Determination of Small Stability Constants. A Spectrophotometric Study of Copper(II) Chloride Complexes in Hydrochloric Acid.

The absorption spectra of Fe(II)-chloride solutions were measured in both the UV (ultraviolet) and near-IR (near infrared) regions at temperatures ranging from 10 to 100°C with chloride concentrations from 0.1 to 16 mol kg-1. The stability constants of all Fe(II)-chloride complexes were derived from the spectra using a non-negative nonlinear least-squares computer program (SQUAD). Earlier work on this system reported in the literature was rigorously reassessed. The activity coefficients of the ionic species were calculated using both the Pitzer model and the Helgeson model. The results obtained with UV and near-IR spectra and with different activity coefficient calculation models are in general agreement. Other useful thermodynamic data, including the Gibbs energies, enthalpies, and entropies for complex formation, were also obtained. It was found that the Fe(II)-chloride complexes gradually undergo a configuration transformation from octahedral to tetrahedral coordination as the temperature and (or) chloride concentration increases. This coordination change is of significant importance to the nuclear reactors, as the presence of the tetrahedral complex can increase the solubility of iron in steam generator crevices.Key words: Fe(II)-chloride complexes, stability constants, solution thermodynamics, spectrophotometry, reactor chemistry.

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Separation of Lead, Cadmium, and Iron in Analyses of Soil Samples

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19950938 ◽

1995 ◽

Vol 60 (6) ◽

pp. 938-949 ◽

Cited By ~ 4

Author(s):

Ladislav Svoboda ◽

Tomáš Šafařík ◽

Uwe Schmidt

Keyword(s):

Hydrochloric Acid ◽

Soil Extract ◽

Soil Samples ◽

Hydrochloric Acid Concentration ◽

Chloride Complexes ◽

Lead And Cadmium ◽

Selective Detector ◽

Aas Method ◽

Basic Anion

The conditions of sorption of chloride complexes of Pb2+, Cd2+, Fe2+, and Fe3+ ions from media of hydrochloric acid have been studied with a strongly basic anion exchanger - Ostion LG AT. The experiments used an exchanger microcolumn connected with atomic absorption spectrometer as a selective detector of metal ions. From the relation found between retention of the ions studied and hydrochloric acid concentration, conditions of separation have been suggested and used for separations of small amounts of lead and cadmium from many times higher amounts of iron and aluminium in soil extract before determination of both the foreign metals by means of AAS method. The yield of separation exceeded 95%.

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Spectrophotometric study of complexation equilibria and of a method for the determination of Fe(III) ions with 4-(2-pyridylazo)resorcinol and 4-(2-thiazolylazo)resorcinol

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19790374 ◽

1979 ◽

Vol 44 (2) ◽

pp. 374-392 ◽

Cited By ~ 14

Author(s):

Ellena Russeva ◽

Vlastimil Kubáň ◽

Lumír Sommer

Keyword(s):

Stability Constants ◽

Spectrophotometric Determination ◽

Equilibrium Constants ◽

Spectrophotometric Study ◽

Component Concentration ◽

Optimum Conditions ◽

Ferric Ions ◽

Absorption Coefficients ◽

Basic Parameters

The composition, molar absorption, coefficients, equilibrium constants and stability constants for the MLH, ML, M(LH)2 and ML2 complexes have been determined graphically using slope-intercept transformations and numerically from the absorbance-pH curves and from the absorbance dependence on the component concentration, using the PRCEK III and SPEKTFOT programs, or from the continuous variation plots using the JOBCON program. The optimum conditions were found for a spectrophotometric determination of ferric ions with TAR and PAR reagents in pure solutions. The basic parameters of the analytical curves were evaluated using the STAT program.

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