Envlron. Scl. Technol. 1988, 22, 282-286
hydrogen ion activity ionic strength (M) total Co"TSP concentration (M)
aH* P
Redpath, J. L.; Willson, R. L. Int. J. Radiat. Biol. Relat. Stud. Phys. Chem. Med. 1973,23, 51. Schuler, R. H. Radiat. Res. 1977,69, 417. Leung, P. K.; Hoffmann, M. R. J. Phys. Chem. 1985,89,
[Co"%SPIT [Co total ith ConTSP catalytic center concentration (M) TSPlTt Registry No. Co(II)TSP, 29012-54-2; HSC2H,0H, 60-24-2; (HOCzH$)2, 1892-29-1. Literature Cited Sheldon, R. A.; Kochi, J. K. Metal-Catalyzed Oxidation of Organic Compounds; Academic: New York, 1981. Hoffmann, M. R. Environ. Sci. Technol. 1980, 14, 1061. Boyce, S. D.; Hoffmann, M. R.; Hong, P. A.; Moberly, L. M. Environ. Sci. Technol. 1983, 17, 602. Hoffmann, M. R.; Lim, B. C. Environ. Sci. Technol. 1979, 13, 1406.
Dolansky, J.; Wagnerova, D. M.; Veprek-Siska, J. Collect. Czech. Chem. Commun. 1976,43, 2326. Schutten, J. H.; Zwart, J. J. Mol. Catal. 1979,5, 109-123. Schutten, J. H.; Beelen, T. P. M. J. Mol. Catal. 1981, 10, 85-97.
Nriagu, J. 0. Sulfur in the Environment; Wiley-Interscience: New York, 1978. Chen, K. Y.; Morris, J. C. Environ. Sci. Technol. 1972,6, 529-537.
Jones, R. D.; Summerville, D. A.; Basolo, F. Chem. Rev. 1979, 79, 139.
Khan, M. M.; Martell, A. E. Homogeneous Catalysis by Metal Complexes;Academic: New York, 1974; pp 79-180. McLendon, G.; Martell, A. E. Coord. Chem. Rev. 1976,19, 1-39.
Ochiai, E. J. Inorg. Nucl. Chem. 1974, 37, 1503-1509. Boucher, L. J. In Coordination Chemistry of Macrocyclic Compounds;Melson, G. A., Ed.; Plenum: New York, 1979; pp 461-516. Koppenol, W. H.; Butler, J. FEBS Lett. 1977, 83, 1. Mass, T. A.; Kuijer, M. M.; Zwart, J. J. Chem. SOC.,Chem. Commun. 1976, 87. Kundo, N. N.; Keier, N. P.; Glezneva, G. V.; Manneva, E. K. Kinet. Katal. 1967,8, 1325. Simonov, A. D.; Keier, N. P.; Kundo, N. N.; Manneva, E. K.; Glazneva, G. V. Kinet. Katal. 1973, 14, 988. Standard Methods for the Examination of Water and Wastewater, 14th ed.; 1975; p 443. Lazrus, A. L.; Kok, G. L.; Gitlin, S. N.; Lind, J. A. Anal. Chem. 1985,57,917.
5267.
Gruen, L. C.; Blagrove, R. J. Aust. J. Chem. 1973,26,319. Bevington, P. R. Data Reduction and Error Analysis for the Physical Sciences; McGraw-Hill: New York, 1969; p 225.
Beelen, T. P. M.; da Costa Gomez, C. 0.;Kuijer, M. Recl. Trav. Chim. Pays-Bas 1979, 98, 521. Cotton, F. A.; Wilkinson,G. Advanced Inorganic Chemistry, 4th ed.; Wiley: New York, 1980; p 1188. McGinnety, J.; Payne, N. C.; Ibers, J. A. J. Am. Chem. SOC. 1969, 91, 6301.
Terry, N. W.; Amma, E. L.; Vaska, L. J. Am. Chem. SOC. 1972, 94, 654.
Klotz, I. M.; Klotz, T. A. Science (London)1955,121,477. Martell, A. E. Acc. Chem. Res. 1982, 15, 155-162. Wagnerova, D. M.; Schwertnerova, E.; Veprek-Siska, J. Collect. Czech. Chem. Commun. 1974. 39. 1980. Przywarska-Boniecka, H.; Wojciechowski; W. Mat. Sci. 1975, I , 27.
Hoffmann, M. R.; Hong, A. P. K. Sci. Total Enuiron. 1987, 64, 99-115.
Berezin, B. D. Coordination Compounds of Porphyrins and Phthalocyanines; Wiley: New York, 1981; p 66. Stewart, R. The Proton: Applications to Organic Chemistry; Academic: New York, 1985. Perrin, D. D.; Dempsey, B.; Serjeant, E. P. pK, Prediction for Organic Acids and Bases;Chapman & Hall: New York, 1981; p 20. Al-Thannon, A. A.; Barton, J. P.; Packer, J. E.; Sims, R. J.; Trumbore, C. N.; Winchester, R. V. Int. J. Radiat. Phys. Chem. 1974,6,223. Barton,J. P.; Packer, J. E. Int. J. Radiat. Phys. Chem. 1970, 2. 159.
Cabelli, D. E.; Bleiski, H. J.; Benon, H. J. J . Phys. Chem. 1983.87. 1809.
Schenk, 'H. P. Diploma Thesis, Technical University of Berlin (FRG), 1982, pp 49, 67. Schiifer, K.; Bonifacic, M.; Bahnemann, D.; Asmus, K.-D., J . Phys. Chem. 1978,82, 2777-2780. Received for review April 20, 1987. Accepted August 20, 1987. Support for this research was provided by grants from the US. Environmental Protection Agency (R809198-01 and R81161201-0).
Effect of Cosolvents on the Solubility of Hydrocarbons in Water Frank R. Groves, Jr. Chemical Engineering Department, Louisiana State University, Baton Rouge, Louisiana 70803
rn New experimental data are reported on the aqueous solubility of n-hexane in the presence of cosolvents methanol and methyl tert-butyl ether (MTBE) and of benzene with MTBE. These data along with literature information on the benzene-ethanol, benzene-methanol) and hexane-ethanol systems are correlated with the aid of Margules and UNIQUAC activity coefficient equations. A rapid approximate method for predicting hydrocarbon solubility in the presence of a cosolvent is reported. Introduction The transport of spilled organic materials through the environment is a major concern for environmental protection. A current problem is the leakage of gasoline from 282
Environ. Scl. Technol., Vol. 22, No. 3, 1988
underground storage tanks. Leaked organics come into contact with groundwater, gradually dissolve, and are transported through the environment. Modeling of these transport processes requires a knowledge of basic thermodynamic data, including aqueous solubility. Solubility of most pure hydrocarbons is known. However, unleaded gasoline may contain organic octane enhancers, some of which are completely miscible with water. The effect of these cosolvents is to increase the hydrocarbon solubility. The objective of this research is to study the effects of cosolvents on hydrocarbon solubility with special emphasis on gasoline-range hydrocarbons. Specifically, we have investigated the aqueous solubility of benzene and nhexane in the presence of methanol, ethanol, and methyl
00 13-936X/88/0922-0282$0 1.50/0
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Table 1. Literature Data on Ternary Systems ref
system
benzenewater-methanol benzenewaterethanol
%day ( I ) Brandani e t al. (2)
hexane-waterethanol
Ross and Patterson (3)
tert-butyl ether (MTBE). In addition to experimental data, we report empirical correlations of solubility via activity coefficients. An approximate method for rapidly predicting hydrocarbon solubility in the presence of cosolvents is proposed. Previous Work Liquid-liquid equilibrium data were found in the literature (1-3) for several of the systems of interest. Table I lists these systems. Theoretical predictions of solubility are generally based on its relation to the activity coefficient. A t equilibrium, the fugacity of a solute must be the same in the water phase (W) and in the hydrocarbon phase (H):
F=f?
(1)
In terms of activity coefficient yi, mole fraction x i , and standard state fugacity f:, this can be expressed as yyxyj: = y p x r p
(2)
x y = ypxp/yy
(3)
so that
The problem of solubility prediction reduces to calculation of the required activity coefficients. Various empirical activity coefficient correlations have been used for this purpose. Leinonen and Mackay (4) studied the solubility of binary hydrocarbon mixtures and correlated their data with a Redlich-Knter activity coefficient equation. Banejee (5) determined the solubility of mixtures of chlorobenzenes, benzyl alcohol, toluene, and ethyl acetate. The data were successfully correlated by the UNIFAC activity coefficient equation. Munz and Roberta (6) used measurements of Henry's law constant to investigate the effect of solute concentration and cosolvents (methanol and 2-propanol) on the aqueous activity coefficient of certain halogenated hydrocarbons. Measured cosolvent effects were generally less than those predicted by UNIFAC. Experimental Section Solubilities of hydrocarbons in the presence of coaolvents were determined by equilibrating a hydrocarbon layer and
Somple
water Loye7
Pori
Figure 1.
Equilibration flask
a water layer with gentle stirring as shown in Figure 1. The layers were sampled periodically and analyzed by gas chromatography. After a time on the order of 1week, the phase compositions had become constant, indicating that equilibrium was attained. The equilibration flasks were maintained at constant temperature by immersion in a constant-temperature bath controlled to wiithin *O.l deg. Benzene (99.9+%, HPLC grade), n-hexane (99+%), methanol (99.9+%, HPLC grade), and methyl tert-butyl ether (99+%, HPLC grade) were obtained from Aldrich Chemical Co.,and were used without further purification. Ethanol (absolute) was obtained from Midwest Solvents co. Analysis of the hydrocarbon and aqueous layers was done by direct injection of samples into a Hewlett-Packard 5880 Model gas chromatograph equipped with a flame ionization detector and automatic integrator. The column used was 3% SP 1500 on 80/120 CARBOPACK B, 10 f t long, and 1/8-in.diameter. The analysis was run isothermally a t 150 "C with helium carrier gas a t 25 mL/min.
Results Experimental results are shown in Table 11. Pure component solubility data from Sutton and Calder (7) and Polak and Liu (8) are included for comparison. The experimentally determined tie line for the benzene-waterethanol system was compared with the results of Brandani et al. (2) and was found to be consistent with them. The data for methyl tert-butyl ether show that this casolvent concentrates in the hydrocarbon phase and has little effect on hydrocarbon solubility in the water phase. The hexanemethanol data as well as the literature data for hexane-ethanol, benzene-ethanol, and benzene-methanol
Table 11. Exparimental Solubility Data (25 ' C Except for Hexane-Methanol, 30 "C)
solute benzeneb
benzene henzene hexane' hexane hexane hexane hexane hexane
hexane
coaolvent none
ethanol MTBE none
MTBE MTBE MTBE methanol methanol
methanol
aqueous layer' solubility, casolvent wncn, mg/L mg/L 1755 & 30 n 2070 4 63200 f 200 1653 f 8 2619 i 14 12.4 i 0.2 0 2642 i 38 12.9 i 0.6 14.4 i 0.7 3528 f 59 12.2 f 0.4 7 594 f 130 31.2 f 1.0 114600 i 820 218400 i 1400 67.4 f 1.7 367000 i 2680 509 i 18
*
hydrocarbon layer coslolvent wsolvent concn,' partition coeff mg/L Kcs = &I& 2930 i 6 61 130 i 158
4.6
40670 f 770 52690 f 560 i i 7 9 ~ ) *1830 240 i 6 644 i 9.2 1600 f 14
osmgn 0.0093 o.wgn 71.3 53.1 41.6
0.0087
Environ. Sci. Technol.. Vol. 22, NO.3. 1988 283
Table 111. Constants in Activity Coefficient Equations Margules Constants system
AN
A B C
AZI
A13
A31
C*
ASZ
A23
7.812 5.776 0.315 0.614 0.8696 -0.931 8.91 7.812 5.776 1.726 3.88 0.5092 -0.0976 3.2 12.87 7.342 1.920 2.70 0.8693 -1.050 14.75 UNIQUAC Constants
system
a12
a21
a13
A" B C D E
1298 1240 1885 1885 1885
360.2 346.7 572 572 572
-49.2 390.6 587.5 562.5 -300
-239.0 7.812 -140.6 191.2 1150
a23
a32
-568.9 -421.3 -568.9 -421.3 50.0
-393.0 -626.9 -393.0 -626.9 462.5
% error predicted
system
(A) benzene (1)-water (2)-ethanol (3) (B) benzene (1)-water (2)-methanol (3) (C) hexane (1)-water (2)-ethanol (3) (D)hexane (+water (2)-methanol (3) (E) hexane (1)-water (2)-MTBE (3)
hydrocarbon solubility Margules UNIQUAC av max av max 6 48 35
12 56 51
26 33 9 28 11
40 50 20 46 18
"UNIQUAC constants of Brandani et al. (2).
show that these cosolvents, completely miscible with water, can cause considerable increase in the hydrocarbon solubility. The measured cosolvent partition coefficient is shown in the last column of the table. The data were correlated with the aid of the ternary Margules and UNIQUAC activity coefficient equations. Ternary Margules. From Holmes and Van Winkle (9) In y1 = ~2'[A12 + 2~1(A21- An)]
+ ~3'[A13 + 2xi(A,i - Ais)] + + A13 - A23 - A3d/2 + xl(A21 + A12 + A12 + A31 - AIS)+ ( ~ -2 x3)(A23 - A321 - (1- 2x,)C*l
X2X3[(A21
(4)
--
To get y; for other components, one permutes the subscripts 1 2 3 etc. UNIQUAC. From Anderson and Prausnitz (10) In yi = In
(&/xi)
4 ,+ z/2qi In (ei/&) + li - -Cxjlj xi I
-
O!T::
where l j = ( z / 2 ) ( r j- 4,) - (rj - l),7;,= exp(-aij/T), and r,, q . = pure component parameters. The Margules and UNIQUAC parameters were fitted to the experimental tie line data. A computer program for calculating liquid-liquid equilibrium separations (ELIPS, Prausnitz.et al., 11) was used to compute phase compositions from the activity coefficient equations for each experimental tie line. An objective function
was then formed where xjk(i) and xjke(i) are calculated and experimental mole fractions of component k in phase j for tie line i. The Margules and UNIQUAC parameters that minimized the objective function were then found by a pattern search routine. The resulting parameters are shown in Table 111. 284
Environ. Sci. Technol., Vol. 22, No. 3, 1988
In this table the components are designated as follows: hydrocarbon (l),water (2), and cosolvent (3). The hydrocarbon-water (12, 21) constants were obtained from mutual solubility data. The water-cosolvent (23, 32) constants were obtained from binary liquid-liquid or vapor liquid equilibrium data and adjusted where necessary for a better fit to the solubility data. The hydrocarbon-cosolvent (13,31)constants were the chief variables used in the minimization procedure. Table I11 also shows average and maximum errors in fitting hydrocarbon solubility with the activity coefficient equations. The UNIQUAC equation is preferred because it fits the data adequately without requiring a ternary parameter
.
Prediction of Hydrocaron Solubilities When doing fate and transport studies, a researcher will encounter problems of the following kind. Given a hydrocarbon phase containing a known amount of cosolvent, what is the solubility of the hydrocarbon in water? Such problems can be solved with the aid of an equilibrium separation program using the Margules or UNIQUAC equations with the constants of Table 111. However, this is a rather lengthy iterative computation and a quicker approximate method is desirable. Consider the following problem; given the hydrocarbon-phase composition, what is the hydrocarbon solubility in the equilibrium aqueous phase? This problem is relevant for the calculation of the equilibrium between a large amount of hydrocarbon and a small water phase. It also arises as part of an iterative calculation of interphase mass transfer. For a particular iteration, one specifies the composition on the hydrocarbon side at the interface and computes the equilibrium composition on the water side a t the interface. This problem can be solved quickly by using an experimental value for the cosolvent partition coefficient. The hydrocarbon solubility can be calculated directly by eq 3 provided that hydrocarbon activity coefficients are known for the aqueous and hydrocarbon phase. Since the cosolvent content of the hydrocarbon phase is known, an approximate yy can be calculated from the Margules or UNIQUAC equation by neglecting water solubility in the hydrocarbon phase. Now using the experimental partition coefficient for cosolvent, we can calculate the equilibrium cosolvent mole fraction in the aqueous phase:
= Kcsx8s
(7)
The water-phase hydrocarbon activity coefficient (with hydrocarbon mole fraction set a t zero) can then be calculated from the Margules or UNIQUAC activity coefficient equation. The hydrocarbon solubility follows from eq 3. This procedure was used to reproduce the experimental hydrocarbon solubilities. For example, consider the benzene (1)-ethanol (3) data point in Table 11. In this experiment the composition of the hydrocarbon phase neglecting water solubility was x y = 0.9944 and X! = 0.0056. Using these values in the UNIQUAC equations, we can calculate the benzene activity coefficient in the hydrocarbon phase: yy = 1.000. The experimentally measured ethanol partition coefficient was K3 = 4.6. Hence the ethanol mole fraction in the water phase is
x r = 4.6(0.0056) = 0.026
(8)
The water-phase composition, neglecting hydrocarbon solubility, is x y = 0.026 and x y = 0.974. Using this approximate water-phase composition in the UNIQUAC equations, we can compute the benzene activity coefficient
Table IV. Hydrocarbon Solubility by Apbroximate Method (UNIQUAC Predictions)
solute
coso1ute
benzene
methanol
benzene
ethanol
hexane
methanol
hexane
ethanol
hexane
MTBE
mole fraction cosolvent, hydrocarbon phase 0.0007 0.0055 0.0114 0.0056 0.015 0.053 0.123 9.74 x 10-4 2.64 x 10-3 6.54 x 10-3 0.0093 0.0112 0.0149 0.0222 0.0604 0.0783 0.1751
water-phase hydrocarbon mole fraction % error predicted exptl 0.000 97 0.001 7 0.003 9 0.000 66 0.001 1 0.003 5 0.010 5 8.08 X 10" 1.93 x 7.58 X 0.000 23 0.000 44 0.00081 0.001 87 2.57 X 10" 2.54 X 10" 2.34 X 10"
0.0020 0.0026 0.0036 0.0005 0.0010 0.0030 0.0150 7.03 X 1.61 X 1.40 x 0.0003 0.0005 0.0009 0.0018 2.73 X 3.10 X 2.57 X
-52 -35 8 32 10 17 -30 15 20 -46 -23 -12 -10 4 -6 -18 -9
10"
10-4
10" 10"
10"
5.0r
80 H = hexane
f E
40
y h 0 4.0 6.0 8.0 10.0 2.0
xlathanol x
lo3
Flgure 2. Water-hexane partition coefficient for methanol. 0 200
0. I
0.2
H 'atha no I H = benzene
Flgure 5. Water-benzene partition coefficient for ethanol.
0
-: c
c"
2.0r
100
8* 1I
Y
I
I
I
0.005
0.01
0.015
H = hexane
XHmathonoi
Flgure 3. Water-benzene partition coefficient for methanol,
0 IO
0 20
H X MTBE
H=hexane
Figure 8. Water-hexane partition coefficient for MTBE.
1 -
0
001 0 0 2 003
xH
ethanol
Figure 4. Water-hexane partition coefflclent for ethanol.
in the water phase ry = 1510. The predicted benzene solubility in the water phase then is obtained from eq 3: yrxf
q=--rY
(1.00)(0.9944) .\ = u n30066 1510
(9)
The corresponding experimental value is x y = 0.0005. Table IV compares predicted and experimental (including data from ref 1-3) hydrocarbon solubilities in the presence of cosolvents. Figures 2-6 show experimental cosolvent partition coefficients (including data from ref 1-3) plotted vs mole fraction cosolvent in the hydrocarbon
phase. The agreement in Table IV between experimental hydrocarbon solubilities and the predictions by the approximate method is satisfactory. Since the cosolvent partition coefficient may remain approximately the same for other similar hydrocarbons, this approach may have some general applicability including prediction of solubility of hydrocarbon mixtures. Where experimental data are lacking, the UNIFAC equations could supply approximate values of the activity coefficients.
Conclusions New experimental data are reported on hydrocarbon solubilities in water in the presence of cosolvents. The results are correlated satisfactorily by means of Margules and UNIQUAC activity coefficient equations. A simple approximate procedure for predicting hydrocarbon solubility in the presence of cosolvents has been developed. The method gives satisfactory accuracy and is simple Environ. Sci. Technoi., Vol. 22, No. 3, 1988
285
Environ. Sci. Technol. 1988, 22, 286-292
enough for implementation on a programmable calculator or microcomputer. The data and methods reported should be useful for fate and transport calculation for gasolinerange hydrocarbons. Registry No. MTBE, 1634-04-4; hexane, 110-54-3; benzene, 71-43-2; methanol, 67-56-1; ethanol, 64-17-5; water, 7732-18-5.
Literature Cited (1) Triday, J. J. Chem. Eng. Data 1984, 29, 321-324. (2) Brandani, V.; Chianese, A.; Rossi, M. J. Chem. Eng. Data 1985,30, 27-29. (3) ROSS,S.; Patterson, R. E. J. Chem. Eng. Data 1979,24,111. (4) Leinonen, P. J.; Mackay, D. Can. J . Chem. Eng. 1973,51, 230-233. (5) Bannerjee, S. Environ. Sci. Technol. 1984, 18, 587-591. (6) Munz, C.; Roberts, P. V. Environ. Sci. Technol. 1986,20, 830-836.
(7) Sutton, C.; Calder, J. A. J . Chem. Eng. Data 1975, 20, 320-322. ( 8 ) Polak, J.; Liu, B. C. Y. Can. J . Chem. 1973,51,4018-4023. (9) Holmes, M. J.; Van Winkle, M. Ind. Eng. Chem. 1970,62(1), e .
21.
(10) Anderson, T. F.; Prausnitz, J. M. Znd. Eng. Chem. Process Des. Dev. 1978, 17, 552-561. (11) Prausnitz, J. M.; Anderson, T.; Grens, E.; Eckert, C.; Hsieh,
R.; O'Connell, J. Computer Calculations for Multicomponent Vapor-Liquid and Liquid-Liquid Equilibria; Prentice-Hall: Englewood Cliffs, NJ, 1980; p 334. Received for review April 13,1987. Accepted July 16,1987. This work was supported by the Louisiana State University Hazardous Waste Research Center via a grant from the US.Environmental Protection Agency. However, it does not necessarily reflect the views of the Agency, and no official endorsement should be inferred.
Thermodynamics of FishIWater and Octan-I-ol/Water Partitioning of Some Chlorinated Benzenes Antoon Opperhulzen," Peter Sern8, and Jan M. D. Van der Steen Laboratory of Environmental and Toxicological Chemistry, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands The thermodynamic properties of the partitioning of chlorobenzenes between fish and water have been investigated. It is shown that bioconcentration by fish of polychlorobenzenes is accompanied by positive enthalpy and entropy changes. The free energy of this transfer process at room temperature is dominated strongly by the favorable entropy contribution. In contrast, the partitioning of these compounds between octan-1-01 and water is accompanied by negative enthalpy and by small negative or positive entropy changes. These results demonstrate that octan-1-01 is a poor model of the fish lipids and that generally octan-1-ol/water partition coefficients will not give reliable predictions of bioconcentration factors. In particular, the slopes of plots of octan-1-ol/water partition coefficients against bioconcentration factors will not be the same for different compounds. In addition, preliminary results are presented on the extrathermodynamic relationships between molecular structure and enthalpy, entropy, and free energy changes during both accumulation in fish and octan-1-ol/water partitioning of chlorobenzenes.
Introduction Although there are many concerned with the nature of the accumulation of hydrophobic chemicals in fish or other aquatic species, very few data have been reported considering the thermodynamic background of this partition process (1, 2). Generally only relationships between bioconcentration factors (K,) or uptake and elimination rate constants ( k l and kp, respectively) and physicochemical data are presented (3-5). For instance, the relationship between K , and the octan-1-ol/water partition coefficient (Kd,,J has been reported many times (3-7). Use of such relationships presupposes that the thermodynamics of the various partition processes are proportional (8). Equilibrium partitioning of a chemical between two physicochemical phases can be expressed by
lute temperature, and AGO denotes the Gibbs free energy of transfer between the phases. Hence, the relationship between log K,and log Kd,octcan be considered as a relationship between the Gibbs free energies of the two processes, i.e., an example of a linear free energy relationship (LFER) The concept of LFER was initially proposed by Collander (9,IO). Subsequently, such relationships have been reported between various types of liquid-liquid distributions for many types of chemicals. Satisfactory relationships are usually obtained for structurally related compounds. In addition, application of the LFER concepts to other types of distribution processes such as adsorption or solubility also provided satisfactory results (11,12). Relationships between Kd,octand reversed-phase high-performance liquid chromatography (HPLC) retention (13) or Kd,oct and fish bioconcentration factors, for instance, are usually linear, but sometimes significant deviations from linearity have been found (3, 4, 7, 14). Although the concept of LFER is often employed, few studies report on the full thermodynamics of the distribution processes involved. Recently, it has been shown that, even if the free energies of two processes appear to be linearly related, this does not necessarily indicate that the thermodynamic background of partitioning in the two distribution processes is similar (15). In this study, preliminary results are reported for the elucidation of the full thermodynamics of the exchange of hydrophobic chemicals between water and fish and the thermodynamic background of the generally accepted relationship between K , and Kd,oct.In addition, a first attempt is made to find extrathermodynamic relationships between a solute's structure parameters and the partial thermodynamic parameters of the fish/water and octan1-ol/water partitioning, Le., AAG, AAH, and AAS.
.
(1)
Materials and Methods Chemicals. 173-Di-,1,3,5-tri-,1,2,3,4-tetra-,penta-, and
in which R denotes the gas constant, T denotes the abso-
hexachlorobenzene were obtained from Analabs. After
Kd = e-AGO/RT
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