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.

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.

103Rh-NMR-Untersuchungen an Chloro-Bromo-Rhodaten(III) und Bestimmung der Stabilitätskonstanten im System [RhClnBr6-n]3-, n = 0-6 / 103Rh NMR Studies of Chloro-Bromo-Rhodates(III) and Determination of the Stability Constants in the System [RhCl„Br6-n]3-, n = 0-6

1989 ◽  
Vol 44 (11) ◽  
pp. 1402-1406 ◽  
Author(s):  
W. Kuhr ◽  
G. Peters ◽  
W. Preetz
Keyword(s):  
Nmr Spectroscopy ◽  
High Resolution ◽  
Stability Constant ◽  
Stability Constants ◽  
Trans Isomers ◽  
Nmr Studies ◽  
Downfield Shift ◽  
Overall Stability ◽  
The Stability

By 103Rh NMR spectroscopy the ten compounds of the system [RhCl„Br6_„]3-, n = 0-6 are identified by separate signals. A downfield shift of approximately 160 ppm is observed per substitution of Cl by Br, and the stereoisomers for n = 2, 3, 4 are separated by at least 4 ppm. From the relative intensities of the 103Rh signals in equilibrated solutions, whose total contents of Rh. Cl and Br are known, six individual stability constants are calculated. Their product gives the overall stability constant, indicating [RhBr6]3- to be 36,300 times more stable than [RhCl6]3-. On treatment of [RhBr6]3- with HCl cis/fac isomers are formed stereospecifically, whereas the reaction of [RhCl6]3- with HBr gives trans isomers, n = 2 and 4, containing 20—30% of the cis compounds; only mer-[RhCl3Br3] 3- is obtained pure. The high resolution spectra of [RhCl6]3- and [RhBr6]3- are exhibit five signals each, reflecting the intensity patterns of the most abundant isotopomers within [Rh35Cln37Cl6-n]3-, n = 2-6, and [Rh79Br„81Br6_„]3-, n = 1-5, respectively.

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.

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.

Characterization of α-Isosaccharinic acid: pKa-determination

2002 ◽  
Vol 757 ◽  
Author(s):  
S. Ekberg ◽  
C. Ekberg ◽  
Y. Albinsson
Keyword(s):  
Stability Constant ◽  
Stability Constants ◽  
Linear Functions ◽  
Acid Dissociation ◽  
Complexation Studies ◽  
Pka Determination ◽  
The Stability ◽  
Isosaccharinic Acid

ABSTRACTThe stability constant for isosaccharinic acid dissociation is of importance in complexation studies involving species present in radioactive waste. As there are very few stability constants reported in the literature, this study has determined stability constants at 22.8, 34.5 and 44.2° C, using potentiometric titrations in a 1 M NaClO4 solution. The stability constants were linear functions of the inverted temperature, thus allowing for a simple determination of the entropy and enthalpy of the reaction.

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