Determination of stability constants by pH titrations: a critical examination of data handling

1978 ◽  
Vol 56 (9) ◽  
pp. 1202-1211 ◽  
Author(s):  
Terrence B. Field ◽  
W. A. E. McBryde
Keyword(s):  
Data Analysis ◽  
Stability Constants ◽  
Input Data ◽  
Equilibrium Constants ◽  
Critical Examination ◽  
Data Handling ◽  
Random Errors ◽  
Selective Electrode ◽  
Methods Of Calculation

Data from simulated titrations (pH, titer, and pM) were generated from literature values of equilibrium constants, and then submitted to various published methods of calculation to regenerate the indicated equilibrium constants. These calculations were done with error-free input data, and the same with imposed random errors. In other experiments data from real titrations were subjected to the same analysis, and additional checks were made on the output of the calculations with an ion-selective electrode as a probe for pM. One method of data analysis was prone to cause errors in the finally recovered constants, and causes for this are suggested.

scholarly journals Thermodynamic and Spectroscopic Studies of the Complexes Formed in Tartaric Acid and Lanthanide(III) Ions Binary Systems

Molecules ◽  
2020 ◽  
Vol 25 (5) ◽  
pp. 1121 ◽  
Author(s):  
Michal Zabiszak ◽  
Martyna Nowak ◽  
Zbigniew Hnatejko ◽  
Jakub Grajewski ◽  
Kazuma Ogawa ◽  
...  
Keyword(s):  
Tartaric Acid ◽  
Stability Constants ◽  
Binary Systems ◽  
Equilibrium Constants ◽  
Spectroscopic Studies ◽  
Luminescence Spectroscopy ◽  
Binary Complexes ◽  
Overall Stability ◽  
The Stability

Binary complexes of tartaric acid with lanthanide(III) ions were investigated. The studies have been performed in aqueous solution using the potentiometric method with computer analysis of the data for detection of the complexes set, determination of the stability constants of these compounds. The mode of the coordination of complexes found was determined using spectroscopy, which shows: Infrared, circular dichroism, ultraviolet, visible as well as luminescence spectroscopy. The overall stability constants of the complexes as well as the equilibrium constants of the reaction were determined. Analysis of the equilibrium constants of the reactions and spectroscopic data allowed the effectiveness of the carboxyl groups in the process of complex formation.

Reactions of gallocyanine methyl ester with gallium(III) and indium(III) ions

1982 ◽  
Vol 47 (7) ◽  
pp. 1950-1963 ◽  
Author(s):  
Milan Kotouček ◽  
Josef Růžička ◽  
Pavla Vaculíková
Keyword(s):  
Methyl Ester ◽  
Stability Constants ◽  
Equilibrium Constants ◽  
Photometric Determination ◽  
Conditional Stability ◽  
Conditional Stability Constants

Reactions of gallocyanine methyl ester with gallium(III) and indium(III) ions in solutions in 15% (m/m) ethanol were studied spectrophotometrically. At pH 1.7-6.5, the GaL, GaL2, and Ga(OH)L3 complexes are formed; in the case of indium, the In(OH)2L2 and In(OH)L3 complexes appear at pH 4-6.5, and InL3B2 in tartrate solutions. The conditional stability constants and the equilibrium constants of the coordination equilibria were calculated, and procedures were worked out for a photometric determination of gallium and for a chelatometric determination of gallium and indium using gallocyanine methyl ester as metallochromic indicator.

Comparison of pyrocatechol violet and aluminon for the determination of 'reactive' aluminium in the presence of organic acids

Soil Research ◽  
2000 ◽  
Vol 38 (4) ◽  
pp. 807 ◽  
Author(s):  
Sahta Ginting ◽  
Bruce B. Johnson ◽  
Sabine Wilkens
Keyword(s):  
Reaction Time ◽  
Stability Constant ◽  
Organic Acids ◽  
Stability Constants ◽  
Equilibrium Constants ◽  
Organic Anions ◽  
Pyrocatechol Violet

The effect of 5 organic anions (citrate, malate, malonate, oxalate, and tartrate) on the concentration of Al measured with 2 colorimetric reagents [pyrocatechol violet (PCV) and aluminon] was determined as a function of reaction time. The results are compared with concentrations of reactive Al [Al3+ + AlOH2+ + Al(OH)2+ ] predicted from stability constants. The PCV reagent was found to overestimate this fraction, i.e. to underestimate the extent of complexation by oxalate, malonate, and malate, even when the shortest reaction time of 30 s was applied. However, the aluminon reagent provided a good estimate of ‘reactive’ Al at the 30 s reaction time in the presence of all organic anions studied. At a citrate and tartrate to Al ratio of 1 : 2, the ‘reactive’ Al concentration, determined from stability constant data, underestimated the extent of Al complexation. These deviations could be modelled by the addition of a further complex, with the composition Al2 (OH)L2+ for citrate and Al2(OH)2L2+ for tartrate. Tentative equilibrium constants for these species are presented.

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

1979 ◽  
Vol 44 (2) ◽  
pp. 374-392 ◽  
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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