Pregledni rad

Theories of Colloid Chemistry Based on the Point Charge Double Layer Model

Mirko Mirnik ; Laboratory of Physical Chemistry, Faculty of Science, University of Zagreb, 10001 Zagreb, P.O.B. 163, Croatia

Sažetak

In the introduction, the most important colloidal systems and processes which serve for development and checking of the theories of the field, are stressed. On the basis of experimental and theoretical considerations, coagulation is proved to be a process of second order by which small aggregates of up to six singlets are formed. It is graphically demonstrated that the theoretical functions match the experimental ones in an impressive way. The shortcomings of the classical Smoluchowski's (1916) theory are described and proofs are given that the same theory is not a theory of second order reactions, as it should be, and that it cannot be used for explaining of coagulation of big aggregates.
By electron micrographs and by a scheme, it is demonstrated that coagulation in the Agl colloid system consists of three consecutive processes. First, a stable sol containing stable particles is produced by mixing [Nal] and [AgNC^] solutions in appropriate concentrations. After addition of a coagulator to the stable sol, small stable Agl particles in Brownian motion collide and coalesce and primary particles or singlets are formed. The singlets coagulate and form aggregates consisting of increasing numbers of singlets. The space between the singlets in aggregates is filled with intermicellar liquid. The experimental time evolution of the intensity of scattered light is the sum of the decreasing intensity of stable particles function and the increasing intensity of the aggregates function. The square root of the intensity of light scattered, or absorbed, on stable particles or aggregates is proportional to the size of the stable particles or to the number of singlets in the aggregates. Four methods for determination of the half-life or half-period of coagulation from scattered light intensities are described. The theory is supported by experiments of Agl coagulation with two concentrations of [KNO3], published by Novicki, W., Novicka, G., in J. Chem. Educ. 68 (1991) 523-525.

Ključne riječi

Hrčak ID:

135951

URI

https://hrcak.srce.hr/135951

Datum izdavanja:

4.3.1996.

Posjeta: 504 *