Volume 1, Issue 1, 01 January 1933
Index of content:
1(1933); http://dx.doi.org/10.1063/1.1749216View Description Hide Description
An adsorption field is defined as a homogeneous part of a solid or liquid surface on which adsorption can occur. In presence of adsorbable components each field contains one or more surface phases.Adsorption experiments have demonstrated that in many cases all the intrinsic properties of an isolated surface phase are variables characterized by C+1 degrees of freedom (F) where C is the number of components. If this surface phase postulate (S.P.P.) applies to each surface phase in a system, then, for a system in a state of complete equilibrium, F has the value F 0 = C+S —Pv —Ps +2 where S, Pv and Ps are the numbers of fields, volume phases and surface phases, respectively. By considering the possible mechanisms, such as interphase mobility and vapor interchange by which equilibrium may be attained, this phase rule is extended to states of partial equilibrium, for example, cases where the surface phases and the volume phases are at different temperatures. The effects of electric fields are considered. Non‐equilibrium states, which may be divided into steady states and transient states are characterized by values of F greater than F 0. Experiments on transients by which F can be determined may thus serve to determine S when it is otherwise unknown. If the geometrical arrangement of the surface phases is known, such experiments serve to determine the surfacediffusion coefficient D, or the phase boundary resistance to diffusion. The applicability of the S.P.P. depends on a certain degree of intraphase mobility of the adatoms.
1(1933); http://dx.doi.org/10.1063/1.1749213View Description Hide Description
1(1933); http://dx.doi.org/10.1063/1.1749215View Description Hide Description
A series of iron oxides with compositions between 76.08 and 76.72 percent Fe, all of them lying within the single phase solid solution area known as Wüstite has been prepared and the lattice constants and densities of the individual members determined. The NaCl structure found by earlier investigators and considered by them to be the structure of FeO has been found throughout this series. Contrary to the earlier results the size of the unit cell decreases as the iron content decreases. The solid solution is of a complex type; an oxygen ion replaces an FeO group with an accompanying increase in valence of 2 Fe++ to 2 Fe+++. The results are discussed from the chemical and structural points of view.
A Spectroscopic Study of the Decomposition and Synthesis of Organic Compounds by Electrical Discharges: Electrodeless and Glow Discharges1(1933); http://dx.doi.org/10.1063/1.1749217View Description Hide Description
In the chemical reactions which occur in electrical discharges through organic vapors and in the maintenance of the discharge, the simple ionization of the molecules, and the resultant formation of clusters, is found to be less important, and the breaking down into molecular, atomic and ionic fragments, more important than has heretofore been supposed. The fragments revealed by the spectroscope are CH, OH, NH, C2, CN, N2, CO, CO+, CS, S2, H2, C, C+, H, and S, and in addition H2O and NH3 are known to be formed. When the electrodeless discharge is in benzene vapor the pressure is rapidly lowered until the discharge is extinguished, but this effect is not found with the glow discharge. As compared with the electrodeless discharge, the spectrum from the glow discharge differs in the following respects: the C2 bands are much less intense and only the fourth group of Swan bands appears appreciably. The line spectrum of C is less intense, and the prominent λ4267 line of C+ disappears. The CH bands are very clear and that at λ3900 is closer in intensity to that at λ4300 than in the electrodeless discharge. The Balmer series of hydrogen is slightly more intense, and the many‐line spectrum of H2, not present with the electrodeless discharge, is prominent. In general the greatest intensity of the spectrum is given by the cathodeglow and the edge of the negative glow near the cathode. The Crookes dark space is a region of very low intensity. The Balmer lines are of nearly uniform intensity throughout except for a specially high intensity just at the cathode. The many line spectrum of hydrogen differs from the others in that it is scarcely visible in the cathodeglow. With phenol many bands due to CO and CO+ dominate the spectrum of the glow discharge, though they are not found in the electrodeless discharge. In the electrodeless discharge the rate and nature of the reaction and the spectrum emitted are affected by the hydrogen to carbon ratio in such a way that the rate of reaction decreases as this ratio increases, and the fraction of gaseous products and the intensity of the spectra emitted by molecules which contain hydrogen increase with this ratio. Thiophene is decomposed into sulfur atoms (S), and molecules (S2), and carbon monosulfide molecules (CS) in addition to molecules of carbon (C2) and of monohydrocarbon (CH), atoms of hydrogen (H) and of carbon (C), and ions of carbon (C+) as had been shown before for the hydrocarbons. In the glow discharge both saturated and unsaturated hydrocarbons are decomposed at about the same rate to form the molecules and atoms listed above. The decomposition products from the glow unite to form brown or black solids somewhat similar to those formed in the electrodeless discharge. From the way in which the product is deposited and the intensity of the spectrum, the reaction is seen to be most rapid at the cathodeward edge of the negative glow.
1(1933); http://dx.doi.org/10.1063/1.1749218View Description Hide Description
The infrared absorption spectra of ethyl chloride, ethyl bromide and ethyl iodide have been determined with a prismspectrometer between 1.5μ and 15μ. Eight experimentally observed fundamental frequencies have been selected which, together with their first harmonics and simple combinations, are shown to account for the entire spectrum. A type of vibration between atom pairs believed to represent the important feature of the motion of the atoms is suggested for each of these fundamentals. The shifts in the absorption maxima produced by the substitution of the different halogens together with absorption and Raman data of related compounds are used in selecting these types of vibration. The bearing of these hypotheses on problems in chemical kinetics is discussed.
1(1933); http://dx.doi.org/10.1063/1.1749219View Description Hide Description
With the use of wave functions constructed from hydrogen‐like single‐electron functions with an effective nuclear charge Z, the application of the variation method of treating the wave equation for the normal state of He2 +, involving a three‐electron bond, leads to the values Z = 1.833, r 0 = 1.085A, De = 2.47 v.e., and ω0 = approximately 1950 cm—1. The experimentally determined values (from the He2 spectrum) are r 0 = 1.090A, De = 2.5 v.e., and ω½ = 1628 cm—1. A similar discussion of He2 ++, with a covalent‐plus‐ionic wave function, shows that the energy curve has a minimum at r 0 = 0.75A, ω0 = approximately 3200 cm—1, with a maximum 1.4 v.e. higher at about 1.1A. This configuration could act as the core for excited states of He2 + and doubly‐excited states of He2, some of which would be capable of existence with either one of two moments of inertia, one corresponding to r 0 = 0.75A and the other to about the same values of r 0 as for the analogous states in excited H2 + or doubly‐excited H2.
1(1933); http://dx.doi.org/10.1063/1.1749221View Description Hide Description
The melting points of various isomeric organic compounds indicate that molecular symmetry has an important effect on physical properties. With R. H. Fowler's statistical treatment of the crystal state, the symmetry number has been calculated for benzene and cyclohexene. The data employed are the vapor pressure, the heat capacity of the crystal, the heat capacity of the vapor as calculated from Raman spectra, the heat of sublimation and the moments of inertia. According to this calculation the symmetry number for benzene has the value 6±0.5 indicating that the molecule is not plane. The symmetry number for cyclohexene is 2±0.2 as is to be expected.
1(1933); http://dx.doi.org/10.1063/1.1749222View Description Hide Description
First order perturbation theory has been employed to compute the binding energies of various geometrical configurations of three to eight atoms of sodium. It has been assumed that in the metal lattice the binding is essentially homopolar. It has been shown that the growth of a unit cell probably proceeds via the diatomic molecule to a square, a fifth atom adding along a cube edge, a sixth at the body center and the cell completed by location of atoms at the remaining cube corners. The unit cell is still a very unstable unit, a result in agreement with high vapor pressures and solubility of finely divided particles, and with the concept of active centers on reactionsurfaces. The fifth order secular equation employed to determine the energies of configurations of five and six atoms has been made more amenable to use in calculations. A fourteenth order secular equation, with similar characteristics, has been employed for the cases of seven and eight atoms. Approximate calculations with copper atoms instead of sodium give similar results but indicate that higher activation energies of nuclei formation may obtain in this case. The percentage of the total binding assigned to interchange is shown to be an important factor. The calculations indicate that the net effect of interchange forces in homopolar crystals is to increase the potential energy. The crystal structure is stable only because of the coulombic and van der Waals' forces. When applied to hydrogen (90 percent interchange) it is shown that a metallic lattice is utterly unstable.
1(1933); http://dx.doi.org/10.1063/1.1749223View Description Hide Description
The thermal decompositions of ethyl mercaptan and ethyl sulphide have been studied by a static method and shown to proceed homogeneously in glass vessels which have become poisoned by products of reaction. The rate curves of both exhibit an induction period shown to be due to a reaction between ethyl and hydrogen sulphides yielding what appears to be a dimercaptan. The subsequent decomposition of this intermediate is unimolecular but complicated by a reverse reaction. The energies of activation of formation and decomposition of the intermediate are each about 40,000 calories, the rate of formation being slightly greater than the rate of decomposition at temperatures around 400°C. The unimolecular rate falls off below 150 mm which would correspond with six squared terms involved in the activation. No foreign gas has been found to maintain the rate. The existence of a complex equilibrium detracts somewhat from the certainty of interpretation of data and mechanism. A critique of similar recent work substantiates the conclusions here drawn though differing from previous interpretations.
1(1933); http://dx.doi.org/10.1063/1.1749224View Description Hide Description
The ignition temperatures of methane‐``air'' mixtures were investigated in a flow system as follows: (1) The spontaneous ignition temperature due to temperature alone was determined. (2) One of the inert gases was passed through a condensed discharge before joining the combustible gas and the change in ignition temperature noted. The individual gases were preheated to 500°C before mixing in the ignition tube which could be heated to any desired higher temperature. Ignition always occurred about 50 cm downstream from the spark chamber. The temperature at which the mixtures ignited was lower when pre‐sparking was employed. The gases subjected to the spark were A, He, N2, O2. The difference between the spontaneous and pre‐sparking ignition temperatures increased in the order named, being about 28°C for A and about 240°C for oxygen under the conditions of this investigation for a final mixture of 8 percent methane in ``air'' (ratio of oxygen to inert gas in final mixture being the same as in air). A post ignition phenomenon is described which is brought about by delaying the flow of the sparked oxygen for some time after cessation of the spark and then resuming the flow. Such delay times of 2½ minutes were observed. The species which cause ignition possess a long life and are rather easily removed by metal screens. It is shown that the results cannot be accounted for by nitric oxide, ozone, active nitrogen or active oxygen. It is concluded that electrically charged species or ions are responsible for the lowered ignition temperatures. A tentative explanation of the results is suggested. It is pointed out that in the ignition of combustible gas mixtures by direct action of a spark, the ions formed in the path of the spark, as well as the thermal energy liberated, play a responsible part in the ignition process.
Low Temperature Specific Heats: III. Molecular Rotation in Crystalline Primary Normal Amyl Ammonium Chloride1(1933); http://dx.doi.org/10.1063/1.1749225View Description Hide Description
The heat capacity of primary normal amyl ammonium chloride was measu red between 20° and 280°K. If the substance is quenched to 90°K a metastable form is obtained which upon heat ing above 165°K slowly changes toward an apparently st able form. Two regions of gradual transition were found. X‐ray powder diffraction photographs taken above and below the transition regions were remarkably similar. The experimental results are interpreted on the basis of rotation of the NH3C5H11 + groups in the crystals.
1(1933); http://dx.doi.org/10.1063/1.1697304View Description Hide Description
In this paper equations are given for the direct treatment of experiments in which not only heat, but also masses, pass the boundary of the container of the system during the experiment. The theoretical development is correlated with the treatment of Gibbs, and certain difficulties, mentioned by others, in the physical interpretation of his equations, are incidentally removed. It was found possible, within a reasonable time, to cause a gas to expand slowly enough from a calorimeter to simulate a reversible expansion, and the special equation developed for the heat of expansion with the aid of the Beattie‐Bridgeman equation of state was verified by the results for the slow expansion of carbon dioxide and ammonia. In the case of carbon dioxide the effect of the deviations from the ideal gas law was to make the heat effect in excess of that calculated for an ideal gas by a sufficient amount so that the excess itself could be calculated within about 7 percent. A series of expansions of carbon dioxide was carried out at varying rates of flow, some as fast as permissible. The results, correlated by means of an empirical relation, serve to show that the results of the slow expansions correspond practically to an infinitely slow expansion. They also indicate that the heat effect for an infinitely rapid expansion is not zero for a real gas, but possibly vanishes with the pressure. In the absence of a perfectly sound method of calculating the heat effect for an infinitely fast expansion, a method is suggested which has at least the merit of agreement with the present experiments.
The bearing of the results on variable‐pressure calorimetry, as practiced in experiments on the heat of adsorption, is briefly discussed.
1(1933); http://dx.doi.org/10.1063/1.1749212View Description Hide Description
Several types of dispersion of sound which may be manifest in a dissociating gas are discussed. Of these only the heat‐capacity dispersion and the dissociation dispersion need be considered under suitable experimental conditions. The expression derived by Einstein for the velocity of sound in a dissociating gas has been modified to include heat‐capacity dispersion. The experimental procedure indicated by this for obtaining significant dissociationrate constants is outlined. Measurements on the velocity of sound in nitrogen tetroxide which have been made with apparatus of special design, are reported. The range of temperature studied is 0°C to 30°C, the range of pressure 132 mm to 670 mm, and the range of frequency 9 kc to 451 kc. The velocity of sound has been thus defined with an estimated error of ±0.1 m·sec.—1. The maximum dispersion which has been observed is about 5 m·sec.—1. From these measurements it appears that the rate constant of the dissociationreaction is 4.8×104±0.5×104 at 25°C and 260 mm. The activation energy obtained for the dissociationreaction is 13.9±0.9 kg·cal. The rate constant appears to diminish slightly as the pressure is reduced. Since an upper limit for the heat capacity of nitrogen tetroxide is fixed by experiment, it is necessary to suppose that the effective molecular diameters for the activation process are at least three times those for ordinary kinetic collisions.