Extraction constant determination

Assuming that the two aminophenols behave independently and using the value of the extraction constant determined for the two different aminophenol complexes separately (A l and K2), calculate y and z, which are the concentrations of the two different bis-Schiff-base complexes. Each of these complexes contains two of the same Schiff-base ligands. Any increased amount of extraction above that calculated by this method is assumed to arise from the formation of mixed Schiff-base complexes. 

In a simple liquid-liquid extraction the solute is partitioned between two immiscible phases. In most cases one of the phases is aqueous, and the other phase is an organic solvent such as diethyl ether or chloroform. Because the phases are immiscible, they form two layers, with the denser phase on the bottom. The solute is initially present in one phase, but after extraction it is present in both phases. The efficiency of a liquid-liquid extraction is determined by the equilibrium constant for the solute s partitioning between the two phases. Extraction efficiency is also influenced by any secondary reactions involving the solute. Examples of secondary reactions include acid-base and complexation equilibria. 

Johansson, P.-A. Gustavii, K., Potentiometric titration of ionizable compounds in two phase systems. 3. Determination of extraction constants, Acta Pharm. Suecica 14, 1-20 (1977). 

Biological. o-Phthalic acid was tentatively identified as the major degradation product of di-.n-octyl phthalate produced by the bacterium Serratia marcescens (Mathur and Rouatt, 1975). When di-.n-octyl phthalate was statically incubated in the dark at 25 °C with yeast extract and settled domestic wastewater inoculum, no degradation was observed after 7 d. In a 21-d period, however, gradual adaptation did occur, resulting in 94 and 93% losses at concentrations of 5 and 10 mg/L, respectively (Tabak et ah, 1981). In the presence of suspended natural populations from unpolluted aquatic systems, the second-order microbial transformation rate constant determined in the laboratory was reported to be 3.7 + 0.6 x lO L/organism-h (Steen, 1991). 

The product was extracted with ethyl ether and after evaporation of the solvent the dry residue was recrystallized from CCl AtCHjCOOH was identified by ion-exchange chromatography. Its dissociation constant determined by the measurement of its distribution between... 

Fig. 11. Plot of initial cation transport rates for various carrier/alkali picrate pairs versus equilibrium extraction constants log Ke the points are experimental data, the curve is calculated [6.1, 6.4,6.17]. For analytical reasons the Ke values were determined in conditions different from those of the transport experiments the carriers are cryptands (for [2.2.C5] and [2.1.C5] see structures in [6.1]) dibenzo-18-crown-6, DB18-6 and valinomycin, VAL picrate, P.

Molecules that self-assemble into reverse micelles with low surfactant properties are generally efficient extractants (such as HDEHP, TBP, malonamides, etc.). Their adsorptions at the interface permit the complexation of the aqueous solute and their low surfactant properties permits the avoidance of the formation of very stable emulsion. Hence, ions are extracted, but typically there is less than one water molecule per ion extracted. Exact determination of coextracted water is still important, however, for interpreting the conductivity values and for evaluating the polar core volumes. Typical values are found for the Hamaker constant, because polar cores are supersaturated salt solution. 

The sample volume also has an effect on both the rate and recovery in SPME extractions, as determined by extraction kinetics and by analyte partition coefficients. The sensitivity of a SPME method is proportional to n, the number of moles of analyte recovered from the sample. As the sample volume (Vs) increases, analyte recovery increases until Vs becomes much larger than the product of K, the distribution constant of the analyte, and Vf, the volume of the fiber coating (i.e., analyte recovery stops increasing when KfeVf Vs) [41]. For this reason, in very dilute samples, larger sample volume results in slower kinetics and higher analyte recovery. 

The soot obtained was collected, and carefully treated with o-xylene at 40°C during 24 h. Extracts were filtered, placed into analytical flasks and diluted to the constant volume of 100 ml. Concentrations of individual fullerenes in the extracts were determined by HPLC (LIQUOCHROME 2010 apparatus with a UV detector operating at 330 nm) and UV-Vis (Hitachi U2001 spectrometer) techniques. 

The extraction kinetics of Ni(II) and Zn(II) with //-alkyl-substituted dithizone (HL) in chloroform has been studied by HSS method [7]. The observed extraction rate constants was linearly proportional to both metal ion concentration in the aqueous phase [M2+] and ligand concentration in the organic phase [HL]0, and inversely to the hydrogen ion concentration [H + ] in the aqueous phase. Thus, the rate law for the extraction was determined as... 

For practical heterogeneous catalyst kinetics this principle has the following consequence. Usually, the assumption of a homogeneous surface is not valid. It would be more realistic to assume the existence of a certain distribution in the activity of the sites. From the above, certain sites will, however, contribute most to the reaction, since these sites activate the reactants most optimally. This might result in an apparently uniform reaction behaviour, and can explain why Langmuir adsorption often provides a good basis for the reaction rate description. This also implies that adsorption equilibrium constants determined from adsorption experiments can only be used in kinetic expressions when coverage dependence is explicitly included otherwise they have to be extracted from the rate data. 

Table 3 lists the extraction constants of the bases used as test samples. These were determined by partition in an aqueous organic system. (E AX = conditional extraction constant). 

The calculation results are shown in table II. We also report formation constants determined from spectrophotometry for Ho and Nd, and by solvent extraction for Er. Without going into detail for these two methods, it may be noted that the results show fair agreement. That fact points out the inner sphere character of orthophenanthrolinium lanthanous complexes. The main absorption band of Am (III] is modified by the presence of orthophenanthroline. We used these spectral variations to calculate the formation constants of Am (III], as described in the previous paragraph. As for azide complexes, we observed that Am monoorthophe-nanthroline is more stable than the equivalent lanthanide complex, and for the bis orthophenanthroline species, the difference... 

The extrapolation procedure used in this review is the specific ion interaction model outlined in Appendix B. The objective of this review is to provide selected data sets at standard conditions, i.e., among others, at infinite dilution for aqueous species. Equilibrium constants determined at different ionic strengths can, according to the specific ion interaction equations, be extrapolated to / = 0 with a linear regression model, yielding as the intercept the desired equilibrium constant at / = 0, and as the slope the stoichiometric sum of the ion interaction coefficients, As. The ion interaction coefficient of the target species can usually be extracted from As and is listed in the corresponding table of Appendix B. 

The details of 3c, iR and 3 Ip n.m.r. spectra for a range of carbamoylmethylphosphine oxides have been reported. From this data a correlation between 3ip chemical shift and the nitric acid extraction constant has been determined. 

From the pump the fluid travels to a heated zone, where it becomes supercritical, and then to an extraction vessel where the sample is contained. The extraction vessel and connecting tubes are housed in an oven, so the temperature is kept constant during extraction. Density determines the extraction efficiency and is dependent on pressure and temperature in the supercritical zone. It is essential to maintain a rigorous control of both parameters during the extraction. 

This is a study of the complexation of zirconium by hydroxide using the solvent extraction technique. Experimental work in the study was conducted at 25°C and in 1.96 M (Li, H)C104. Benzene was used as the organic phase and thenoyltrifluoroacetone (TTA) as the extractant. The hydrolysis data was analysed using the previously determined stability constants determined by Solovkin and Ivantsov [66SOL/IVA] using the same technique. The study therefore suffers from the same deficiencies as before and as such cannot be recommended. 

In the second step, with the hydrolysis constants and the specific interaction parameter for ZrOH" and for Zr3(OH) fixed to the values optimised as detailed above, the equilibrium constants and interaction parameter for all other species in the overall hydrolysis model were obtained by a global fit of the potentiometric, solubility, solvent extraction and ion exchange data mentioned above. The fit was extended to the determination of equilibrium constants for heterogeneous reactions ion exchange constants, solubility constants and liquid/liquid distribution coefficients. The fit was based on a preselection of the stoichiometries of dominant species which included invariably the species Zr(OH)4(aq), Zr ) ), Zr (OH)Jj and Zr4(OH)i6(aq) and various other mono-, di-, tri- and tetravalent species to improve the fit. The potential formation of chloride complexes of Zr was considered for chloride containing solutions, using the stability constants determined in Section V-4. If all fitted results were found insensitive to the equilibrium constants of a given species, the respective species was removed from the list of species. 

Nici Nicij were assumed to be nearly constant with increasing MCI concentration, and were included in the reported formation constants (see discussion on [89BJE]). The method used by the author is more appropriate to the study of weak complex formation than the constant ionic medium principle if very high and varying concentrations of a complex-forming anion is used, (see discussion on [89BJE]). Nevertheless, the formation constants determined in this way are not compatible with the log P° values extracted from the SIT analysis... 

P. A. Johansson, B. Karlberg, and S. Thelander, Extractions Based on the Flow Injection Principle. Part 4. Determination of Extraction Constants. Anal. Chim. Acta, 114 (1980) 215. 

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