Measurement of Complex Formation Process of Nickel (II) with Freshwater Fulvic Acids Using the Solubility Method

The complex formation process between Ni(II) and fulvic acids has been studied through the solubility method at pH = 9.0. The old suspension of Ni(OH)2 is used as a solid phase. Fulvic acids are isolated from Paravani lake by the adsorption-chromatographic method. The activated charcoal is used as a sorbent. The concentration of fulvic acids in model solutions changes from 1.1 × 10-5 mol/L to 4.4 × 10-5 mol/L. The value of molar mass of fulvic acids at pH = 9.0 was taken into consideration for the calculation of molar concentrations of fulvic acids. Before adding the ligand the initial concentration of nickel was 3.8 × 10-6 mol/L. This article has shown that, during complex formation process every 0.25 part of an associate of fulvic acids (Mw = 7610), inculcates into nickel's inner coordination sphere as an integral ligand, so it may be assumed, that the average molecular weight of the associate of fulvic acids which takes part in complex formation process equals to 1903. This part of the associate of fulvic acids was conventionally called the "active associate". The average molecular weight of the "active associate" was used for determining the concentration of free ligand and average stability constant (1:1), which equals to β = 1.07 × 107 (lgβ = 7.03).

Thermodynamic and detailed kinetic study of the formation of orthophthalaldehyde-agmatine complex by fluorescence intensities

The aim of this work is to determine the thermodynamic parameters and the kinetics of complex formation between orthophthalaldehyde (OPA) and agmatine (AGM) in an alkaline medium (pH 13). Firstly, the association constant (Ka) between orthophthalaldehyde and agmatine was determined at different temperatures (between 298 K and 338 K) with a step size of 10 K. Secondly, the thermodynamic parameters such as standard enthalpy (ΔH°), standard entropy (ΔS°),and Gibbs energy (∆G) were calculated, where a positive value of ΔH° (+45.50 kJ/mol) was found, which shows that the reaction is endothermic. In addition, the low value of ΔS°(+0.24 kJ/mol) indicates a slight increase in the disorder in the reaction medium. Furthermore, the negative values of ΔG between −35.62 kJ/mol and −26.02 kJ/mol show that the complex formation process is spontaneous. Finally, the parameters of the kinetics of the reaction between OPA and AGM were determined as follows: when the initial concentration of AGM (5 × 10−6 M) is equal to that of the OPA, the results show that the reaction follows an overall 1.5 order kinetics with an initial rate of 5.1 × 10−7Mmin−1 and a half-life of 8.12 min. The partial order found in relation to the AGM is 0.8. This work shows that the excess of OPA accelerates the formation reaction of the complex.

Investigation of Complex Formation Process of Copper with Macromolecular Organic Substances, Isolated from Natural Waters

Natural macromolecular organic substances-fulvic acids take an active part in complex formation processes and stipulate migration forms of heavy metals in natural waters The calculation of the migration forms of heavy metals is one of the problematic issue of the contemporary chemistry, which couldn’t be solved without using the conditional stability constants of fulvate complexes. In spite of researches, experimental data on stability constants of complex compounds of fulvic acids with heavy metals ( among them copper) are heterogeneous and they differ in several lines from each other. One of the reason of such condition is ignoring an average molecular weight of the associates of fulvic acids, which finally causes the wrong results. Complex formation process between copper (II) and fulvic acids was studied by the solubility method at pH=9.0. Cu(OH)2 suspension was used as a solid phase. Fulvic acids were isolated from Paravani lake by the adsorption –chromatographic method. In this article is shown that, during complex formation process every 1/4 part of an associate of fulvic acids(Mw=7610), inculcates into copper's inner coordination sphere as an integral ligand, so it may assume, that the average molecular weight of the associate of fulvic acids which takes part in complex formation process equals to 1903. This part of the associate of fulvic acids was conventionally called an“active associate".The average molecular weight of the“active associate”was used for determination the composition of copper fulvate complex, the concentration of free ligand and stability constant, which equals to 2,25x107

The interaction of morin and morin-5’-sulfonic acid with lead(II): Study of the 1:1 complex formation process in aqueous solution

This article focuses on the aqueous complexation between two flavonoids (morin and morinsulfonate) and Pb2+ at constant ionic strength I=0.5 M (NaClO4). The determination of stability constants of ML complexes were performed at wide pH range. Two obtained constants are 14.8 ± 0.1 and 15.2 ± 0.1 logarithmic units for morin and morin-5’-sulfonic acid, respectively. For estimating the thermodynamic stability of the complexes studied, the Def2-SV(P)/DFT/PBE0/SMD method has been used. Different computational models were tested to describe the data obtained. The theoretical values of logK reproduce the experimental parameters within reasonable errors.

Accretion theory of ideation: evaluation regimes for ideation stages

This paper presents an exercise on theory building to characterise design ideation. It starts by examining how early ideas are defined and evaluated in the literature. An essentialist view is identified that explains the creativity of a final design solution by the creative qualities of early ideas attributed by external judges. Criteria for a theory of ideation that does not rely on the primacy of essence are enumerated. Advanced professional practice is examined to understand evaluation of early ideas ‘in the wild’. Accretion is then introduced as an analogical model to imaginatively drive definitions and conjectures about idea formation in the co-evolution of problem and design spaces. Vignettes from ideation episodes are used to illustrate an accretion theory of ideation. An accretion theory supports new ways to think about ideation as a complex formation process where creative solutions emerge from the synthesis of a multitude of fragmentary and partial ideas – or ‘ideasimals’. An accretion theory of ideation helps to explain the creative value of a final design solution without relying on early ideas having a creative essence, because the creativity of a solution is viewed as emergent rather than present in early versions. An accretion lens is used to suggest new ideation metrics to study the qualities of idea fragments and the process of idea formation. Definitions and relevant assessment regimes for different stages of ideation are discussed. The paper concludes with a discussion on entailments of an accretion theory and next steps for this theory building enterprise.