs : ils abaissent le potentiel B environ 600 mV pour 0,06 M. L’influence du PH a Bt&aussi BtudiBe: l’acide et ses d&iv& sont surfactants Bnergiques en milieu acide. Les points d’inflexion des courbes obtenues impliquent des constantes de dissociation de l’ordre de lOma. Zusammenfassung-Phenylarsinsiiure verschiebt im Konzentrationsbereich von 0,Ol bis 0,l M das Potential der freien Oberfllche einer 0,l M KCl-LGsung von 23 auf 275 mV und die OberflLhenspannung von 72,3 auf 67,7 dyn/cm. Die o- und p-Methylderivate sind weit aktiver, sie verschieben das Potential bei 0,06 M auf 600 mV. Der Einfluss des pH auf das Oberfllchenpotential und die Oberfltichenspannung wurde ebenfalls untersucht. Phenylarsinslure und ihre Derivate sind in saurem Medium stark oberfllchenaktiv. Aus den Inflexionspunkten der Kurven ergibt sich eine Dissoziationskonstante von ungefghr lo-“. PHENYLARSONIC acid and its ortho and paru methyl-derivatives are much more soluble than benzoic acid and their dissociation constant are higher. However, according to Pressman and Brown,l similar substituted arsenic and benzoic acids have similar dissociation constants; those of p-phenylarsonic acid and benzoic acid change similarly when similar groups are introduced into the molecules, as found by Breyer.2 Benzoic acid3 and many its derivatives4 strongly influence the potential of the The potential and the surface-tension solution/air interface and the surface tension. changes of phenylarsonic acid solutions and its ortho and para methyl-derivatives in 0.1 N KC1 have now been measured by the dynamic jet method5 and the air-bubble method respectively, at 20°C. Acids are “classical” substances, decreasing both the potential and the surface tension.6 The changes of the electrocapillary properties were investigated as functions of the concerkrations of the compounds, and of pH between 2 and 10. Figure 1
* Presented at the 14th meeting of CITCE, November 1964. 879
Moscow,
August
1963: manuscript
received 7
B. KAMIE~SKI
880
and
E. KRAUSS
FIG. 1. Surface potential as a function of concentration. I, phenylarsonic acid, 2, its o&o-; 3, its para-methyl derivatives
shows the dependence of the surface potentials on the concentration of the compounds. Phenylarsonic acid changes the potential by -275 mV at concentration 0.1 M. Both its derivatives are far more active: the decrease of potential reaches -600 mV for the para isomer. Figure 2 shows that the surface tensions of the solutions of the three acids change linearly with respect to concentration within the measured range of the concentration.
FIG.
2. Surface tension as a funct.ion of concentration. acid; 2, its ortho-; 3, its para-methyl derivatives.
I, phenylarsonic
Figures 3 and 4 show the dependence of surface activity of the acids on pH. Whereas the influence of phenylarsonic acid and its derivatives on the surface potential and the surface tension is strong in acid media, the molecules ionize at higher pH and since ions avoid the surface, the surface activity diminishes as pH increases. The inflexion points of the curves (Figs. 3 and 4) indicate that the dissociation constants are approximately 1O-4 for the three acids investigated. The dissociation
Surface potential and surface tension of aqueous solutions of phenylarsonic
FIG. 3. Surface potential as a function of pH. 1, 0.04 M phenylarsonic acid; 2, 0.02 M o-methylphenylarsonic p-methylphenylarsonic acid.
I
731.5
I 5
I
8
acid;
acids
881
3, 0.04 M
DH
FIG. 4. Surface tension as a function of PH.
I, 0.04 M phenylarsonic acid; 2,0.02 M o-methylphenylarsonic phenylarsonic
acid; 3, 004 M p-methyl-
acid.
constants found earlier are : phenylarsonic acid, B 2.6 x acid,l 1.5 x 10e4, and for the para isomer, 2 I.7 x 10-4; agree reasonably. The above constants are considerably acid; nevertheless, when the molecules of the acids are pH 2-3, they influence the surface potential and surface
lo-“, o-methylphenylarsonic the results of both methods higher than that of benzoic un-ionized, in the region of tension remarkably strongly.
REFERENCES
1. D. PRESSMAN and D. H. BROWN, J. Amer. Chem. Sot. 65, 540 (1943). 2. B. BREYER, Ber. 71, 163 (1938). 3. A. FRUMKIN, A. DONDE and R. KULVARSKAYA, Z. phys. Chem. 123,321 (1926). 4. B. KAMIE~~SKI,Bull. Acad. Pal. Sci. Se’r. Sci. Chim. 8, 165 (1960); B. KAMIEIQSKI and M. PALUCH ihid. 8, 383, 683 (1960); M. PALUCH, ibid. 11, 97 (1963). 5. B. KAMIE~SKI, Bull. Intern. Acad. Polon. d. Sci., St+. A. Sci. Math. 129 (1935). 6. B. KAMIEI;ISKIWiadomosci Chem. 14, 619 (1960).