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Positive and negative deviations from ideal behaviour in binary mixtures are discussed in relation to the formation of compounds with a stoechiometric composition AuBv. The results are applied to metallic mixtures.

Equilibrium data for the protonation of Wofatit CA-20 at Amberlite IRC-50 are measured at three NH 4 Cl concentrations. The data are used, via a three-parameter model, to estimate limiting values of the protonation constants.

It is shown that the Langmuir isotherm corresponds to a constant equilibrium quotient of the corresponding ion-exchange reaction, i.e. ideal behavior. Such behavior in ion exchange is so rare that it has little practical use.

Methods for treating acid-base titration data on chelating resins are described and applied to the computer-assisted regression program IONEX with the regression procedure MINOPT. In this approach nonideal behavior in the exchanger phase is taken into account by the Högfeldt three-parameter model. Regression analysis is applied to data on Ligandex-I studied by Szabadka and the results compared with those from a least squares program. The two approaches give identical results. The application of regression analysis program is further illustrated on titration data from a commercial chelate exchanger Iontsorb Salycil 100.

Titration data on carboxymethyldextran, CmDx, formerly treated by using the protonation reaction, are here treated by considering the ion exchange reaction. As expected the two approaches are equivalent, although the former treatment allows direct comparison with protonation constants of the monomer in the literature. It is demonstrated that the parameters of one approach can be computed from the other. The ratios [A]r/[A]soln of the two components are also treated. They are sensitive to experimental errors and their use should be discouraged. Deviations from ideal behavior are accounted for by a simple three-parameter model.

From acid-base titrations of carboxymethyldextran (HP) the equilibrium "constant" for the reaction H+ (aq) + P- rlhar2; HP (K) has been computed. This quantity varies with the degree of dissociation, α, indicating nonideal behavior. The data have been fitted to a three-parameter model, which takes nonideality into account. The model gives a satisfactory fit to data pH(v). Moreover, the three-parameter model offers an estimate of the intrinsic protonation constant, giving log Kint = 3.39 ∓ 0.03. The data also permit an estimate of the equilibrium constant for the reaction H+ (aq) rlhar2; H+ (CmDx); i.e., the free energy of proton transfer at infinite dilution from the aqueous phase to the polyelectrolyte at infinite solution giving δG = -4.67 kJ.

Water sorption on an ion exchanger can be described by formation of several hydrates. The general least squares program WSLET based on the “pit-mapping” approach has been written for evaluating such equilibria. It is written in FORTRAN 77 for use on personal computers. Besides finding the best values for the equilibrium constants of the various hydrates the program also searches for best values of the stoichiometric indices by using the so-called ESI-method. The program is provided with least-squares procedures and blocks for statistical analysis of the residuals as well as for data simulation. It has been tested with data on the strong base resin Dowex 1 as well as on simulated data. In the present paper an illustrative example is given together with data simulation. It is found that in most cases WSLET helps to find a better fit than earlier models quite efficiently, showing the advantage of the ESI method in combination with least-squares methods.

2-(2-, 3- and 4-pyridyl)-3-hydroxythiophenes and 4-(2-, 3- and 4-pyridyl)- 3-hydroxythiophenes have been prepared by hydrogen peroxide oxidation of the corresponding boronic esters. In the former case the boronic esters were obtained in three steps from 2,3-dibromothiophene via the corresponding 3-bromo-2-pyridylthiophenes synthesized by Pd(0)-catalyzed coupling between 3-bromo-2-trimethylstannylthiophene and the corresponding bromopyridines. In the latter case the known isomeric pyridylthiophenes were converted into the corresponding boronic esters in three steps via tribromo- and 3-bromo-4-pyridylthiophenes successively. 4-(3- and 4-pyridyl) thiophen-2(5H)-ones were also obtained in the syntheses of 4-(3- and 4-pyridyl)-3-hydroxythiophene. They are suggested to arise from rearrangement during the halogen-metal exchange. Spectroscopic investigations by 1H NMR and IR show that these hydroxythiophene systems exist exclusively as enol forms.

Four methods of estimating equilibrium constants in ion exchange have been compared. While three methods give results in good agreement, the fourth sometimes fails due to the fact that the location of an inflexion point does not always coincide with that corresponding to the equilibrium constant.

The formation of oligomers by the five sulphoazoxines Napthylazoxine 6S, SNAZOXS and 2-, 3-and 4-CAPAZOXS was studied potentiometrically. Two pH scales were used. Either proton activity was measured and the system was calibrated with standard buffers, or the hydrogen ion concentration was measured and the system was calibrated externally in terms of h=[H+]. At concentrations higher than 1 mmol dm–3 dimers and trimers are formed, for which a reaction scheme is proposed. The concentration scale (h) gives more precise and more accurate values for the formation constants because external calibration of the glass electrode cell in terms of log h is more accurate than calibration with different NBS buffers. The main reason is that calibration with buffers is carried out in a medium very different from that used in the actual titration. The algorithm used has almost no influence on the precision of the formation constants in comparison with the reproducibility of the titration.

The sensitive response of weak-acid ion exchangers to counterion concentrations in the aqueous phase has been attributed to a Donnan potential term. By correcting for this term a constant p K ina has, in a number of cases, been resolved for the repeating unit at each point of their titration with base. It has been suggested that this approach leads to the resolution of the intrinsic p K ina of the weak-acid functionality repeated in these ion exchangers. In other cases, however, this approach has not led to a constant p K ina. An error in the Donnan term introduced by macroporosity of these exchangers has been suggested as the source of this incongruity. A method based on the premise that the Donnan term is uniquely responsible for the variability of the uncorrected p K ina has been outlined and shown to give a satisfactory result.

Donnees sur l'echange des ions ethylammonium primaires secondaires tertiaires et quaternaires en presence de l'acide dinonylnaphtalene-sulfonique (echangeur de cations liquide) dans de l'heptane, du nitrobenzene et de l'ethyl-2 hexanol. Donnees, aussi, sur l'echange en presence de l'echangeur de cations solide, le KRS-8

Water sorption, heat effects and IR spectra have been studied as a function of water activity for dinonylnaphthalene sulfonic acid (HDNNS) dissolved in heptane. The water sorption data have been interpreted in terms of a set of simple equilibria HDNNS + n H , 2 O ⇌ HDNNS ( H 2 O ) n with the equilibrium constants and species given in Table 1. The heat data have been fitted with the same species and the ΔH°-values given in Table 2 together with the entropy values obtained from a combination of heat and free energy data. The large negative entropy values indicate strong ordering effects in the HDNNS-micelles. The infrared data also indicate that in the HDNNS-aggregates the water is more structurized than in resinous cation exchangers of the polystyrene sulfonic acid kind. They also give some information about the first steps of the hydration process beginning with a break up of the HDNNS-aggregates followed by the formation of hydronium sulfonate. Upon the addition of further water molecules this highly symmetric structure is destroyed.

Solvent-impregnated polystyrene beads have been used by a number of workers and their properties investigated [1--17]. Most of the work has been performed with commercially available extractants such as di-2hexylphosphoric acid, tributylphosphate, tertiary amines and some LIX reagents. Only in a few cases were the capacities determined and data given on the stabilities of the samples prepared. In this study, dinonylnaphthalene sulfonic acid (HDNNS) is used. Some preliminary work with this substance was carried out by Soldatov et al. [18,19]. The present paper gives some results on the stability of Amberlite XAD-2 resins impregnated with HDNNS solutions in toluene as well as the dependence of selectivity upon capacity by studying the system N a + H +. A detailed report of this work will be given elsewhere [20].

The system H(+)Na(+) has been studied on Sephadex C-25 and C-50 at two ionic strengths by potentiometry. The data have been fitted by the Högfeldt three-parameter model. For ionic strength 0.100 M (Na)ClO(4) an excellent fit is obtained with a standard deviation of +/-0.013 for both gels. For ionic strength 0.010 M (Na)ClO(4) a satisfactory fit could only be obtained by excluding the lowest and highest pH-value for each gel.

Ion exchange, water uptake and VPO studies have been performed on the two liquid cation exchangers, dinonylnaphthalene and didodecylnaphthalene sulfonic acids and some of their salts. It is found that didodecylnaphthalene sulfonic acid is slightly less aggregated than dinonylnaphthalene sulfonic acid, its water uptake is also less, but the selectivity is about the same. In heptane the presence of water increases the aggregate size, in benzene this increase is smaller and in chloroform no increase is observed. It is also demonstrated that in the concentration range used, the size of a certain aggregate is practically constant. It has been possible to follow the change in aggregate size during the ion exchange process for the system Al3+ - H+. The fact that the three parameter model applies suggests that the interactions at an exchange site are practically independent of aggregate size.

The ion exchange equilibrium of H+ with Ag+, Co2+ and Cd2+ has been studied using the liquid cation exchanger didodecylnaphthalene sulfonic acid (HDDNS) in heptane at 298 K. In the aqueous phase [(H+,Mz+) No3− or Cl] the total anion concentration was kept at 0.100 mol/L. The data have been treated with the Hogfeldt three-parameter model applied to free energies (logκ), water uptake during ion exchange (W) and average degree of association (n). The applicability of the model is clearly demonstrated, since a satisfactory fit is obtained for all three quantities.

Ion exchange and water sorption data for the systems (K,H)D and (Ca,H)D (D = dinonylnaphthalene sulfonic acid) in heptane-isooctanol mixtures can be described by a simple equilibrium model for formation of mixed micelles. This model gives the following relation between the experimental quantity Y and the corresponding quantities yi relating to the two pure micelles and the mixed micelle Y=y 1 X 2 +y 2 (1- X ) 2 +2y 3 (1- X ) X = equivalent fraction of metal ion in the organic phase. This equation can be identified with the relation Y=y 1 X +y 2 (1- X )+y′ 3 X (1- X ) used to fit experimental data Y( X ) . The quantity y3 is computed from y 3 = (y 1 +y 2 +y′ 3 2 Both extraction and IR data show that isooctanol forms complexes with the sulfonate partly blocking the ion exchange process.

Equilibria between dilute sulfuric solutions and trilaurylamine (TLA) in toluene have been studied at 298 K using the two-phase emf-titration method. The data can be explained by the following reactions: In this description no distinction is made between HSO4 - and SO4 2-.

A simple model assuming three kinds of micelles has been applied to the K + H + exchange on dimonylnaphtalene sulfonic acid (HDNNS) in the solvents: chloroform, carbon tetrachloride, nitrobenzene and isooctanol, to the Ca 2+ H + exchange in heptane, nitrobenzene and isooctanol. In heptane the following exchanges were also studied: Ag + H + , Cu 2+ H + , Ni 2+ , Fe 3+ H + and Al 3+ H + . Also the water uptake was studied for Ca 2+ H + and K + H + in nitrobenzene as solvent. The three parameters, found to fit each system are collected in Table 2. At present no simple rationalization of these constants seems possible.

The formation (protonation) constants log K i , of the acid H j L are determined by regression analysis of potentiometric titration data when common parameters (log K i , i = 1,…, j ) and group parameters ( E 0 ′, L 0 , H T ) are refined. The influence of three kinds of error on the protonation constants has been investigated: error from the strategy of minimization, random error, and error from uncertain estimates of group parameters. An analysis of variance of the log K i , matrix was made for 7 identical titrations and 8 computational strategies, or of 7 identical titrations and 8 different options of group parameters to be refined. The influence of the standard potential E 0 of the glass-electrode cell on the systematic error in log K is greater than that of the acid concentration ( L 0 ) or the concentration of titrant used ( H T ). The ill-conditioned group parameters should be refined together with the common parameters ( K i ), otherwise the estimates of log K i , are not accurate enough. Two ways of calibrating the glass electrode cell were compared. Internal calibration (performed during titration) was more accurate than external calibration done separately. Of the programs tested ESAB and ACBA are the most powerful because they permit refinement of group parameters and internal calibration. Citric acid was chosen as model substance.

The three-parameter model introduced earlier has been applied to a strong-acid resin, a strong-base resin, a complex-forming resin and a liquid cation exchanger. In all cases the model gives a satisfactory fit to the experimental data. Using empirical relations between model parameters and divinylbenzene or water content a considerable data reduction is obtained.

Since linear, weak-acid polyelectrolytes respond to neutral salt just like their crosslinked analogs, their equilibria have been presumed to be as amenable to analysis with the Gibbs-Donnan approach as the gels. To examine this possibility this approach has been used to estimate solvent uptake by carboxymethyldextran and poly(acrylic acid) in the course of their neutralization with standard base. These estimates have been compared with estimates obtained for the same parameter by using the ion-condensation model of Manning.

The application of the Hogfeldt three-parameter model to ion exchange data is reviewed. The few cases where it does not work are also mentioned. The model is simple and straightforward to use, and it compares favorably with more elaborate methods for treating weak-acid and complex-forming resins.

The extraction of tracer Hg(II) from aqueous HBr solutions can be described by the reaction HgBr 2 (aq) ⇌ HgBr 2 (org) This reaction has been used to test various conventions for the single-ion activity of bromide ion as well as chloride ion using data already published. It is found that {X−} = yx−C (yx− given by a simple semiempirical equation cf. below) and {X−} = C give a good fit, but the popular function {X−} = y±C does not work at all. It thus seems that it is better to use the stoichiometric concentration than its product with the mean ionic activity coefficient, and this simple convention for ligand activity might be a useful starting point when evaluating complex formation in concentrated electrolytes. The extraction of HgBr2 by TLAHBr (TLA = trilaurylamine) dissolved in benzene can be fairly well described by the reaction TLAHBr(org) + HgBr 2 (aq) ⇌ TLAHBr·HgBr 2 (org) and the stoichiometric distribution coefficient D can be given by D = KD° (α1,0 + α1,0) where K is a constant and α1,0 + α1,1 the fraction of TLAHBr not containing acid in excess of the 1:1 composition.

The following equations has been applied to ion exchange equilibria: Y = yAxA + yBxB + BxAxB where Y is the quantity studied, xA and xB are the fractions of the two components in the binary mixture considered, yA and yB are values of the quantity Y for pure A and B, while B is a quantity taking care of deviation from additivity. The following systems from the literature have been treated: 1. (1) (C2H5)4N+−H+ exchange, as well as water uptake during exchange on KRSx8. 2. (2) Water and methanol (MeOH) uptake from their mixtures by the resin AV-17x8 in sulfate form. 3. (3) Cs+ − Na+ exchange on Dowex 50 of various crosslinkings. 4. (4) Ag+ −Na+ exchange on Dowex 50x8 and x16. It is found that all ion exchange equilibria as well as water uptake during exchange can be fitted with above equation with B = O or B = constant. The uptake of water and MeOH from their mixtures seems to require more complicated expressions. It is shown that for B = 0 the systems behave as regular solutions. It is possible to fit the ion exchange equilibria between Cs+ and Na+ with only four constants, giving a reasonably good fit both with composition and degree of crosslinking from 2 to 16% DVB.

An approach to behavior in concentrated electrolytes is presented. Utilizing the fact that a unique ion activity function was obtained for H30(+) in several strong acids it was possible to calculate ion activity and ion activity coefficient for the ions in the systems LiC1--H20 and LiBr--H20 over a wide composition range. The results indicate that free Li(+) carries about three water molecules even in the most concentrated solutions and C1(-) and Br(-) are unhydrated in the region 12 m to saturation. The decrease in activity functions for C1(-) and Br(-) (seen in the highest concentrations of the salt solutions) is interpreted as due to ion-pair formation. It is assumed that the ion activity coefficient function of C1(-) and Br(-) would be constant in the high salt concentration if no ionpairing occurred and deviations permit the calculation of approximate values for the degree of dissociation of the ion pair.