Determining stability constant by calvin and melchior
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NTRODUCTION
Mercapto compounds have several applications in biological, pharmaceutical and other chemical fields and are well
known to form complexes with various metals. Gupta and coworker have carried out significant investigation on the
electrochemical behavior of several biologically active organo-sulphur compounds and their complexation behavior
with metals [8,9,10].
Carboxy methyl mercapto succinic acid has coolant additive with corrosion inhibitor and scale preventive property
[4]. The complex ester of CMMSA may be used directly as lubricants or may be blended with other mineral or
synthetic lubricants and various additive and it is also used as adhesive,oxidation inhibitor, detergents and corrosion
resisting agents[1,14,5].In view of wide pharmaceutical and analytical applications of CMMSA, it seems interesting
to study the complexation equilibria of CMMSA with some transition metals in 40%(v/v) methanol – water mixture.
This communication reports the formation, stability constants, and thermodynamic parameters of Ni2+ , Cu2+ ,Mn2+
,
complexes with CMMSA employ potentiometric technique. The log Kstab values determined at 25°
,35°
,and 45°C by
Calvin and Melchior’s extension of Bjerrum’s method [3,2].The stability constant have been further determined by
correction term and Schroder’s convergence formula[6,11].
MATERIAL AND METHODS
All the chemicals used for experiment, such as methanol, potassium nitrate, nitric acid and CMMSA. etc were of
analytical grade, Double distilled water was used in preparation of various solutions. All the metal ion solutions
were prepared in double distilled water and standardized by using conventional procedures[12].A carbonate free
sodium hydroxide was used as a titrate and standardized against oxalic acid. The pH measurements were carried out
with 335-Systronic pH meter (accuracy±0.05 units) using glass and calomel electrode. The electrode system was
calibrated by using standard buffer solutions of pH 4.00, 7.00, 9.2. The empirical correction to pH meter reading in
methanol medium was corrected according to Van-Uitert and Hass relation[13].The following sets of titrations were
performed under nitrogen atmosphere at ionic strength µ = 0.1 M (KNO3)at temperature 25°
,35°
,45°C in 40%
methanol – water mixtures against 0.1 M NaOH .The temperature were controlled by an electrically maintained
thermostat.
(i) Free HNO3 (2.0 X 10 -3 M)
(ii) Free HNO3 (2.0 X 10 -3 M) + Ligand (2.0 X 10 -3 M)
(iii) Free HNO3 (2.0 X 10 -3 M) + Ligand (2.0 X 10 -3 M) + metal ion solution
(4.0 X10 -4).
The log Kstab values determined at 25°
,35°
,and 45°C by Calvin and Melchior’s extension of Bjerrum’s method
[3,2].The stability constant have been further determined by correction term and Schroder’s convergence
Mercapto compounds have several applications in biological, pharmaceutical and other chemical fields and are well
known to form complexes with various metals. Gupta and coworker have carried out significant investigation on the
electrochemical behavior of several biologically active organo-sulphur compounds and their complexation behavior
with metals [8,9,10].
Carboxy methyl mercapto succinic acid has coolant additive with corrosion inhibitor and scale preventive property
[4]. The complex ester of CMMSA may be used directly as lubricants or may be blended with other mineral or
synthetic lubricants and various additive and it is also used as adhesive,oxidation inhibitor, detergents and corrosion
resisting agents[1,14,5].In view of wide pharmaceutical and analytical applications of CMMSA, it seems interesting
to study the complexation equilibria of CMMSA with some transition metals in 40%(v/v) methanol – water mixture.
This communication reports the formation, stability constants, and thermodynamic parameters of Ni2+ , Cu2+ ,Mn2+
,
complexes with CMMSA employ potentiometric technique. The log Kstab values determined at 25°
,35°
,and 45°C by
Calvin and Melchior’s extension of Bjerrum’s method [3,2].The stability constant have been further determined by
correction term and Schroder’s convergence formula[6,11].
MATERIAL AND METHODS
All the chemicals used for experiment, such as methanol, potassium nitrate, nitric acid and CMMSA. etc were of
analytical grade, Double distilled water was used in preparation of various solutions. All the metal ion solutions
were prepared in double distilled water and standardized by using conventional procedures[12].A carbonate free
sodium hydroxide was used as a titrate and standardized against oxalic acid. The pH measurements were carried out
with 335-Systronic pH meter (accuracy±0.05 units) using glass and calomel electrode. The electrode system was
calibrated by using standard buffer solutions of pH 4.00, 7.00, 9.2. The empirical correction to pH meter reading in
methanol medium was corrected according to Van-Uitert and Hass relation[13].The following sets of titrations were
performed under nitrogen atmosphere at ionic strength µ = 0.1 M (KNO3)at temperature 25°
,35°
,45°C in 40%
methanol – water mixtures against 0.1 M NaOH .The temperature were controlled by an electrically maintained
thermostat.
(i) Free HNO3 (2.0 X 10 -3 M)
(ii) Free HNO3 (2.0 X 10 -3 M) + Ligand (2.0 X 10 -3 M)
(iii) Free HNO3 (2.0 X 10 -3 M) + Ligand (2.0 X 10 -3 M) + metal ion solution
(4.0 X10 -4).
The log Kstab values determined at 25°
,35°
,and 45°C by Calvin and Melchior’s extension of Bjerrum’s method
[3,2].The stability constant have been further determined by correction term and Schroder’s convergence
adarshhoax:
sorry it's "INTRODUCTION ".
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