A PROPOSAL FOR THE THERMODYNAMIC AND KINETIC MODELING OF CHEMICAL-REACTIONS IN CLUSTER FORMATION - ILLUSTRATED BY SOOT FORMATION IN LOW-PRESSURE FLAMES

A phenomenological treatment for the thermodynamic and kinetic descrip tion of chemical reactions in the formation of clusters is developed. This theory is valid for isothermal processes in closed systems. It ta kes into account the consumption of the reactants as the reaction proc eeds. The surface of the Helmholtz free energy of the reaction is calc ulated dependent on cluster size and cluster concentration. This surfa ce has a bottom; the bottom begins in the initial state of the system (only reactants are present). It ends at the stable equilibrium (bulk phase in equilibrium with reactants and products). The bottom is assum ed to be the trajectory of the reaction from the initial state to the stable equilibrium of the system. A kinetic rate equation for the reac tion is derived. The rate equation is tested by experimental results. These results are obtained for the combustion of ethine in a low press ure flame by a molecular beam mass spectrometrical technique. Good agr eement is found between the experimental results and the solution of t he rate equation. Various parameters of the reaction can be calculated .