Index of content:
Volume 20, Issue 10, 01 October 1952
20(1952); http://dx.doi.org/10.1063/1.1700203View Description Hide Description
Recent experiments have demonstrated the feasibility of observing nuclear electric quadrupoleinteractions of widely varying magnitudes in solids. While these effects can often be observed in powdered samples, the most complete information is obtainable from the Zeeman pattern of a single crystal. To facilitate interpretation of these experiments, the nuclear spinenergy levels are derived for different relative magnitudes of quadrupoleinteraction and external magnetic field. Besides the knowledge of the gradient of the electric fieldtensor, in principle, low frequency molecular rotation should be detectable by means of the quadrupole spectra.
20(1952); http://dx.doi.org/10.1063/1.1700204View Description Hide Description
The transfer of energy from one species of hydrocarbon to another has been observed. The conditions under which such transfer occurs indicate that one aromatic hydrocarbon may be adsorbed onto crystals of the other forming a surface complex with a binding energy of a few hundred calories. Transfer of energy occurs readily between the components of this complex but not between molecules of different hydrocarbons when both are in solution. However, evidence for resonance transfer of energy between pairs of molecules of the same substance when both are in solid solution has been found.
20(1952); http://dx.doi.org/10.1063/1.1700205View Description Hide Description
The physical properties of n‐butforane C4F10 were determined and also these mixtures of it with n‐butane, C4H10. The properties of these two‐component systems parallel very closely the system previously reported, n‐pentforane and n‐pentane. The necessity of a concept such as that of ``interpenetration'' is confirmed.
20(1952); http://dx.doi.org/10.1063/1.1700206View Description Hide Description
The linear relation between the logarithm of the solubility of a solid nonelectrolyte and the logarithm of the absolute temperature, recently set forth by one of us, makes possible a rather accurate calculation of the partial molal entropy of transfer of the solute from solid to saturated solution. By subtracting from this the calculated entropy of fusion of the solid, one obtains the entropy of transfer from pure liquid to solution. This is several entropy units in excess of the ideal entropy in the case of solutions with high activity coefficients, but this difference is satisfactorily accounted for by the entropy involved in the expansion which accompanies the formation of such solutions under constant pressure. The entropy of mixing at constant volume seems to conform closely to the ideal (or Flory‐Huggins) entropy.
20(1952); http://dx.doi.org/10.1063/1.1700207View Description Hide Description
The fundamental thermodynamics and kinetics of hydrogen overvoltage are re‐examined and improved. A precise definition of the transfer coefficient is given, the significance of the free energy of activation is discussed, and additional theoretical support is given for the interpretation of hydrogen overvoltage as being due to the establishment of reversible atomic hydrogen electrodes.
20(1952); http://dx.doi.org/10.1063/1.1700208View Description Hide Description
The structure of bromoform has been evaluated entirely from microwave spectroscopy. The B 0 values in Mc/s of the isotopic species studied are: 1247.61±0.025 for CHBr3 79; 1217.30±0.025 for CHBr3 81; 1239.45±0.025 for CDBr3 79; 1209.51±0.025 for CDBr3 81. These constants yield the structure as follows: d CH=1.07A±0.01A, d CBr=1.930A±0.003A, angle BrCBr=110°48′±16′.
20(1952); http://dx.doi.org/10.1063/1.1700209View Description Hide Description
A general theoretical method for evaluating the effect on thermodynamic properties of cooperative orientation in solutions is developed. The theory is applied to the systems methanol+benzene, methanol carbon tetrachloride, and chloroform+ethanol. Theoretical curves for excess free energy of mixing, heat of mixing, and excess entropy of mixing as functions of composition are presented and are in reasonable quantitative agreement with experimental values for the first two systems and qualitatively similar to the experimental curves for the third. It is concluded that the method provides a useful approach to the theory of solutions of associated liquids in general.
20(1952); http://dx.doi.org/10.1063/1.1700210View Description Hide Description
A regularity exists between the heat of formation of alkali and alkaline earth oxysalts and the acidity and basicity of the oxides involved. The more basic an alkali or an alkaline earth oxide, the larger is the exothermic heat of formation of its oxysalts from the component oxides. Likewise, the more acidic the nonmetal oxide, the larger is the exothermic heat of formation of its salts from the component oxides. Although this is expectable in a general way, the regularity and consistency of these rules are rather surprising.
The exothermic heat of formation from the oxides of different oxysalts of the same metal increases when the nonmetal changes through the sequences: B, C, N, and Si, P, S, Cl. This is explained in light of the increasing covalent character (or increasing polarization) of the oxygen‐nonmetal bonds through the same series of elements.
The exothermic heat of formation of polymerized oxysalts from the component oxides (borates, silicates, phosphates, pyrosulfates) is larger per equivalent than for the corresponding simple oxysalts. This is qualitatively explained as a result of the oxygen‐nonmetal bond being less polarized or more ionic in a polymerized salt than in the nonpolymerized salt with the same central atom in the oxyanion.
The heat of salt formation per equivalent increases numerically when the metal changes from Li to Cs, or from Mg to Ra. This is related to the increase of the crystal energy of the corresponding metal oxides.
20(1952); http://dx.doi.org/10.1063/1.1700211View Description Hide Description
The free volume theory of the liquid state is extended to multicomponent mixtures by using the method of moments in the treatment of the order‐disorder problem. Retention of only the first moment yields an approximation to the partition function which has recently been studied by Prigogine and Garikian and by Prigogine and Mathot. An approximation equivalent to retaining the third moment is given, and the calculation of the thermodynamic functions from the first moment approximation is discussed.
20(1952); http://dx.doi.org/10.1063/1.1700212View Description Hide Description
The thermodynamic functionsCp 0, S 0, —(F 0—E 0 0)/T, and (H 0—E 0 0)/T of the six diatomic interhalogens, chlorine monofluoride, bromine monofluoride, iodine monofluoride, bromine monochloride, iodine monochloride, and iodine monobromide, have been evaluated as a function of temperature from 298.16°K to 2000°K by the application of statistical methods. These results have been combined with newly evaluated properties of the fluorine, chlorine, bromine, and iodine atoms and molecules to yield the heats and free energies of dissociation and dissociation constants for the equilibria between the interhalogens and their molecular and atomic dissociation products. The calculations are based on available experimental spectroscopic constants with the exception of the anharmonicity term and internuclear distance for bromine chloride and of the internuclear distances in iodine fluoride and iodine bromide. These quantities are estimated empirically.
Spectroscopic Studies in the Near Ultraviolet of the Three Isomeric Dimethylbenzene Vapors. III. Fluorescence of Meta‐Dimethylbenzene20(1952); http://dx.doi.org/10.1063/1.1700213View Description Hide Description
Theoretical Considerations Concerning Hammett's Equation. III. σ‐Values for Pyridine and Other Aza‐Substituted Hydrocarbons20(1952); http://dx.doi.org/10.1063/1.1700214View Description Hide Description
Electron distributions in pyridine, pyrimidine, quinoline, isoquinoline, acridine, phenazine, and phenanthridine have been calculated by the LCAO MO method, and used to calculate Hammett's σ‐values for the different positions in these compounds. The values are compared with the experimental values available for pyridine, quinoline, and isoquinoline, and satisfactory agreement is obtained. Formulas are given for the calculation of σ‐values of similar compounds.
20(1952); http://dx.doi.org/10.1063/1.1700215View Description Hide Description
About 50 percent of the I128 atoms formed by the I127(n, γ)I128reaction in gaseous mixtures of 0.2 mm of iodine and 400 mm of methane enter combination as methyl iodide, whereas much less than 1 percent of iodine atoms produced simultaneously by the photochemicaldissociation of the iodine do so. By contrast, about 1 percent of the I128 formed by the I127(n, γ)I128reaction in gaseous mixtures of iodine and ethyl iodide enters organic combination.
The solubility of iodine in pure liquid methane is less than 10−10 m/1 but as much as 3×10−5 m/1 may be dissolved when air has been allowed to condense in the methane. In such solutions I128 from the I127(n, γ)I128reaction is able to enter organic combination as methyl iodide, ethyl iodide, and higher boiling material.
20(1952); http://dx.doi.org/10.1063/1.1700216View Description Hide Description
With the aid of approximate models for the intermolecular potential energy, the third virial coefficient Γ3 in the virial expansion for the osmotic pressure of a dilute polymer solution has been determined as a function of the second coefficient and one additional parameter obtainable from intrinsic viscosity or light scatteringmeasurements. The theory and experimental results agree in indicating that the ratio Γ3/Γ2 2 for most solutions is markedly less than the value of ⅝ given by the hard sphere molecular model proposed by others for the estimation of Γ3. The limitations are discussed under which light scattering may be used for evaluation of the virial coefficients.
20(1952); http://dx.doi.org/10.1063/1.1700217View Description Hide Description
Self‐diffusion coefficients in liquid mercury have been measured by the capillary technique and have been found to be in disagreement with the earlier calculated values of Haissinsky and Cottin. In view of the fact that the present data have been obtained by direct measurement and are also much more compatible with known viscosity data, it is concluded that the data of Haissinsky and Cottin are invalid. An examination of liquid self‐diffusion data in general has shown that the Stokes‐Einstein equation usually gives a much better correlation of self‐diffusion and viscosity coefficients than the Eyring equation.
20(1952); http://dx.doi.org/10.1063/1.1700218View Description Hide Description
The infrared and ultraviolet spectra of 15 alkyl nitrites were studied in the gaseous state. In the infrared, the O–N=O group is characterized by very strong absorption in the three regions 600, 800, and 1650 cm−1, corresponding to O–N=O bending, N–O stretching, and N=O stretching frequencies, respectively. The doubling of the characteristic frequencies and the temperature dependence of the bands of methyl nitrite are explained by rotational isomerism, which appears to be a general property of alkyl nitrites. The influence of the length, shape, and kind of the carbon chain on the frequencies and intensities of the characteristic bands has been studied. The intensity variation of the νN=O bands strongly suggests that the relative abundances of the two isomers vary widely from primary to secondary and tertiary nitrites, but depend only to a small extent upon the length and shape of the carbon chain. Application of this property to the diagnosis of primary, secondary, or tertiary alcohols is suggested.
The uv spectra consist essentially of two systems of diffuse bands (and not of one, as stated by previous workers), whose relative intensities vary in the same manner as the relative abundances of the two rotational isomers. The two systems of bands are accordingly assigned to these rotational isomers. This hypothesis has been checked by a study of the temperature dependence of the intensity of the bands.
Approximate Treatment of the Effect of Centrifugal Distortion on the Rotational Energy Levels of Asymmetric‐Rotor Molecules20(1952); http://dx.doi.org/10.1063/1.1700219View Description Hide Description
A first‐order treatment yields the relationfor the rotational energy W of a nonrigid asymmetric rotor. The A's are constants independent of the rotational quantum numbers (J, K −1, K +1) while W 0 is the rigid‐rotor energy. P z is the operator for the component of angular momentum along the axis of quantization. Formulas are given for 〈P z 2〉 and 〈P z 4〉, based on continued fractions, as well as expansions useful for nearly symmetric cases. As a special case, the corrections are derived for transitions between the components of asymmetry doublets.
20(1952); http://dx.doi.org/10.1063/1.1700220View Description Hide Description
20(1952); http://dx.doi.org/10.1063/1.1700221View Description Hide Description
Vibrational relaxation times in gases are calculated with the method of Zener using an exponential repulsion in a one‐dimensional model. The constants of the interaction potential are determined by fitting it to the data of Hirschfelder, et al. The great effect which some impurities have is accounted for either by their low mass and resultant high velocity or by ``near resonance'' transfers in which the vibrational quantum of the substratum is used partly to excite the vibration of the impurity, only the difference being transferred to translation. However, there are other impurities, the action of which cannot be explained in this manner. The theoretical values for the relaxation times are 10 to 30 times shorter than the experimental ones, which difference may be accounted for by the use of the one‐dimensional model. Macroscopic equations governing the more complex relaxation processes in polyatomic gases and gas mixtures are developed.
Semilocalized Orbitals. IV. Relationship of n‐Center Orbitals, Two‐Center Orbitals, and Bond Properties20(1952); http://dx.doi.org/10.1063/1.1700222View Description Hide Description
The relationship between n‐center orbitals, two‐center orbitals, and bond properties is discussed from the standpoint of atomic, molecular, and semilocalized orbital theory.
The necessary restrictions on the transformation from the more general n‐center to the two center orbitals is also discussed and a practical computational method for molecular problems is suggested.
The relationship of the atomic and molecular orbital theories of the excited electronic states of molecules is also investigated.