Volume 11, Issue 8, 01 August 1943
Index of content:
11(1943); http://dx.doi.org/10.1063/1.1723855View Description Hide Description
The energy of the molecules of a liquid in their equilibrium positions and the frequency of vibration about those positions are expressed in terms of a parameter a, the average distance between the molecules. This follows from a formulation of an average potential or spherical symmetry from an assumed force field between pairs of molecules. The ordinary thermodynamic quantities are calculated from the resultant harmonic oscillator‐partition function. Order‐disorder effects are neglected.
11(1943); http://dx.doi.org/10.1063/1.1723856View Description Hide Description
Measurements of the velocity and absorption of supersonic waves in carbon tetrafluoride were made over a range of pressures for each of two different frequencies. From the dispersion and absorption curves so obtained, the specific heat for equilibrium conditions, that portion of the specific heat due to intra‐molecular vibrations, and the mean lifetime of a quantum of vibrational energy were calculated.
11(1943); http://dx.doi.org/10.1063/1.1723857View Description Hide Description
Monochromatic x‐ray diffraction patterns of liquid CCl4 at 25°C and at −20°C have been analyzed to obtain radial electron density distribution curves. These curves show discrete peaks corresponding to distances between atoms in a molecule (1.7A and 2.9A at −20°C; 1.74A and 2.92A at 25°C), as well as other peaks (3.6A, 4.1A, and 6.4A at −20°C; 4.0A and 6.3A at 25°C) which are not discrete and which represent distances between atoms in different molecules.
11(1943); http://dx.doi.org/10.1063/1.1723858View Description Hide Description
Here are recorded data on the magnetic susceptibilities of potassium and of cesium dissolved in liquid ammonia at 240°K and 220°K. Also included are a few data on calcium and barium. These solutions throughout the entire range of concentrations were regarded as representing an electron gas. Such systems would permit the distributions of the magnetic moments of the electrons to be followed continuously from the degenerate region of the Fermi‐Dirac statistics to those distributions where the quantum and classical statistics are indistinguishable. The general features of the magnetic behavior of a free electron gas were recognized, overlaid, however, by interactions characteristic of the environment of the electrons in the solutions. In the light of the magnetic susceptibilities as well as of other properties, a description is proposed for the structure of the solutions with special reference to the conduction electrons.Barium was found to dissociate into two electrons per gram atom and it is inferred that calcium dissociated likewise, but much greater dilutions would be required for a satisfactory demonstration. A method of considerable sensitivity and accuracy has been developed for measuring the magnetic susceptibilities of substances at low temperatures.
11(1943); http://dx.doi.org/10.1063/1.1723859View Description Hide Description
The infra‐red spectrum of trideuteronitromethane has been studied in the range 3–25μ, and the Raman spectrum has been analyzed. From this data and that obtained by Wells and Wilson on nitromethane it has been possible to determine all the fundamental frequencies except that of the torsion about the C–N bond, and to carry out a normal coordinate treatment from which a potential function fitting the observed frequencies of nitromethane and trideuteronitromethane within 2 percent has been obtained.
11(1943); http://dx.doi.org/10.1063/1.1723860View Description Hide Description
The infra‐red spectrum of cyclobutane in the range 2 to 25μ has been obtained, together with the Raman spectrum of the same material. Analysis of these spectra, together with a normal coordinate treatment of the problem, has led to a tentative assignment of the fundamentals which explains all features of the observed spectra. Butene‐1 has been identified as a product of the liquid phase photolysis of cyclopentanone.
11(1943); http://dx.doi.org/10.1063/1.1723861View Description Hide Description
The various elementary steps of vinyl polymerization reactions are discussed. Activation is considered to occur by collision of an unactivated monomer either with another monomer, a catalyst, a solvent, or a polymer molecule. It is further taken into account that certain types of active nuclei can be more easily deactivated than others. Two steps of propagation are considered: normal chain growth and chain transfer. Termination of growing chains is assumed to be possible either by collision with another growing chain, with an activated monomer, with a molecule of the catalyst, or with certain chain breaking impurities. Using the assumption that for a certain period of the reaction a steady state of activated centers is maintained, equations are derived for the initial over‐all rate of the reaction and for the number average polymerization degree. These equations are compared with experiments which have been carried out on the polymerization of styrene at various temperatures, monomer concentrations, and catalyst concentrations. Comparison between theory and experiments shows that in first approximation, the initial over‐all rate of the reaction and the initial number average polymerization degree can be represented by the derived equations.
11(1943); http://dx.doi.org/10.1063/1.1723862View Description Hide Description
The (isothermal) Young's modulus of idealrubber is determined by statistical methods. The macro‐state of a chain‐molecule is here defined in terms of its length and not in terms of the distance between the ends of the chain. Section 1 deals with thermodynamical results holding for ideal rubber and in Section 2 the treatment based on ends‐separation of the molecule‐chain is described. Section 3 treats the problem on the basis of the length of the molecule‐chain.