title pressure effect on conductance of aqueous solutions...

Title Pressure effect on conductance of aqueous solutions ofpotassium halides

Author(s) Shimizu, Kiyoshi; Tsuchihashi, Noriaki

Citation The Review of Physical Chemistry of Japan (1979), 49(1): 18-24

Issue Date 1979-07-25

URL http://hdl.handle.net/2433/47073

Right

Type Departmental Bulletin Paper

Textversion publisher

Kyoto University

The Review of Physical Chemistry of Japan Vol. 49 No. 1 (1979)

THE REVIEW OF PHYSICAL CHE3HSTRY OP JAPAK, VOL. }9, No. I 1979

PRESSURE EFFECT ON CONDUCTANCE OF AQUEOUS SOLUTIONS

OF POTASSIUM HALIDES

RY KIYOSHi $HI NIlU AND 1\~ORIAKi TsucH]HASHI

The ronductances of the aqueous solutions of potassium halides have heed measured at 15-•}0-C' up [01500kg/cmx." The limiting molar conductivities, A'(KX) were determined by the extrapolation to zero concentration in the Kohlrausch plots. There is good agreement between the present data of A'(KX) and tbose calculated with the empirical equations in pressure by Gancy and Brummer. The limiting ma]ar conductivities of The ions, K', CP, Br- and Y were calculated with the transport numbers of K* ion, respectively. The vari-ations of the conductivity ratio 2v /lf of each ion with pressure were charac-teristic and may he ascribed to the various effects induced by the ion, pressure and temperature on the three dimensional order of water. On the contrary to the received view, judging from these results, Ct-and Br-ions would apparent• ly behave like the structure maker, as F- ion, and R' and I- ions the structure breaker a[ atmospheric pressure.

Introduction

The most extensive measurements of the ronductances of the electrolytic solution at high press-

ures have been concerned with the aqueous solutions of KCI at 25°C. The limiting molar conductivity

of KCI, ~'(KCl) has been applied for the discussions of many problems such as pressure effects on

the mobility of K* and Cl' ions]-31, the excess mobility of H* and OH' ions;'%1, and the dissociation

of weak electrolytess-lot, Bu[, there is some discrepancy between several sets of published con-

ductance data which may be explained in terms of the cell materials, the concentration of solution

and the contamination from the pressure-transmitting fluid. For example, the data of Nakahara of alsl

show somewhat higher values of A' (KCI) in higher pressure region in comparison with the results of

(Received blank 24; 2979) + T/R-273.15+(!/'C) ss 1 kg/cmZ-9.80665 x lM Pa 1) S. B. Brummer and G. J• Hills, Trans. Faraday Soc., 57, 1816, 1823 (1961) 2) R. H. Horne, B. R. dyers and G. R. Frysiager, J. Chem. Pkys., 39, 2666 (1963) 3) ilf. Nakahara, R. Shimizu and J, Osugi, This lau.nal, 42, l2 (1972) 4) 5. D. Hamann and SV. Strauss, Trans. Faraday Sa., 51. 1684 (1915) 5) E. U. Franck, D. Hartmann and F. Hensel. Dircusr. Faraday Soc.. 39, 200 (1965) 6) G. J. Hills, P. J. Ovenden and D. R. N'hitehouse, ibid., 39, 207 (1965), P. J. Ovenden,

D. of University of Southampton (1965) 7) \f. Nakahara and J. Osugi, Thu Journal, 47, I (1977) 8) J. Buchanan and S. D, Hamann, Trans. Faraday Soc., 49, 1425 (1913) 9) .~. J. Ellis, 1. Clrem. Sor., (1959) 3689

10) F. H. Fisher, J. Phys. CLenr., 66, 1607 (19621

Thesis for Ph.


Pressure Effect on Conductance of Aqueous Solutions of Potassium Halides 19

other workers. Gancy and Brummerll> have recently made cazeful measurements of the electrolytic

conductivity for the several aqueous 1-1 electrolyte systems fcom 1 to 2300 bars and from 3 to 55°C

and obtained the limiting electrolytic conductivity ratios (,rp/sr)' with the aid of the Debye-Huckel-

Onsager equation, which are fitted to a third-order polynomial in pressure. On the other hand, the

transport number under high pressure, f+ has been measured for aqueous KC1 solutions by a modified

moving boundary method by Wall and Gfll12>, Wall and Berkowi[z131, Kay et al.lt> and Pribadilsl.

Matsubara e6 at 1s. 17) have recently measured the trarsport numbers in aqueous solutions of KCI, KBr

and KI from 1 to 1500kg/cros at l5, 25 and 40°C. There is good agreement among the results of t+

in KCl solution by different workers. Now, we can examine [he data by calculating the limiting molar

conductivity of K* ion, d°(K*) from the different three sources of A-(KCl), A°(KBr) and ~I`(KI) with

transport numbers, in addition to the examination of the data in literatures and discuss the tempera-

ture and pressure effects on the behavior of the constituent ions in water.

Experimental

The conductivity measurements of aqueous solutions of KCI, KBr and KI were carried out at 15,

25 and 40°C under high pressure up to 1500 kg/cm'. The high pressure apparatus and the method of

measurements were already described in the previous paper181. The conductivity cell was of a glass

syringe type made of bdrosilicate. The sample solution in the cell was separated from the pressure-

[ransmitting fluid (Silicone oil) by the glass piston of the syringe. It was assumed that the cell con-

stant did not vary with pressure. The pressure vessel was kept a[ [he definite temperature within

0:03°C by immersing it in a liquid paraffin bath. Pressure was measured with a calibrated Bourdoa tube gauge. The stork solutions (1.0 x 10-°- mol/dms) were prepared with KCI, KBr and KI of guazan-

teed reagent grade dried at 100`C for 5 hr and conductivity water, respectively. The solutions (or

measurements were prepared in the concentration range 2.O X 10-'~S.O x 10-4 mol/dma by dilution

of [be stock solutions. The concentrations of these dilute solution at high pressure were corrected

with the molar volume of water at corresponding pressure calculated by the Tait equation191. The

electric resistance of the solution was measured at the definite temperature and pressure with the

apparatus for measurement of conductivity made by Yanagimoto Co., Ltd., MY-8 type. After corrections of solvent conductance and concentration, the molar conductivity of solution, A(KX)

was determined.

11) 12) 13) 14) 13) 16) 17) 18) 19)

A. B. Gancy and S. B. Brummer, 1. Chem. Eng. Dafa, 16, 383 (1971) F. T. Wall and S. J. Gill, J. Phyt. Chem., 59, 27g (1951) F. T. SVall and J. Berkowitz, ibid., 62, 87 (1938) R. L. Kay, B. S. Pribadi and W. Watsoa, ibid., 74, 2724 (1970) R. 5. Pribadi, J. Safulion Chem., 1, 433 (1972) Y. Matsubara, K. Shimizu and J. Osugi, Thit Journal, 43, 24 (1973)

J. Osugi, 1S. Nakahara, Y. Datsubara and K. Shimizu, ibid., 45, 23 (1973) E. Iaada, R. Shimizu and J. Osugi, ibid., 42, 1 (1972) H. S. Haraed and B. B. Owen, "The Physical Chemistry of Electrolyte Solution" p. 379, Reiahold (1939)


20 R. Sbimizu and N. Tsuchihashi

Results and Considerations

The Rohlrausch relationship in Eq. (1) was so satisfied with the molar conductivities , d(KX) at various concentrations that the limiting molar conductivities, A'(KX) were determined by the extra-

polation of A(KX)~--squaze root of molar concentration plot to zero concentration. The uncertainty

in data was within 1-D.2 ~-' cm'- mol-'.

A(RX)=A°(KX)-SCl/x (1 )

d`(KX) at 1 atm were in good agreement with the values measured by Benson and Gordonzo~ and

Owen and Zeldeszt>. S obtained from the tangent of d(KX)~Ct/z curve were in good agreement with

the values calculated by the Onsager equation of tonduc[ivity with the viscosity and the dielectric

data] under high pressures. As shown in Table 1 and Fig. 1, there is good agreement between the

Table 1 Limiting molar conductivity of potassium halides in aqueous solution, d°(KX)/~-4mZmol'~

RCl

t/1:

P/k rm-'

15 ti

AuthorsGancy and

BrummerAuthors

Gancy andB rummer

40

Authors

1 atm

500

1000

1500

121.1

129.3

125.3

120.2

121.1

124.0

125.3

12i.2

149.9

151.8

152.2

151.3

149.9

151.7

152.0

151.5

1%.3

1%.7

195.5

193. I

ICBr

P/kg em-'

15 25 40

AuthorsCancy and

BrummerAuthors

Gancy andBrummer

Authors

1 atm

500

1000

1500

122.8

725. 1

17a.5

124.5

122.8

] a.1

12a'.7

la. 0

151.8

153.3

152.fi

151.1

151.E

152.9

152.4

151.2

197.7

197.5

195.3

192.5

RI

ist/ro

P/kg ®''

25 40

AuthorsGancy and

BrummerAu [hors

Gancy andBrummar

Authors

1 atm

500

1000

1500

121.8

122.8

1?2.2

120.0

121.8

123.1

1?2.7

121.1

150.4

150.4

148.7

14G.2

150.3

150.2

148.8

146.0

195.5

193.5

189.9

185.3

20) 21) 22) 23)

G. C. Benson and A. R. Gordon, J. C/fern. Plrys., 13, 473 (1945) B. B. Owen and H. Zeldes, ibid.,18, 1083 (1950) J. B. Cappi, Thesis for Ph. D. of London University (1964) H. S. Harped and B. B. Owen, oD. ciG, p. t62


Pressure Effec[ on Conductance of Aqueous Solutions oC Potassium Aalides

~o E

E

q C

21

l54

157

152

157

150

0

e

e

0

x

a

0

0

0e

0

LY

Fig. t Variation of limiting molar tivi[y of aqueous solution

with pressure at 2i C

Q: Authors ~: Ga ncy and Brummer

~; Kakahara et a!. x: Fisher

~: Ovenden

conduc•

of F:CI

0 500 1000 1500 P/kgcm_p

present data of A-(RX) and those calculated with the aid of In (KP/s~)° represented as the third-order polynomial in pressure by Gancy and Brummerlll at 15 and 25°C.

On the other hand, the limiting molaz conducticities of K' ion, .i°(K') were calculated trom A`

(KCl), A`(KBr)and A°(KI) combined with the transport numbers of R` ion, 1, in these solutionsls.n>.

As shown in Table 2, the agreements among a°(K') from three di$erent sources are satisfactory at

Table 2 Limiting molar conductivity of potassium ion in aqueous solution, l'(K`)/3't cm2 mol'~

t/C P/kg cm-' KCI KBr KI Average

s

1 alan

500

1000

1500

59.6

60.3

60.3

59.9

59.7

60.4

60.2

59.6

59.9

60. a

6D. 3

59.7

59.7

so.4

60.3

59.7

1

25

40

1 atm

500

1000.

1500

73.5

73.8

T3.5

72.5

73.3

73.7

73.1

72.2

73.5

73.5

73.1

72.2

73.4

73.7

73.2

72.3

1 alm

5110

1000

1500

95.7

9a.2

94.3

92.7

95.5

95.0

93.6

92.0

95.3

94.4

93.2

91.3

95.5

94.9

93.7

92.0

each temperature. The limiting molar conductivities of halide ions, .i°(X') are also given in Table 3

as the results calculated with the values of .1°(KX) and d`(K•). Fig. 2 shows the variations of the

ratio of the limiting molar conductivity of each ion, Ap /.tr` which are characteristic of [he ions, and

the fluidity ratio of water, r,°/rp°~ with pressure at each temperature.

The decrease of the viscosity of water with increasing temperature shows [hat an increase in

temperature reduces the amount of the three-dimensional hydrogen bond in water. And it should be

extremely pressure dependent because of the voluminous structure of water. Asshowa is Fig. 2,

[he viscosity of water at 15 and 25°C decreases at first and then increases with increasing. pressure.

AC 40`C, it increases monotonously with increasing pressure. This may be ascribed to the reduction


22 K. Shimizu and N. Tsuchihashi

Tahle 3 Limiting molar conductivity of halide ion in aqueous solution,

t/C P/kg ao-' CI' B~' I'

15

1 atm

500

1000

1500

61.5

64.0

65.0

65.3

63.1

64.7

65.3

64.9

6I.9

62.4

61.9

25

1 atm

500

1000

lsoo

76.4

78.0

78.7

7a. s

78.5

79.6

79.5

7a. s

60.3

76.9

76.9

75.6

7a. o

40

latm

500

1000

1500

100.6

101.5

101.1

lOD.4

102.2

102.4

101.6

100.5

100.2

99.1

96.7

93.4

R

R

R4

1.05

i.oa

IS°CC1-

Rr'

~f ~ydo

K•

r

0 soo iooo

P/kgcm'z

isoa

1.05

1.~

og

R

R

K4

0.9 5

as•ccr

sr

f . °i~da

I-

x~

0 500 1000 P/k6cm'2

1500

o~

a

1.00

0.95

-00'C

CI'

Br'

\K• 3~ R \ eo

I-

Fig. 2 V ariations of limiting molar conduc-

tivity ratio of ion aad fluidity ratio

of water with pressure at I5, 25ond

40'C

0 500 1000 P/kgcm'a

1500


Pressure Effect on Conductance of Aqueous Solutions of Potassium Halides 23

of the three-dimensional order in water and then the packing by pressure. So, the structure-breaking

effect on water is induced by pressure as well as temperature.

Gurneyul concluded from the mobilities of K*and CI' ions at atmospheric pressure that the Con-

tributions to the B-coefficient in the Jones-Dole equation o[ viscosity from both ions were the same.

The 8-coefficient is concerned with the ion-solvent interaction. From the analysis of the viscosity

data at atmospheric pressure with this assumption, Nightingale~> has found for the halide ions

except F" ion to have the negative B-toeffitient in the Jones•Dole equation and classified these ions as the structure-disordering ions binding water molecules less firmly than does water itself and

acting as the structure disordering centers to collapse the water structure about ions and thereby

reducing the local viscosity. In mutual comparison of the values of B-coefficient, it was considered

that the structure breaking poccer would increase ih the sequence K*=C1' (Br <I- at atmospheric

pressure. But, Che reliability of this method for evaluation seems to be questionable~l, and it seems difficult Co explain the behavior of these ions in aqueous solution under high pressure from this view

pointr+l asfollows. As shown in Fig. 2, the variation of (dp°/)r`) of Cl- ion with pressure is different from that of K` ion a[ each temperature. This may be due to the differences of the orientation of

hydrating water molecules to the negative center ion and positive one and of the electronegativity

of both ions (the presence of hydrogen bond between CI- ion and water molecules which may be less

firmly than in water itself). In the case of Cl' ion, the mobility of the ion increases with increasing

pressure at 15 and 2S`C, and the difference behveen (.ir°/ds`) and (r,„°/pp°) is positive at I5, 25 and 40`C. This may be ascribed to that the local viscosity o[ water in the neighborhood of the ion in-

creases by the dissolution o[ CI' ion into water at atmospheric pressure. Kamely, CI- ion would

apparently behave like the structure maker in aqueous solu[ion~>. as P' ion, and the amount of

three-dimensional hydrogen band may increase by the introduction of CI- ion into water, even though the interaction is less firmly than in pure water. Therefore, the breaking effect due to pressure in

this solution may be relatively intensified more Chan in pure water at each temperature. On the other

hand, K* ion would be the structure breaker at 1 i and 25°C, because of Che opposed behavior of K*

ion to Cl' ion as shown in Fig. 2, and the structure maker at 40°C.

In contrast with Cl- ion, the mobility of I- ion, on the whole, decreases wit6increasing pressure;

even at 15'C, the increase of the mobility by pressure is little, and the difference between (.4p°/di )

and (>)i /,p°) is always negative at each temperature. The local viscosity of water in [be neighbor-

hood of the ion may decrease by I- ion at atmospheric pressure. In other words, the three-dimensional

order in water would be broken much more by I' ion at atmospheric pressure, so that the structure-

breaking effect due to pressure is weakened. The decrease of the mobility of I' ion by pressure

would be ascribed to the packing effect of pressure on water molecules. The effectiveness of I- ion

24) R. N', Gurney,'Ionic Processes in Solution", p. Ifi7, :4IcGraw Hill (t9s3) 23) E.R. Xightingale, Jr., "Chemical Physics of Iooic Solutions", ed. by B. E. Conway and R. G. Barradas,

p. 87, John R'iley and Sons, (1966) 26j B. E. Conway. J. Solution Chem., 7, i21 (1978)

27) R. L. Kay, "R'a[er;' ed. by F, Franks, vol. 3, p..173. Plenum Press (1973) 28) J. E. Desnoyers and G. Perron, J. Solution Chenr., I, 199 (1972)


24 K. Shlmlzll aad N. Tsurhihashi

and pressure for the structure-breaking effect reduces at 40°C because of [he considerable decrease

of amount of three-dimensional hydrogen bond in water due to an increase of temperature. This

distinguishable difference between Cl- and I- ions may be explained in terms of the ionic radii and

the electronegativity.

The variations of (dr°/A~°) of Br' ion show the similar tendency as those of CI' ion, and Br-ion

has the positive difference between (,ip°/.ir`) and (~i /r)p°) under high pressure at each temperature,

though Br' ion has been considered to be the typical structure breaker because of the negative value

of 8-coefficient.

These explanations for the phenomena are rather qualitative, and the quantitative approaches

based on the statistical calculations will be hoped.

Department of Applied Chemfclry

Faculty of Engineering

DosGishn Unir~errity

Xyoto 602, Japan

title pressure effect on conductance of aqueous solutions...

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