Conference paper

Investigations of Complex Precipitation Systems

H. Furedi-Milhofer ; Laboratory for Precipitation Processes, »Ruder Boskovic« Institute, Zagreb, Yugoslavia

Abstract

A survey of methods available for investigations of complex
precipitation systems under dynamic conditions and under conditions
of stable and metastable equilibrium is represented. Examples
given pertain to the calcium and magnesium phosphate and
calcium oxalate precipitation systems. Solubility curves as well as
precipitation curves and diagrams yield information on the influence
of reactant concentrations (and/or concentrations of other
solution constituents) on the properties of precipitates. Characteristic
parts of precipitation diagrams are the precipitation boundary
(boundary between metastable and unstable solutions) and the
boundary between the concentration regions within which heterogeneous
and homogeneous nucleation respectively prevail. At equilibrium
the precipitation boundary enables calculations of solubility
and complex stability constants, otherwise it yields information
on the kinetics of mononuclear crystal growth. From the
heterogeneous/homogeneous nucleation boundary the critical supersaturation
for homogeneous nucleation and the interfacial energy
and critical radius of the respective homogeneous nucleus may be
determined.
Kinetic experiments give information on the rates and mechanisms
of the rate determining precipitation processes involved.
It has been shown that in the concentration region of heterogeneous
nucleation crystal growth and subsequent (or simultaneous) aggregation
are rate determinant, whereas in the homogeneous nucleation
region aggregation of particles is dominant in all stages of
precipitate formation and the formation of colloids (hydrophobic
precipitates) and highly hydrated precursors (hydrophilic precipitates)
may be expected. Examples of kinetic curves pertaining
to the heterogeneous and homogeneous nucleation region respectively
are presented.

Keywords

Hrčak ID:

194576

URI

https://hrcak.srce.hr/194576

Publication date:

5.11.1980.

Visits: 631 *