M,olecular Physics
Chemical Engin
Iring
IN
M
*
THE PAST chemical engineers have been characteristically different from other kinds of engineers, in that their training in chemistry has made them more aware of the molecular approach to industrial problems. I n the future the uniqueness of the chemical engineer should be maintained by preserving the academic bonds with chemists of all branches. I n recent years much has been accomplished in the physics side of physical chemistry-that is, the field of “chemical physics” or “molecular physics”-and it was the purpose of this symposium to point out some of the work which is 01. will be of interest to industrial chemists and chemical engineers. The three subdivisions made for the organization of the symposium were : quantum mechanics, statistical mechanics, and kinetic theory. These three basic disciplines have in the past 15 years yielded practical results; more useful results are forthcoming. Use of these subjects for solving practical problems is tied in closely with the rapid development of high-speed computing machines, which make it possible to evaluate many of the complicated integrals appearing in the theoretical formulas. Quantum mechanics is the basis for discussing molecular structure and such related subjects as dipole moments, quadrupole moments, polarizabilities, and optical spectra. The industrial chemist is interested in these subjects in connection with the synthesis of new polymers, new solids, and new lubricants which will exhibit given mechanical, optical, thermal, and chemical
Reprints of this group of articles may b e purchased a t $1.00 for single copies or for $0.75 each, in lots of ten or more. Address Special Issue Sales Department, American Chemical Society, 1 155 16th St. N.W., Washington 6, D. C.
properties. We are a long way from a complete understanding of these problems via quantum mechanics, but some industries are supporting considerable research in these areas. Statistical mechanics draws upon quantum mechanics in two ways: first, in establishing the theory of statistical mechanics, and secondly, in developing expressions for the intermolecular force fields needed for substituting in the statistical formulas. These formulas give the relation between the bulk equilibrium properties (equation of state, thermodynamic properties, surface tension, phase equilibria) and the intermolecular forces plus the properties of molecules. The applications to the equation of state at very high temperatures is of interest in connection with ballistics and riuclear energy problems. The applications to the equilibrium properties of plastics have shed new light on the role of the chain strucfure in determining compressibility. The applications to electrical properties of gases and liquids may enable the chemist to get molecular diameters and attractive forces from electrical measurements. Kinetic theory (or “nonequilibrium statistical mechanics”) concerns itself primarily with the transport processes in fluid systems. Isotope separation methods -by barrier diffusion and by thermal diffusion-are studied with the help of kinetic theory. Transport processes in the very ‘low density gas region-which have long been of importance to the aerodynamicistare important in chemical engineering in connection with certain problems in catalysis and mass transfer. Transport processes in chemically reacting systems have been studied from a macroscopic point of view by chemical engineers, but kinetic theory studies may well offer new insight to the solution of some of the unsolved problems in this area.
R. B. BIRD University of Wisconsin Madison, Wis. , VOL. 50, NO. 7
Chairman
JULY 1958
1021
