SVIBOR - Project code: 1-07-077


Strossmayerov trg 4, HR - 10000 ZAGREB
tel.: +385 1 459 44 44, fax: +385 1 459 44 69


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Project code: 1-07-077

Physical Chemistry of Colloids, Interfaces and Electrolytes

Main researcher: KALLAY, NIKOLA (19896)

Type of research: basic
Duration from: 01/01/91. to 12/31/96.

Papers on project (total): 65
Papers on project quoted in Current Contents: 30
Institution name: Prirodoslovno-matematički fakultet, Prirodoslovni odjeli, Zagreb (119)
Department/Institute: Laboratory of Physical Chemistry
Address: Marulićev trg 19/II
City: 10000 - Zagreb, Croatia
Phone: 385 (0)1 446 528
Fax: 385 (0)1 446 528
Phone: 385 (0)1 446 001

Summary: The project deals mainly with the development of theoretical models, mathematical interpretation and measurement methods. The comparison of theoretical predictions with experimental results enables development and testing of theoretical and experimental approaches. The aims of the project belong to the field of fundamental physical chemistry, but in some aspects (ecology, technology, corrosion) the applied aspects are also considered. The results were published, and the list of publications is enclosed. In addition, several publications are in press or submitted. The project consists of several topics. CHEMOMETRICS Two new statistical tests were designed and successfully applied for the assessment of the effective rank of spectral data matrices, enabling reliable determination of the number of spectrally active species. Total least squeres method was applied as a step in target factor analysis. An original program package for factor analysis of chemical data was conceptualised and partly developed, including some original concepts in the data weighting, principal component analysis and target factor analysis. IONIC EQUILIBRIA By analysing UV/VIS and Raman spectra of aqueous solutions of several inorganic salts (lithium nitrate, lithium sulphate, magnesium nitrate, magnesium sulphate, cobalt(II) nitrate, cobalt(II) sulphate) in a wide concentration range the presence of associates (ionic pairs and/or complexes) was detected. This was made possible owing to own chemometric methods (see above). SOLUBILITY It was established that surfactant solubility is determined by the equilibria involving micelles characterized cmc dependence on the electrolyte concentration and ion exchange equilibrium constant. The precipitation in surfactant mixture may be successfully interpreted on the basis of the regular solution theory. The dissolution of surfactants is followed by water cluster (iceberg) formation and consequently by temperature dependence of enthalpy and entropy, due to significant change of the heat capacity. Accordingly, the logarithm of the solubility is not a linear function of the reciprocal thermodynamic temperature. The dissolution of gel phase is accompanied with the negative heat capacity change which is explained on the basis of synergistic effect of the chains in the nett structure of the gel. MICELLES AND MICROEMULSIONS The theoretical interpretation of the conductivity of micellar systems and microemulsions were developed and experimentally verified. In the case of micelles, the "true" cmc, equilibrium constant of counterion association and micellar size could be obtained. In the case of water-in-oil microemulsions, for viscous oils the insight into surfactant hydration and the water content in droplets may be achieved, while for nonviscous oils the interpretation on the basis of the charge fluctuation theory provides information on the droplet structure, size and the surfactant shell thickness. ADSORPTION The application of the surface complexation model to the adsorption experiment design, yields the ionization state of the adsorbed organic molecules, binding equilibrium constant and provides the insight in to the interfacial layer structure. These results are relevant to ecology (migration of pesticides in soil). ELECTRICAL INETRFACIAL LAYER The interpretation of the adsorption data in the systems of different permittivities resulted in the value of the electrokinetic slipping plane separation. The mass titration method for the point of zero charge determination was refined so that it can be used for unpurified samples. The accuracy of the method enabled the determination of the enthalpy of surface deprotonation and protonation. Previous calorimetric measurements were not able to distinguish between the contributions of different reactions taking place at the interface and the electrostatic effects. The theoretical consideration resulted in a special experimental design whereby these problems can be solved. The electrostatic effect on the enthalpy of charging the metal oxide interface was examined. COAGULATION AND ADHESION The adhesion method for point of zero charge (pzc) determination of conductive surfaces was developed. This method enabled, for the first time, the determination of pzc values of numerous metals. The effect of thin (hydro)oxide layer was established. The method was successfully applied in corrosion studies. The calorimetry method for examination of kinetics of dissolution of CaCO3 in EDTA was developed.

Keywords: Surfactants, solubility, calorimetry, electrical interfacial layer, metal oxides, microemulsions, micelles, adsorption, adhesion, isoelectric point, electrokinetics, factor analysis, ionic association, ionic pair, orthogonal regression, principal components analysis, Raman spectroscopy, total least squares

Research goals: CHEMOMETRICS Development of numerical and statistical methods of data processing and analysis (mainly for spectrometric data): bi- and trimodal factor analysis (principal components), statistical weighting, orthogonal multilinear regression (known also as Total Least Squares, TLS), nonlinear models. IONIC EQUILIBRIA Detection, identification and characterization of chemical species (ion pairs and/or complexes) formed in concentrated electrolyte solutions. STRUCTURE OF ELECTROLYTE SOLUTIONS Inferring the molecular structure of chemical species present in concentrated aqueous solutions of electrolytes, as well as supramolecular structures (associates, possibly quasi-phase). SOLUBILITY To investigate the complex solubility of inorganic salts and ionic surfactants with respect to the complex nature of the solution i.e. the existence of the soluble species such as ion pairs, complexes, micelles and mixed micelles. To find the relationships which describe the equilibria and kinetics in such systems. To determine the temperature dependence of these equilibria and to compare the results (enthalpy, entropy, heat capacity change) to the calorimetric data. MICELLES AND MICROEMULSIONS To investigate micelles and microemulsion formation equilibria, by taking into account association of chains and counterions, and to develop the experimental methods for characterization of such systems (conductometry, potentiometry, light scattering). ADSORPTION Development of the adequate model of interpretation of adsorption equilibria in the systems with metal oxides dispersed in the solutions of organic substances and surfactants. The examination of the electrostatic effects by considering the data at isoelectric point. ELECTRICAL INTERFACIAL LAYER To develop an adeqate model for describing the equilibria in the interfacial layer and to distinguish between the different contributions to the enthalpy of the surfaces processes. To compare potentiometry and calorimetric data. COAGULATION AND ADHESION To relate the kinetics of these processes to the equilibrium state of the solid/liquid interface. To develop the adhesion method for isoelectric point determination of conductive surfaces and to apply this method for studying the corrosion processes.


  1. Name of project: Interaction of Pesticides and other Organic Substances with Soil Colloids
    Name of institution: Institut fuer Angewandte Physikalische Chemie, Forschungszentrum Juelich
    City: Juelich, Njemačka

  2. Name of project: Electrokinetic Phenomena in Ceramic Materials
    Name of institution: US National Bureau of Standards
    City: Washington DC, USA


  1. Name of institution: Institut fuer Angewandte Physikalische Chemie, Forschungszentrum Juelich
    Type of institution: State institute
    Type of cooperation: Joint project
    City: Juelich, Njemačka

  2. Name of institution: US National Bureau of Standards
    Type of institution: State institute
    Type of cooperation: Joint project
    City: Washington DC, USA

  3. Name of institution: Universitat Maria Curie Sklodowska
    Type of institution: University/Faculty
    Type of cooperation: Systematic exchange of information
    City: Lublin, Poljska

  4. Name of institution: Institut Jožef Štefan
    Type of institution: State institute
    Type of cooperation: Systematic exchange of information
    City: Ljubljana, Slovenija

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Last update: 08/20/95