Ninth Report of the Committee on Atomic Weights of the International Union of Chemistry

Abstract

The following report of the Committee covers the twelve-month period September 30, 1937, to September 30, 1938.1 Only one change has been made in the table of atomic weights, in the case of phosphorus from 31.02 to 30.98.Carbon.-Moles and Escribano2 have redetermined the densities of oxygen and carbon dioxide at different pressures.

Some Free-energy Data for Typical Hydrocarbons Containing Six or More Carbon Atoms.

“…In passing, it is worth noting that these third-law values yield AF^s.ie = 970 cal. for the isomerization reaction cyclohexane (1) -> methylcyclopentane (1) in excellent agreement with the result, 1150 cal., obtained by Glasebrook and Lovell (4) from their direct equilibrium measurements. IV.…”

“…Thus with additional spatial protection to the ethylene group the olefins becomes progressively less unstable with reference to the parent paraffin hydrocarbons. Methylcyclopentane (1) 940,360 -33,730 59.3 -136. The saturated hydrocarbons containing fiveor six-membered rings occupy free-energy levels somewhat intermediate between the corresponding aliphatic paraffins and olefins.…”

“…The third law of thermodynamics in conjunction with the fundamental equation AF = AH -TAS (1) has provided the only generally applicable, independent method for obtaining free-energy data for the hydrocarbons containing six or more carbon atoms. Statistical calculations of entropy and free energy have yielded extremely accurate values for many of the simpler molecules.…”

“…Statistical calculations of entropy and free energy have yielded extremely accurate values for many of the simpler molecules. At the present time, however, such calculations are just being developed 1 Presented at the Symposium on Fundamental Chemical Thermodynamics of Hydrocarbons and their Derivatives, which was held at the Ninety-ninth Meeting of the American Chemical Society, in Cincinnati, Ohio, April 10, 1940, under the auspices of the Division of Petroleum Chemistry of the American Chemical Society. for some of the more complicated molecules here involved and this development process is dependent to a high degree on accurate entropy de-terminations made by the third-law method (15).…”