Showing papers in "Journal of Chemical & Engineering Data in 1967"

A brief review and table of semiempirical parameters used in the Hueckel molecular orbital method

Abstract: I N VIEW of the growing interest in the possibility of correlating Hiickel Molecular Orbital (HMO) calculations (38) with biochemical and biological activities (72, 75, 79, 941, and the application of quantum chemistry to drug design (89) , the authors have calculated electron charge distributions of selected cholinesterase inhibitors (80) and are in the process of applying quantum chemistry to our search for effective antimalarials. Two restrictions became apparent a t the onset of these calculations: Parameters were assigned to a limited number of heteroatoms only, and the choice of parameters for a specific heteroatom was dependent upon the method of derivation. With this in mind, the authors decided that a useful contribution to the field would be the publication of a table of the currently available semiempirical parameters and their corresponding derivations and applications, so that other workers would not find it necessary to duplicate this relatively tedious search for the “right” parameter.

Surface Tension-Viscosity Relationship for Liquids.

Abstract: Water A Benzene 0 Argon . where, A = yN. At T, Equation 2 satisfies _the boundary condition that as ~ L V 0, exp. ' l B i i q q I ' 0. When ql >> vu, which is a t T << T,, Equation 1 is obtained. I n the vicinity of the critical temperature, when q L makes a sizable contribution, considerable deviations from linearity are observed when Equation 1 is employed. The author selected several liquids where data are available over an appreciable temperature interval to demonstrate the validity of Equation 2. These data are plotted in Figure 1. Apparently, argon is the only liquid for which there are extensive and reliable data near the critical region. Here, the agreement is excellent. The discrepancy between the literature values of for water in the critical temperature region makes the extension of the plot to the region doubtful ( 3 ) . For all the liquids quoted by Pelofsky, as well as those shown in Figure 1, the plots pass through the origin. As has been indicated by Pelofsky, the slope may be an indication of the surface tension of the substance at the temperature where q = a. Table I attempts a correlation between the temperature where q --+ m and the temperature of homogeneous nucleation. Homogeneous nucleation as opposed to heterogeneous nucleation results from a spontaneous phase change without the assistance of impurities. The principal component of the energy barrier in homogeneous nucleation is the thermal energy that keeps two particles from clustering together. A special feature of nucleation phenomena is that in forming particles of a new phase, energy is required to form the new surface. Opposing these forces are the intermolecular attractive forces. When the

Solubility of anhydrite in several aqueous salt solutions between 250.degree. and 325.degree.

Abstract: The solubility of anhydrite in several aqueous salt solutions has been determined for temperatures between 250/sup 0/ and 325/sup 0/C and at pressures just above the vapor pressure. The data obtained are intended to be of practical interest in connection with scale precipitation in field heaters during wet steam or hot water injection for thermal oil recovery. The salt solution used contained such electrolytes as sodium chloride, sodium nitrate, calcium chloride, magnesium chloride, sodium sulfate, and magnesium nitrate. Solubility data are determined for a number of binary, ternary, and quarternary systems. (25 refs.)