Index of content:
Volume 22, Issue 8, 01 August 1954
22(1954); http://dx.doi.org/10.1063/1.1740382View Description Hide Description
Measurements of viscosity,ultrasonic absorption, and velocity were made in a group of associated organic liquids, known as the diols. Included in the measurements were ethanediol, two isomers of propanediol, and three isomers of butanediol. In these liquids the values of absorption ranged from 1.66 to 2.20 times that value calculated from Stokes formula. The effect of the structural differences indicated the following, when the addition of CH2 groups was considered, (1) an increase in shear viscosity, (2) an increase in adiabatic compressibility, (βad), and (3) an increase in the ratio of αobs/αcalc. Effects caused by isomeric changes were (1) an increase in βad and (2) an increase in αobs/αcalc as the (OH) groups were brought closer together. It was concluded that a relationship existed between the ratio of αobs/αcalc and βad.
Measurement of absorption vs temperature in ethanediol over a viscosity range of 24:1 indicated that the difference in activation energy of shear and compressional viscosity could be no greater than 0.1 percent.
22(1954); http://dx.doi.org/10.1063/1.1740383View Description Hide Description
Thermal diffusion measurements have been made to 10 000 atmospheres at 40°C and 78°C pressure for the systems.
22(1954); http://dx.doi.org/10.1063/1.1740384View Description Hide Description
Thermal diffusion measurements have been made on a series of binary mixtures of normal paraffin hydrocarbons with tetrachloroethane over a range of temperatures from 5‐55°C. The results are analyzed in terms of a previously published theory. The size of hole left by the hydrocarbon seems independent of chain length up to an eight or nine carbon chain. If the moving segment is assumed to be eight carbon atoms long, the size of hole left by the segment is independent of total chain length.
22(1954); http://dx.doi.org/10.1063/1.1740385View Description Hide Description
Thermal diffusion measurements have been made for binary mixtures of CS2 and the five isomeric hexanes at atmospheric pressure and under pressure to 10 000 atmospheres. The data, measured in two different types of apparatus, are consistent. The results indicate that the further the deviation from spherical symmetry, the larger the value of the steric correction factor ψ. Thus, for mixtures of molecules of the same size and cohesive energy, the more spherically symmetrical will concentrate at the cold wall.
Vibrational Spectra and Calculated Thermodynamic Properties of Ethyl Chloride and 1,1‐Dichloroethane22(1954); http://dx.doi.org/10.1063/1.1740386View Description Hide Description
The infrared absorption spectra of H3C–CH2Cl and H3C–CHCl2 in the gaseous and liquid states have been obtained in the region from 2 to 38μ with the aid of LiF, NaCl, KBr, and KRS‐5 prisms. The Raman spectra of the liquids have been photographed with a 3‐prism glass spectrograph of linear dispersion 15 A/mm at 4358A. Relative intensities and depolarization ratios have been measured for most of the Raman bands. Complete assignments of fundamental vibrational frequencies have been made, the spectra have been interpreted in detail, and thermodynamic functions have been calculated for the compounds in the gaseous state.
22(1954); http://dx.doi.org/10.1063/1.1740387View Description Hide Description
Based upon a united atom model, it has been shown that the ionization potentials of complex molecules can be calculated from molecular orbitals formed from group or united atom orbitals. With this method ionization potentials have been calculated for a large number of paraffins, olefins, aromatics, alkyl halides, amines, and oxygen compounds. With a few exceptions, the agreement of calculated and measured values is excellent.
22(1954); http://dx.doi.org/10.1063/1.1740388View Description Hide Description
Studies on the ``hot atom'' reactions resulting from slow neutron irradiation of methyl iodide have been carried out. The results show that concentration of free iodine below 0.007 percent in CH3I during irradiation has a great influence on the distribution of the 25‐min I128 between CH3I, CH2I2, and I2.
Comparison of experiments at temperatures below —55°C with carefully purified CH3I indicates that the yield of the reactions in pure CH3I is: CH3I, 44.4 percent; CH2I2, 11.2 percent; and I2, 44.2 percent.
The influence of the temperature on this reaction shows that no change in yield has been found at the shift between liquid and solid state. Co60 rays at a rate of 2 roentgen per min at the side of sampling during neutron irradiation, do not change the distribution of the radioactive I128 between the compounds.
22(1954); http://dx.doi.org/10.1063/1.1740389View Description Hide Description
A recent solution of the Debye‐Hückel equations for a single polarized electrode obtained by Breyer and Gutmann is revised to yield an exact solution of this problem. This solution is compared with an earlier result of H. Müller derived from different initial equations and the solutions are shown to be identical.
The present solution applies only to the diffuse part of the double layer of electrolyte theory and yields the following expression for the mean local potential within the material as a function of the distance x from a polarized anodewhere LD is the Debye length and V 0 the potential applied between electrode and charge‐containing material.
22(1954); http://dx.doi.org/10.1063/1.1740390View Description Hide Description
Exact solutions of the static Debye‐Hückel space‐charge equations for one and for two blocking electrodes are compared analytically and graphically. It is found that the simpler one‐electrode solution may be employed to characterize the diffuse double layer with high accuracy in most experimental situations in place of the less tractable two‐electrode solution which involves Jacobian clliptic functions. Some consequences of the strong nonlinear voltage dependence of the exact solutions are considered and the application of the solutions to physical situations is discussed.
22(1954); http://dx.doi.org/10.1063/1.1740391View Description Hide Description
Crystals of KH2PO4, NH4H2PO4, KH2AsO4, and NH4H2AsO4 were examined in the 1—25 micron region. Data were obtained at room temperature for all four crystals, and in addition the spectra of the potassium compounds were examined below their Curie points. In order to avoid the use of thin crystal cuts required for absorption measurements, an optical system was designed which permitted recording of reflection spectra. At the low temperature an increase in the number of bands was observed, and the phosphate and arsenate spectra seemed displaced to higher frequencies. The transition from hydrogen bonding prevailing at room temperature to hydroxyl bonding below the Curie points is considered likely.
22(1954); http://dx.doi.org/10.1063/1.1740392View Description Hide Description
Alternating current impedance measurements on samples of silver bromide with silver and with goldelectrodes show the presence of polarizationeffects. These effects appear as a capacitive component of the impedance and a slight dependence of the resistance on the frequency of the measurement, and their dependence on temperature, frequency, pressure, voltage, and impurity content has been investigated. A macroscopic theory is developed to describe the motion of the mobile charge carriers (ionic defects) which exist in AgBr at elevated temperatures. The general equations contain the effects of conduction and diffusion currents, space charge, and formation and recombination. Since these equations are nonlinear, an approximation procedure is developed, which is valid for small values of the applied voltage. The results of the theory with appropriate boundary conditions give semiquantitative agreement with the temperature and frequency dependence of the observed results and afford a good qualitative description of all of the observed effects. It is concluded that Frenkel defects are responsible for the polarizationeffects and that the formation and recombination rate is smaller than might at first be expected.
22(1954); http://dx.doi.org/10.1063/1.1740393View Description Hide Description
The electronic states and the molecular constants of the ground and lower excited states of the CH radical are calculated by the Heitler‐London method and the LCAO‐SCF method. In the former, s 2 p 2, sp 3, and p 4 configurations of the carbon atom are taken into account for the wave function, and in the latter LCAO‐SCF MOs are calculated for the ground and lower excited states. The interactions between all electrons are considered, but the orthogonal relationship between the 1s orbitals of carbon and hydrogen is assumed. As much as possible, the energy integrals were computed from SCF AOs. The results are in general agreement with the observations and Mulliken's prediction. It is concluded that without configuration interaction no satisfactory LCAO‐SCF calculation can be made to determine the ground state of the radical as well as of the electronic levels of the carbon atom.
22(1954); http://dx.doi.org/10.1063/1.1740394View Description Hide Description
If a molecule is produced in a medium containing molecules able to react with it, its instantaneous reactivity is a function of the time since its formation. At very short times the reactivity is determined by the conventional ``true'' rate constantk, which is the product of the rate constant for encounters and the probability of reaction during an encounter. At long times (10—9 sec or greater in many liquids), the reactivity falls to a value determined by the ``long‐time'' rate constantk′. The constants k and k′ differ by the factor 1 — β′, where β′ is the probability that a specific pair of molecules separating from a nonreactive encounter will ultimately react with each other. If β′ is small either because there is little chance of reaction per encounter (activation control), or because there is little chance the specific pair will undergo a subsequent encounter (as in gas phase), the two rate constants are virtually identical and conventional kinetics apply.
Equations are developed for the time dependence of the reactivity of a molecule in such a system, and a model is suggested for evaluating the necessary parameters in terms of the relative diffusion coefficient, the encounter diameter, and the root‐mean‐square displacement distance during diffusion. Application of available kinetic data indicates that diffusive displacements in liquids are of the order of a molecular diameter and take place with a frequency of the order of 1011 sec—1.
In the quenching of fluorescence and other processes where reactive molecules are produced singly, experimental measurements have given the ``long‐time'' rate constant,k′. When reactive molecules are produced in pairs, the recombination process in a thermal equilibrium is described by the ``true'' rate constant,k; but k′ has been obtained from all rate measurements on the recombination of pairs produced photochemically. Experiments are suggested for obtaining information on systems during the short time in which the apparent rate constant in changing.
22(1954); http://dx.doi.org/10.1063/1.1740395View Description Hide Description
Although much attention has been given to the physics of a microwaveglow discharge, substantially less information is available regarding the chemical effects upon a gas undergoing such excitation. We have studied the chemical effects of a 2450‐Mc/sec glow discharge on several gases and have made quantitative measurements on a few simple molecular systems, e.g., N2, H2, O2, air, CH4. A fundamental relationship has been found to exist between the yield in simple chemical systems and the controllable variables of electric field strength, contact time, and pressure. Analytical expressions for these relationships have been obtained.
22(1954); http://dx.doi.org/10.1063/1.1740396View Description Hide Description
A trial wave function consisting of a linear combination of 1S orbitals centered on the nuclei and on a point half‐way between them was used in a variational treatment of H2 +. A one‐electron three‐center integral with nonequal charges which arises in the course of this treatment was evaluated. The effective nuclear charges for minimum energy were found approximately by calculating energies for a range of values of the separated atom charge and of the united atom charge. The lowest energy calculated, —0.5969 au, occurred where both effective nuclear charges are equal at 1.25. The energy value should be compared with —0.6031 au, the exact value, and with —0.6001 au obtained by hybridizing 1S and 2Pz orbitals on the separated nuclei. The ratio of the united atom coefficient to separated atom coefficient was found to be 0.3501 for the energy value mentioned.
22(1954); http://dx.doi.org/10.1063/1.1740397View Description Hide Description
The ferrous sulfate radiation dosimeter (herein called the Fricke dosimeter) has been recalibrated by a calorimetric method in which assumptions regarding energy absorbed in the glass and the heat capacity of the calorimeter have been eliminated. The 100‐ev yield, G(Fe++→Fe+++), is 15.8±0.3 for Co60gamma radiation in agreement with the Hochanadel‐Ghormley value. The result is compared with other G values reported in the literature and it is recommended that the low value be adopted for Co60gamma radiation and for electrons in the 1—2 Mev range.
22(1954); http://dx.doi.org/10.1063/1.1740398View Description Hide Description
High‐temperature x‐ray diffraction patterns of germanium plus germanium oxide GeO2 between 750° and 1400°C, showed that germanium monoxide GeO is not a stable compound. At elevated temperatures germanium can dissolve up to 60 atom percent of oxygen. The oxygen causes first a slight expansion and then a contraction of the Ge lattice. At 850° and 930°C, the x‐ray pattern of a germanium‐oxygen compound, consisting of equimolecular quantities of germanium and oxygen, showed only the germanium pattern. At 1000° and higher (above the melting point of pure germanium, 965°C), the germanium pattern disappears, and liquid‐like structure is visible, though the sample is still solid (melting point 1430°C). When the temperature is lowered again to 930°C, the germanium pattern reappears. The electrical resistivity of the Ge and GeO2 mixture shows a sharp break at 970°C. In the germanium‐oxygen compound we thus have a disordering of the germanium lattice above the melting point of pure germanium.
22(1954); http://dx.doi.org/10.1063/1.1740400View Description Hide Description
Some further lines in the microwave spectrum of KCl have been observed at frequencies predicted by the rotational constants given by recent molecular beam work. Measurements have been made on the Stark patterns of the J=2→3, v=0 line of K39Cl35 and the J=1→2, v=0 line of Na23Cl35. The dipole moments of these molecules have been determined to be 10.1±0.2 Debye units for KCl and 8.5±0.2 Debye units for NaCl. The KCl value is in fair agreement with the results of molecular beam investigations.
22(1954); http://dx.doi.org/10.1063/1.1740401View Description Hide Description
Lines in the rotational spectrum of PH3, indentifiable with the rotation of the molecules in the first excited states of the frequencies ν2 and ν4, allow an independent test to be made of the Coriolis interaction between these states as calculated from the vibrational‐rotational band spectrum. It is shown that the B values observed from the rotational spectrum for these states are consistent with those obtained from the information derivable from the vibrational‐rotational spectrum.