Investigations of Complex Precipitation Systems

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

An Apparatus for Synchronized Precipitation under Sterile Conditions

The apparatus for .synchronized precipitation devised earlier1 enables the experimenter to achieve extremely slow and controlled mixing of the reactants and to avoid local supersaturations

Quantitative Assessment of the Effect of Additives on Nucleation, Growth and Aggregation of Crystals

Among the physico-chemical problems associated with biological mineralization the determination of the rates and mechanisms of nuclation, crystal growth and aggregation and the assessment of the effect of potential inhibitors/ promotors thereon deserves particular attention", A typical »in vivo« situation in which these processes are initiated in supersaturated, unseeded solution is crystalluria which is considered to be the initial step in renal stone formation"