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1 Dec 1940

Volume 8, Issue 12, pp. 899-998


Ozone in Silent Electric Discharge

William H. Otto and Willard H. Bennett

J. Chem. Phys. 8, 899 (1940); http://dx.doi.org/10.1063/1.1750603 (5 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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Ozone is produced in silent discharges in air by collisions intermediate between ionizing energies and attaching energies, due to the dissociation of oxygen molecules into atoms by electrons. A more detailed mechanism for the silent discharge is given.

The Further Concentration of S34

David W. Stewart and Karl Cohen

J. Chem. Phys. 8, 904 (1940); http://dx.doi.org/10.1063/1.1750604 (4 pages) | Cited 9 times

Online Publication Date: 29 December 2004

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A further application has been made of the chemical exchange reaction between sulfur dioxide gas and a solution of sodium bisulfite to the problem of securing higher concentrations of sulfur of atomic weight 34. The exchange reaction was carried out in a series of counter‐current fractionation columns which previously had been used for the separation of the nitrogen and carbon isotopes. Using three fractionation units in cascade arrangement, we have secured sulfur containing 25 percent S34 at a rate of 3.2 grams per day, and have produced sufficient material for a large number of tracer experiments.

The Absorption Spectra of Europium Ion in Some Hydrated Salts

F. H. Spedding, C. C. Moss, and R. C. Waller

J. Chem. Phys. 8, 908 (1940); http://dx.doi.org/10.1063/1.1750605 (11 pages) | Cited 6 times

Online Publication Date: 29 December 2004

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The absorption spectra of crystalline EuCl3⋅6H2O, EuBr3⋅6H2O, and Eu2(SO4)3⋅8H2O were photographed at various temperatures in the visible and ultraviolet region of the spectra. The salts were found to have low‐lying excited levels at about 300 cm‐1, 390 cm‐1, 938 cm‐1, 970 cm‐1 and, perhaps, 430 cm‐1, which arose from excited electronic, crystal and vibrational frequencies. These levels are discussed in relation to existing theories of specific heat, magnetic susceptibility, etc., of europium.

The Normal Vibrations of Molecules of the Tetramethylmethane Type

Samuel Silver

J. Chem. Phys. 8, 919 (1940); http://dx.doi.org/10.1063/1.1750606 (15 pages) | Cited 12 times

Online Publication Date: 29 December 2004

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The normal modes of a tetrahedral A(CH3)4 molecule have been investigated. For fixed orientations of the methyl groups, there are two configurations in which the molecule as a whole possesses the symmetry group Td. The group theory analysis has been applied to one of these configurations, referred to as the eclipsed form, and on the basis of Redlich's theorem a set of symmetry coordinates has been derived for each set of equivalent points. Every symmetry coordinate is associated with an irreducible representation of the group, and, as a consequence, the secular determinant is factored to the maximum extent possible on symmetry considerations alone. Using a simple valence potential, the secular equations for the totally symmetric and doubly degenerate modes have been developed. Calculations have been made for tetramethylmethane, C(CH3)4, tetramethylsilane, Si(CH3)4, and the tetramethylammonium ion, N+(CH3)4, assuming in every case that the force constants associated with the methyl groups are the same as in ethane. The results are in reasonable agreement with frequencies observed in the Raman spectra and a tentative assignment of the latter is suggested.

The Entropy of Dilution of Strong Electrolytes in Aqueous Solutions

H. S. Frank and A. L. Robinson

J. Chem. Phys. 8, 933 (1940); http://dx.doi.org/10.1063/1.1750607 (6 pages) | Cited 32 times

Online Publication Date: 29 December 2004

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The relative partial molal entropy of water, S1☒S10, in aqueous electrolyte solutions is calculated from existing data. An attempt is made to correlate these values with changes in the structure of water in the solutions. It is found that cations of small radii and ions capable of forming hydrogen bonds with the water, such as H3O+, OH— and NH+4, help to stabilize the water structure, while large ions and ions of nonspherical and nontetrahedral shapes have an effect in the opposite direction. In dilute solutions the entropy of dilution depends largely on the ionic strength. In all cases deviations from the Debye‐Hückel limiting law are positive.

Diamagnetic Anisotropy and Electronic Structure of Aromatic Molecules

Harvey Brooks

J. Chem. Phys. 8, 939 (1940); http://dx.doi.org/10.1063/1.1750608 (11 pages) | Cited 9 times

Online Publication Date: 29 December 2004

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Previous theories of the diamagnetic anisotropy of aromatic molecules, based on the method of molecular orbitals, neglect the correlation effects between electrons. In the present theory the anisotropy is treated from the standpoint of the Heitler‐London‐Pauling‐Slater approximation by the inclusion of ionic terms in the secular equation. By means of an approximate treatment it is shown that correlation effects tend to reduce the diamagnetic susceptibility, the effect being relatively greater in complex molecules than in benzene. The contribution of higher order permutation integrals is also discussed and found to be negligible. The correct approximation lies intermediate between the pure H‐L‐S‐P and pure molecular orbital approximations, but in order to explain the high value of the anisotropy, one is forced to assume that the true situation lies much closer to the molecular orbital viewpoint. The variation of the anisotropy of benzene through all intermediate stages of approximation is discussed by means of a more exact model. All calculations were carried out by treating the permutational degeneracy by means of the Dirac vector model.

Separation by Thermal Diffusion of Mixtures of Gases Having the Same Molecular Weight

F. T. Wall and C. E. Holley

J. Chem. Phys. 8, 949 (1940); http://dx.doi.org/10.1063/1.1750609 (5 pages) | Cited 6 times

Online Publication Date: 29 December 2004

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Separations by means of thermal diffusion of mixtures of gases having the same molecular weight have been investigated experimentally and theoretically. Six pairs of gases were considered, namely: CO2☒C3H8, CO2☒N2O, N2O☒C3H8, CO☒C2H4, CO☒N2, and N2☒C2H4. The experiments were carried out in a thermal diffusion column 274 cm long. Assuming the molecules to behave as rigid elastic spheres, theoretical calculations were made for the various combinations and the results compared with the experiments. Except for the pair CO2☒N2O, the theory and experiment agree as to order of magnitude and direction of separation.

The Thermodynamics of Films: Energy and Entropy of Extension and Spreading of Insoluble Monolayers

William D. Harkins, T. Fraser Young, and Edward Boyd

J. Chem. Phys. 8, 954 (1940); http://dx.doi.org/10.1063/1.1750610 (12 pages) | Cited 27 times

Online Publication Date: 29 December 2004

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The thermodynamic relations of insoluble monolayers on a mobile subphase are given, and equations are presented for their (a) increase of entropy, (b) heat absorbed, (c) increase of heat content, and (d) increase of internal energy, during expansion. Two different methods of expansion are considered: in spreading the decrease of area of the subphase is equal to the increase of area of the monolayer; in extension the monolayer expands but the area of the clean surface of the subphase remains constant. The two‐dimensional phases are classified as: I. gas; II. liquid (L1) expanded; III. intermediate or transition; IV. liquid (L2) condensed; and V. solid. The extreme limits of molecular area for the intermediate liquid phase are for pentadecylic acid about 22 and 44A2, while those for the liquid phases IV, III, and II, are from about 20.5 to 52A2 which indicates that, beginning with a two‐dimensional liquid in its most condensed condition, the mean molecular distances may be increased by as much as 60 percent without a destruction of the liquid state. This is very different from what is found in three dimensions. The heat absorbed in the melting of the two‐dimensional solid is zero, so this is phase change of the second order. The quantity, hs = (∂Hs/∂σ)p,T, which is the increase in heat content when the monolayer spreads over unit area, has a value of several hundred ergs cm—2 for a solid film. The increase of heat content for the other two‐dimensional phases may be illustrated by the approximate values for pentadecylic acid: it is zero for (L2), or the liquid condensed phase; rises in the intermediate phase very gradually to a nearly constant magnitude of 300 ergs cm—2 as the area is increased and decreases to about 50 erg cm—2 in the liquid expanded phase (L1). For any two‐dimensional phase spread on water or on mercury the value of h for extension is greater than that for spreading by he the total surface energy of the three‐dimensional liquid, which is about 116 erg cm—2 for water, and 540 for mercury. The increase of heat content ΔHm during the spreading of a mole of pentadecylic acid has been calculated for the case in which the film spreads from the lowest to the highest area at which the phase exists. For the solid phase this energy is of the order of about a fifth of a kcal. mole—1 at 18°C, while ΔHm for the intermediate phase is 8.3 kcal. mole—1, and for the liquid expanded (L2) phase is very small. At 25°C the value for the intermediate phase has fallen to 4.6, and that for the liquid expanded phase (L2) has increased to 1.0 kcal. mole—1.

Effect of Gravitational Field on the Thermal Diffusion Separation Method

Milton Farber and W. F. Libby

J. Chem. Phys. 8, 965 (1940); http://dx.doi.org/10.1063/1.1750611 (5 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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A test of the effect of gravitational field on the operation of the Clusius‐Dickel thermal diffusion method for gas separation has been made by use of a hollow disk with one hot surface, the whole disk spinning at various speeds. Linear increases in both the equilibrium separations and the rates of separation with increasing centrifugal force were obtained for speeds below a certain maximum value. Above this both the rate and equilibrium separations fell rapidly. He☒CO2 mixtures were used. The results indicate that the standard column would be improved if it were placed in a larger field up to ten times that caused by gravity. Theories for the action of the thermal diffusion column should show this. The apparatus cannot compete with the standard column type for isotopic separations but may have some application to industrial separation problems.

The Low Temperature Gaseous Heat Capacities of Certain C3 Hydrocarbons

G. B. Kistiakowsky, J. R. Lacher, and W. W. Ransom

J. Chem. Phys. 8, 970 (1940); http://dx.doi.org/10.1063/1.1750612 (8 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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The low pressure thermal conductivities of allene, propylene, propane, methyl acetylene and cyclopropane have been measured over the temperature range 150 to 340°K. The heat capacities derived from these measurements are compared with those from other sources. Data are presented in support of the bracketing method for deriving heat capacities from heat conductances. Heats of certain hydrogenation reactions, when calculated to 0°K and to the nonvibrating state, are found to exhibit the same regularities as the experimental values determined at 335°K.

Statistical Theory of Duplex Films

Lawrence S. K. Feng and William Band

J. Chem. Phys. 8, 977 (1940); http://dx.doi.org/10.1063/1.1750613 (4 pages)

Online Publication Date: 29 December 2004

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The dissociation treatment of condensing systems is applied to duplex films. Complete agreement with the data on the saturated state of the films of myristic acid published by Adam and by Harkins is obtained on the following assumptions: (i) the momentum of each entire molecule contributes to the monolayer gas pressure; (ii) the interaction potential between the ``liquid ends'' of the molecules is equivalent to an ``intrinsic pressure'' which has the effect of increasing the surface tension at the interface between parent liquid and monolayer; (iii) this intrinsic pressure is derivable from a Lennard‐Jones type of interaction potential depending on mean molecular area: W=W0+α/A4.5—β/A3; (iv) the tails of the molecules can form clusters, thus forming micelles in the duplex film, in which there are six bonds per molecule, each with interaction energy ϵ=—8.8×10—14 erg per molecule. The field constants α, β seem to depend slightly on the nature of the parent liquid, but the energy ϵ is independent of this. The duplex film therefore appears to have its liquid layer in contact with the parent liquid, the free tails forming the gas layer. More data on different parent liquids are needed before a definite decision on this point can be made.

The Gaseous Heat Capacity and Restricted Internal Rotation of Diborane

Fred Stitt

J. Chem. Phys. 8, 981 (1940); http://dx.doi.org/10.1063/1.1750614 (6 pages) | Cited 12 times

Online Publication Date: 29 December 2004

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The heat capacity of gaseous diborane has been measured from 95° to 324°K with the low pressure thermal conductivity apparatus described earlier. The bracketing method was applied over most of this temperature range, with acetylene and ethylene as comparison gases. At 95°K, ethylene and ethane were used as comparison gases and the accommodation coefficient ratios were assumed to be unity. The heat capacity at low temperatures indicates that internal rotation in the diborane molecule is restricted by a potential barrier whose height is probably between 4000 and 6000 cal./mole if the barrier is assumed to be a sinusoidal function of the internal rotational angle.

A Theoretical and Experimental Analysis of the Capillary Rise Method for Measuring the Surface Tension of Solutions of Electrolytes

Grinnell Jones and Laurence D. Frizzell

J. Chem. Phys. 8, 986 (1940); http://dx.doi.org/10.1063/1.1750615 (12 pages) | Cited 9 times

Online Publication Date: 29 December 2004

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Jones and Ray made measurements of the capillary rise of solutions of electrolytes which they interpreted as showing that there is a minimum in the surface tension‐concentration curve at low concentration (about 0.001N). Langmuir has suggested that the liquid film above the meniscus may be several hundred angstroms thick and may be sufficiently different for water and for solutions of electrolytes to account for the observed capillary rises without drawing the conclusion that there is a minimum in the surface tension. Langmuir's theory is analyzed in detail and one of its premises is shown to be inconsistent with experimental evidence of several kinds which indicates that a solution‐air interface is electrically charged. Langmuir's theory gives the thickness of the wetting film as an explicit function of the concentration and temperature of the solution; and of the capillary rise (which depends on the radius of the tube and on the surface tension of the liquid); and of the zeta‐potential. But unfortunately zeta‐potentials are not known with sufficient precision to permit reliable calculations of the thickness of the wetting film. Some of the consequences of the theory are tested experimentally.
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Note on the Chain Photolysis of Acetaldehyde in Intermittent Light

W. L. Haden, E. P. H. Meibohm, and O. K. Rice

J. Chem. Phys. 8, 998 (1940); http://dx.doi.org/10.1063/1.1750616 (1 page) | Cited 3 times

Online Publication Date: 29 December 2004

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Erratum: High Velocity Atomic Beams

I. Amdur and H. Pearlman

J. Chem. Phys. 8, 998 (1940); http://dx.doi.org/10.1063/1.1750617 (1 page)

Online Publication Date: 29 December 2004

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