Index of content:
Volume 22, Issue 7, 01 July 1954
22(1954); http://dx.doi.org/10.1063/1.1740321View Description Hide Description
Electrical measurements on dicobalt decamine‐μ‐peroxy complex (Vortmann's salt) are described. The current formulation contained CoIII and CoIV in crystallographically equivalent positions and hence it was thought that the complex might be an intrinsic semiconductor. An apparent dielectric constantK of 106 was found to be due to chemical polarization caused by traced of acid on the material. It is concluded on the basis of conductivity measurements that the material is not an intrinsic semiconductor.
22(1954); http://dx.doi.org/10.1063/1.1740322View Description Hide Description
The possibility of several complex compounds being intrinsic semiconductors is discussed in the light of experimental work presented in this paper and in Part 1. It is concluded that complexes containing metal atoms in different oxidation states in crystallographically equivalent positions are capable of acting as intrinsic semiconductors. Additional support is given to the alternative structure of Vortmann's salt proposed by Brimn.
22(1954); http://dx.doi.org/10.1063/1.1740323View Description Hide Description
A theory of thermal diffusion in liquids is presented which involves: (1) a molecular interpretation due to Denbigh of the results of the thermodynamics of irreversible processes in terms of regular solution theory; (2) a correction for differences in shape and size of the molecules.
Thermal diffusion measurements have been made to 10 000 atmospheres pressure on a series of binary mixtures in a single stage system. The results indicate that the theory is satisfactory.
22(1954); http://dx.doi.org/10.1063/1.1740324View Description Hide Description
A single‐stage two‐cell apparatus for measuring thermal diffusion in liquid mixtures has been developed. Thermal‐diffusion measurements are presented for a series of binary mixtures of molecules of simple symmetry over a range of temperature from 5°—55°C. The theory presented in a previous paper applies quite satisfactorily. The results indicate that the proposed measure of the cohesive energygives reasonably quantitative results.
22(1954); http://dx.doi.org/10.1063/1.1740325View Description Hide Description
New data are presented on the NH group stretching frequency of pyrrole in dilute and concentrated solutions in fourteen different solvents and in several solvent mixtures. It is shown that in nonpolar solvents ν(NH) of pyrrole obeys the Kirkwood‐Bauer relationship, δν/ν=C(D—1)/(2D+1), where C is a constant, and D is the solventdielectric constant. Furthermore, it is shown that C is only slightly affected as ν(HCl) of hydrochloric acid, ν(OD) of methanol‐d, or ν(OH) of methanol, ethanol, propanol, or phenol is substituted for the ν(NH) of pyrrole. The deviations from the Kirkwood‐Bauer relationship produced by polar solvents and aromatic hydrocarbon solvents are analyzed in terms of hydrogen bonding and the formation of molecular complexes. The effect of solvent upon band intensity is also briefly examined. A classification of types of OH and NH solution frequencies is suggested.
Evaluation of Some Electron Repulsion Integrals Needed in Molecular Quantum Mechanics. A Method of Calculation of Two Electron Multi‐Center Repulsion Integrals without the Use of the Neumann Expansion22(1954); http://dx.doi.org/10.1063/1.1740326View Description Hide Description
Consideration has been given to two of the electronic repulsion integrals arising in the quantum‐mechanical energy calculation of the triatomic hydrogen molecular complex when no restrictions are placed on the effective nuclear charges of the composite atomic orbitals. The formulation of the integrals is first developed on a general basis and then restricted to the H3 molecule. The possibility of extension of the mathematical processes to similar electron interaction integrals in more complex molecules is pointed out. The integration formulas are given as rapidly converging series.
22(1954); http://dx.doi.org/10.1063/1.1740327View Description Hide Description
Most molecular quantum‐mechanical studies of today make use of eigenfunctions composed of atomic orbitals. Such eigenfunctions give rise to difficult multicenter integrals which are usually evaluated by approximate methods. A study of the accuracy of such methods and of their derived results has long been desirable. Certain approximations for three‐center nuclear attraction integrals are here examined.
Complete sample calculations are made with the approximate integral values for the triatomic activated complex molecule, H3. The use of the Mulliken approximate evaluation of integrals in the Heitler‐London treatment for H3 gives a binding energy 7.6 kcal/mole less than does the use of exact integrals. On modifying the Heitler‐London treatment by inclusion of screening constants for the outer and central atomic orbitals the Mulliken type approximate integrals gave for a trial calculation a binding energy 5.3 kcal/mole better than the best previous determination. This trial calculation (using the parametric values R = 1.8, Z 0 = 1, Zm = 1.08) while the best of several tried is not likely the best that can be found. However, the binding energy of 72.7 kcal/mole calculated is 26 kcal/mole better than the Heitler‐London value (53.4 kcal/mole) and 5 kcal/mole better than the Wang‐like covalent‐bond‐plus‐ionic‐terms determination using a single screening parameter.
The cited trial calculation indicates that similar determinations now in progress using exact integral evaluations will give a substantial increase in the calculated binding energy of H3. This would be, for this simplest polyatomic molecule, the first major advance since 1936. That the approximate calculation is essentially correct is substantiated by the increase in binding energy obtained with the proper screening constant variation for the diatomic molecule. In the H2 case Wang obtained an improvement from 72.4 kcal/mole to 86.7 kcal/mole over the best covalent‐plus‐ionic term calculations.
22(1954); http://dx.doi.org/10.1063/1.1740328View Description Hide Description
We have calculated the rotational energy transition probability upon collision using approximate results from a previous distorted wave calculation. For heavy homonuclear diatomic molecules, i.e. molecules with molecular weight >20, the mean transition probability is approximated by ½(d 0/r 0)2, where d 0 is the internuclear distance and r 0 the kinetic collision diameter. This expression is in agreement with relaxation times as calculated from shock wave data.
22(1954); http://dx.doi.org/10.1063/1.1740329View Description Hide Description
Infrared spectra of 1,1‐dimethylhydrazine between 700 and 1600 cm—1 for the gas phase and between 700 and 3500 cm—1 for the liquid phase and of trimethylhydrazine between 700 and 3500 cm—1 for the gas and liquid phases are reported along with the Raman spectra of the two compounds. Frequency assignments are given for both compounds.
22(1954); http://dx.doi.org/10.1063/1.1740330View Description Hide Description
The infrared spectra of thionyl chloride and sulfuryl chloride have been investigated from 400 cm—1 to to 5000 cm—1 with a prismspectrometer. Three of the fundamentals of SOCl2 have been found and four for SO2Cl2. They and the various additional bands have been assigned to their appropriate symmetry species assuming SOCl2 has C8 symmetry and SO2Cl2 has C 2v symmetry.
22(1954); http://dx.doi.org/10.1063/1.1740331View Description Hide Description
Spinels of the , system have been made by reduction of the corresponding sesquioxide solid solution at 1180°C, 1100°C and 950°C and the lattice parameters determined at room temperature. The solutions of approximately stoichiometric composition have lattice parameters which vary with x in a nonlinear manner from 8.396±0.002A at x=0 to 8.376±0.002A at x=2. The four essentially linear segments comprising the total curve are interpreted as follows: from x=0 to x=0.3 the structure is completely inversed; from x=1.28 to x=2.0 it is completely normal; between these regions reversion from the inversed to the normal form occurs in two successive stages. Oxygen‐rich spinels crystallized at 950°C show the same general variations of parameter but the region of complete inversion extends to approximately x=0.6.
22(1954); http://dx.doi.org/10.1063/1.1740332View Description Hide Description
The infrared spectrum of gaseous bromotrifluoroethylene F2C:CFBr has been investigated in the range 2—52μ. The assignment of fundamentals parallels that for chlorotrifluoroethylene very closely. The planar vibrational frequencies in cm—1 are 1783(ν CC), 1330(ν CF), 1203(ν CF), 1027(ν CF), 659(ν CBr), 510(δ CF2), 370(δ CFBr), 311(ρ CF2), 160(ρ CFBr), while the out‐of‐plane modes are assigned 538(β CF2), 355(β CFBr), and 150(τ). A table of thermodynamic functions for the ideal gas is given.
22(1954); http://dx.doi.org/10.1063/1.1740333View Description Hide Description
The molecules KClFeCl2 and KBrFeBr2 have rotational magnetic moments much larger than those found in other heavy molecules with large moments of inertia. The maximum magnetic moment of the state of most probable J at a temperature of 935°K is about 72 nuclear magnetons for the first of the molecules and about 50 nuclear magnetons for the second of these molecules.
22(1954); http://dx.doi.org/10.1063/1.1740334View Description Hide Description
The fluorescence efficiency of biacetyl vapor when excited by radiation of wavelength 4358A is independent of the number of quanta absorbed per cubic centimeter per second, almost if not quite independent of biacetyl pressure, and decreases with increase in temperature but there seems to be a transition from one type of variation with temperature to another between 60° and 100°. Oxygen quenches the fluorescence strongly, and isobutylene quenches the fluorescence little or not at all.
The marked difference in fluorescence behavior of biacetyl when excited by 4358A radiation from that when excited by 3660A radiation as pointed out by previous authors makes desirable an attempt to correlate fluorescence with photochemical behavior. Some suggestions are made with regard to mechanism.
22(1954); http://dx.doi.org/10.1063/1.1740335View Description Hide Description
Pure quadrupole resonances of bromine or iodine nuclei have been observed in paradibromo‐ and paradiiodo‐benzene; the tetrabromides of carbon,silicon,germanium and tin;germanium and tin tetraiodides; sodium,potassium, and cesium bromates; antimony tribromide and iodide; and cyanogen bromide. For most of these compounds, measurements were made at room temperature and at liquid nitrogen temperature. The results are correlated with chemical bonding and crystal structure data.
22(1954); http://dx.doi.org/10.1063/1.1740336View Description Hide Description
A rate equation is derived for heterogeneous nucleation of crystals from the vapor on the basis of an adsorption, surface diffusion, and statistical fluctuation mechanism. It should be emphasized that the term surface diffusion as used in this development does not imply the existence of a gradient. Rather it refers to random movement of absorbed atoms on the subtrate surface. It is shown that this mechanism results in a rate at least 102 to 103 times greater than that calculated on the basis of direct addition of atoms to the critical nucleus from the vapor phase. The equation describes the temperature dependence of existing critical supersaturation data for heterogeneous nucleation. Analysis of the existing data by this treatment permits an evaluation of the standard free energy of adsorption. Particular attention is given to heterogeneous nucleation from atomic beams.
22(1954); http://dx.doi.org/10.1063/1.1740337View Description Hide Description
The second differential ionization efficiency curves for a number of simple molecule‐ions have been recorded using a new technique of measurement. A close correlation can be drawn between the results and spectroscopic data, confirming in most respects the interpretation of ionization efficiencies made in Part III. It proves possible to detect the presence of upper ionic states at energies corresponding to extreme ultraviolet radiation. The factors which affect line shape in optical spectra are shown to apply also to the second differential ionization efficiency curves, which are termed electron spectra. It is shown that the ionization efficiency curves for fragment ions can also be interpreted in a similar manner, and the types of electron spectra to be expected for different kinds of dissociation processes are discussed.
The Effect of Ring Substituents on the Isotope Effects in Reactions of Carbonyl‐C14 Esters and Ketones22(1954); http://dx.doi.org/10.1063/1.1740338View Description Hide Description
The variations of the isotope fractionation factor k 14/k 12 with changes in ring substituents, reaction temperature, solvent, concentration, and the alcohol group have been studied for the saponification of ethyl benzoates (α‐carbon‐14). The variations of the k 14/k 12 ratio with changes in temperature and ring substituents have been studied for the formation of the 2,4‐dinitrophenylhydrazones of acetophenones (α‐carbon‐14).
22(1954); http://dx.doi.org/10.1063/1.1740339View Description Hide Description
The infrared spectra of formamide in the vapour and liquid states, and in solutions in CHCl3, CCl4, CH3CN, H2O, and D2O, and of sodium formamide and formamide hydrochloride were observed between 650 cm—1 and 3800 cm—1. The effect of association on the bands was examined, where possible, in solution and in the vapor state. These infrared results were taken in conjunction with the available Raman data and an assignment of the frequencies to the fundamental modes of vibration of the molecule has been made. Thermodynamic functions have been calculated.
The Application of the Debye‐Hückel Theory to Polyions. Part I. The Range of Applicability of the Debye Limiting Law22(1954); http://dx.doi.org/10.1063/1.1740340View Description Hide Description
The Debye limiting law has been used to deduce an expression for the electrical work which must be done to build up a polyion from the corresponding single ions in extremely dilute solutions containing various (appreciable) concentrations of 1 — 1 electrolyte. The case of an infinite straight rigid polyion having charges at equal intervals along its length was treated in greater detail, and a corrected expression was obtained for the above‐mentioned electrical work, which makes allowance for the finite size of the polyion charges and takes some account of the steric effects due to the remainder of the polyion molecule. The error due to the high electric potential ψ surrounding such a polyion which invalidates the Debye approximation of replacing sinh (εψ/kT) by εψ/kT was evaluated by numerical integration of the Poisson‐Boltzmann equation. The integration was started at a considerable distance from the polyion on the assumption of cylindrical symmetry and continued at closer distances on the assumption of spherical symmetry surrounding each polyion charge. The results obtained indicated that the error involved in using the simple Debye limiting law formula would seldom be more than a few percent, provided the concentration of the 1 — 1 electrolyte was rather low (not more than about N/100).