Constant ionic strength, Table

The equilibrium constants K = Kq K[ have been evaluated and the resulting values have been given in Table 4.5. The interaction of lanthanides with perchlorate is strong enough to warrant care in interpreting data on the stability constants in the presence of a large excess of perchlorate used to maintain constant ionic strength. 

In defining 52. pt) a number of assumptions have been made concerning the conventional values of fx ascribed to the individual chemical species involved in the various equilibria (see footnotes to Table I). In particular it was assumed that, at constant ionic strength, fj is also constant and all changes in the activity of X associated with changes in solution composition are attributed to changes in [X]. Consequently, the activity of lead in sea water of constant salinity is proportional to [Pb]. In view of the number of assumptions involved in the... 

With its determination carried out at constant ionic strength the pH, value, so obtained, provides an assessment of the acidity of the amphoteric ion exchanger. This pH, relatable to the average value of pKj and pK2 with Eq. (16), is very close to the value of the isoelectric point 0 )- Paries [105] has pointed out that the relationship between the lEP of a solid surface and the valency-effective ionic radii, when corrected for crystal field effects, coordination, hydration, and other factors, is quite good. He also has indicated that the broad probable lEP range characteristic of a cation oxidation state may be selected from the data in Table 2 as shown below. It is known that the lEP for amphoteric oxides is affected by the presence of impurities, crystallinity and the chemical species under investigation. 

Hydrolysis equilibria can be interpreted in a meaningful way if the solutions are not oversaturated with respect to the solid hydroxide or oxide. Occasionally, it is desirable to extend equilibrium calculations into the region of oversaturation but quantitative interpretations for the species distribution must not be made unless metastable supersaturation can be demonstrated to exist. Most hydrolysis equilibrium constants have been determined in the presence of a swamping inert electrolyte of constant ionic strength (/ = 0.1, 1, or 3 M). As we have seen before, the formation of hydroxo species can be formulated in terms of acid-base equilibria. The formulation of equilibria of hydrolysis reactions is in agreement with that generally used for complex formation equilibria (see Table 6.2). 

A student prepared four saturated solutions by mixing Ca(I03)2 with a strong acid. Excess solid was filtered off. The student found the S for each solution with constant ionic strength, using iodometric titrations. The resulting data are shown in Table 1. 

The aqueous solubility of lomefloxacin was studied (11) as a function of pH and temperature with constant ionic strength of 0.15 M with NaCl. The intrinsic solubility at 25° C was 2.93 x 10 3 M or 1.03 mg ml/1. The aqueous solubility of lomefloxacin mesylate at 25°C and 37°C, pH 5,7, and 9 is given in Table 6. It was found that the presence of metal ions (Al3+, Ca2+, Mg2+ and Fe3+) increased the aqueous solubility of lomefloxacin. In addition, the aqueous solubility of lomefloxacin increased to a constant value with increasing Bi3+, followed by a marked decrease in solubility at higher Bi3+ concentrations. (15). Lomefloxacin is known to bind to all of the above metal ions. (16)... 

A fluoride electrode was used to determine the amount of fluoride in drinking water samples. The results given in the table were obtained for four standards and two unknowns. Constant ionic strength and pH conditions were used. ... 

Table 3-15. In k values of inorganic anions at different pH values but constant ionic strength. (See Fig. 3-59 for chromatographic conditions)...

The study of the variation of the solubility with the selenite concentration is stated to have been carried at the constant ionic strengths 0.01 and 0.3 M. How this was accomplished was not clear from the information in the paper. The data in the tables rather seem to indicate that the ionic strength varied and reached 0.03 and 0.5 M, respectively, in the solution with the highest selenite concentrations. The analysis of the data was made with an equilibrium model that comprised the solubility equilibrium and the formation of the complex 0(8003)2 T us the formation of CoSe03(aq) was not included in the model. The analysis led to values of the solubility product at the two ionic strengths that appear to be inconsistent with the value obtained from the solubility in water. This result together with the improbable model made the review reject the outcome of the equilibrium analysis. 

Table VI. Electrophoretic Mobilities of Some Reservoir Rock Particles at pH 7 in Brines of Different Composition and Constant Ionic Strength (0.406 mol/L)...

A total of 20 mg of each R0-R°° sample (Table 1) was equilibrated at 20°C with 50 mL of 0.02 mol KCl solution to produce a constant ionic strength. The sorption experiments of heavy metals (Cu, Pb, Zn, or Co) were carried out by adding solutions containing fixed quantities of elements as - MeCl2. The amount of each element in the solutions was 50 mmol kg k The samples were maintained at a constant pH (3.0-8.0) kept for 4 h by adding 0.1 or 0.01 mol HCl or NaOH continuously. Competitive adsorption experiments between Zn and Cu were carried out at pH 6.2. Cu and Zn were added as a mixture to ferri-hydrite (R°°), keeping Cu concentration constant (50 mmol kg ) in the presence of different amounts of Zn to produce an initial Zn/Cu molar ratio of 1, 2, 3, 4 or 8. The experiments were carried out at pH 6.2 because previous... 

It should be pointed out that most of the equilibrium constants listed in this table refer to solutions of constant ionic strength with the exception of Butler s data which have been corrected to zero ionic strength. The effect of ion association has also been neglected. The data of Pavarov et were obtained by radiotracer techniques at 18 2°C. 

The values in the tables have not been corrected for complexation with medium ions for the most part. There are insufficient data to make corrections for most of the ligands, and In order to make values between ligands more comparabie, the correction has not been made in the few cases where it could be made. In general the listed formation constants at constant ionic strength include competition by ions from KNO3 and NaC104 and are somewhat smaller than they would be If measured in solutions of tetraalkylammonium salts. 

Calculate the H of a buffer made with analytical concentrations 0.200 M lactic acid and 0.100 M sodium lactate. Repeat after a 100-fold dilution of the solution and compare the need for the full equation (3-2) in each case. Take a constant ionic strength of 0.10 M in both cases and use / values from the Kielland table in Appendix A-1, assuming lactate ion is about the same size as acetate. The reported pX° for lactic acid is 3.858. It is CH3CH(OH)COOH. 

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