stability constant


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stability constant

[stə′bil·əd·ē ‚kän·stənt]
(chemistry)
Refers to the equilibrium reaction of a metal cation and a ligand to form a chelating mononuclear complex; the absolute-stability constant is expressed by the product of the concentration of products divided by the product of the concentrations of the reactants; the apparent-stability constant (also known as the conditional- or effective-stability constant) allows for the nonideality of the system because of the combination of the ligand with other complexing agents present in the solution.
References in periodicals archive ?
Stability Constant of EBT-M Complexes The complex reactions follow the equation
Assuming 1: 1 stoichiometry, the stability constant of the complex ([K.sub.stab]) can be determined using the phase-solubility diagram according to the following equation:
where Kc is the stability constant (l .mol) the dissociation degree and C the concentration of the complex which is equal to the concentration of drug.
We illustrate the kind of behaviour of the stability constant [C.sub.h] that we wish to exhibit and explain in this paper, for the implicit midpoint rule and the backward Euler time-stepping schemes.
pH 6.0 74 8.0 [Et.sub.2]Cit-Ca [Cl.sub.2] system reaction order (n) 2.03 2.46 2.73 stability constants [10.sup.0.93] [10.sup.2.06] [10.sup.3.06] ([K.sub.s]) rate constant (k)/L x 9 120 4571 [mol.sup.-1] x [s.sup.-1] reverse reaction rate 0.04 0.52 19.80 constant ([k.sub.re])/L x [mol.sup.-1] x [s.sup.-1] [Na.sub.3]Cit-Ca [Cl.sub.2] system reaction order (n) 2.16 2.44 3.0 [K.sub.s] [10.sup.198] [10.sup.246] [10.sup.4.83] k/L x [mol.sup.-1] 60 289 13489 x [s.sup.-1] [k.sub.re]/L x 0.03 0.15 6.79 [mol.sup.-1] x [s.sup.-1] Table 2: Elemental analysis data and Ca content measured by the ICP of complex Ca[Et.sub.2]Cit.
Comparison of stability constant values for Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with thymidine for 1:1 complexes are Cu(II)>Ni(II)< Co(II)[approximately equal to]Zn(II)>Mn(II), which is in agreement with Irving-Williams [15] natural order.
Lin & Horvath [7] investigated the divalent metal ion stability constants for tartrate complexes and proposed the use of a mixture of 0.2 mM tartaric acid and 0.2 mM ethylenediamine at pH 4.5.
where [[lambda].sub.0] is the distribution constant in the absence of HA/FA, [lambda] is the distribution constant in the presence of HA/FA, logK is stability constant of arsenic/HA or FA complex, x is number of tool HA/FA that combine with 1 tool arsenic, and [HA] is concentration of HA/FA in tool per L.
The relative stability constant [beta]1 was calculated from the following Equation:
The percentage of organic solvent in the medium also affects the stability constant values, indicating a competition between the organic solvent and the ligand for the coordination sphere of the metallic ion.
The apparent stability constants, [K.sub.S], were calculated from the straight line of the phase solubility diagrams, assuming a 1: 1 stoichiometry, using
(1) We report for the first time the interaction between FOS and [beta]-CD in water, and we also provide the stability constant value of the FOS/[beta]-CD inclusion complex, in water, at 25[degrees]C.

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