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

摘要

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 AgI colloid system consists of three consecutive processes. First, a stable sol containing stable particles is produced by mixing [NaI] and [AgNO_3] solutions in appropriate concentrations. After addition of a coagulator to the stable sol, small stable AgI 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.%Na temelju eksperimentalnih i teorijskih razmatranja pokazano je da je koagulacija reakcija 2. reda kojom nastaju agregati veličine šest primarnih čestica. Grafički je pokazano da se teorijske funkcije dobro poklapaju s teorijskima. Opisani su nedostaci teorije koagulacije Smoluchowskoga. Dokazano je, da se tom teorijom ne može protumačiti koagulacija velikih agregata od nekoliko stotina primarnih čestica. Jednadžbe te teorije nisu jednadžbe reakcija 2. reda, kakve bi morale biti, i ne mogu se prilagoditi eksperimentalnim krivuljama. Elektronskim mikrografijama i shemom je pokazano, da se koagulacija koloida AgI sastoji od tri konsekutivna procesa. Najprije nastane miješanjem otopina NaI i AgNO_3 pogodnih koncentracija stabilan sol. Nakon dodatka koagulatora stabilnom solu, male stabilne čestice u sudarima uslijed Brovraova gibanja stvaraju veće čestice, dok te ne postanu primarne čestice radiusa jednakog radiusu iz Debve-Hueckel-ove teorije. Te se sakupljaju u rastuće porozne agregate. Između primarnih čestica u agregatima se nalazi otopina. Mjerena promjena intenziteta raspršenog svjetla s vremenom suma je padajuće funkcije stabilnih čestica i rastuće funkcije agregata. Drugi korijen intenziteta svjetla na stabilnim česticama ili agregatima je proporcionalan veličini stabilnih čestica ili agregata i njihovoj koncentraciji.