John L. Margrave

Infra-red spectra of inorganic solids—II oxides, nitrides, carbides, and borides

Abstract A series of oxide, nitride, carbide, and boride samples were scanned in the rock-salt region of the infra-red. The KBr disk technique was employed for the examination. The spectra show certain characteristic bands for each of the sets of compounds studied. Changes in band position for the major bands were noted with changes in mass for a number of the samples.

Mass‐Spectrometric Studies at High Temperatures. II. The Dissociation Energies of the Monofluorides and Difluorides of Silicon and Germanium

Calcium fluoride has been used to fluorinate silicon and germanium in a heated Knudsen cell in a mass spectrometer. Second‐ and third‐law calculations using effusion data for the gaseous monofluoride and difluoride species produced at temperatures up to 1575°K are in good agreement and lead to the following atomization energies: D°298[SiF(g)]=5.61±0.2 eV, ΔH°a,298[SiF2(g)]=12.33±0.2 eV, D°298[GeF(g)]=5.04±0.2 eV, and ΔH°a,298[GeF2(g)]=10.0±0.8 eV.

Absorption Spectrum of Fluorine in the Vacuum Ultraviolet

The absorption spectrum of F2 has been observed in the vacuum ultraviolet region. A special windowless absorption apparatus and a Lyman discharge light source were used in combination with a one‐meter normal incidence spectrograph.A Rydberg series establishes the ionization potential of F2 as 15.7 ev. From a progression of bands at 874 A, one can deduce the dissociation energy of fluorine as 37.5±2 kcal/mole. The binding energy of F2+ is 3.3 ev. The low value of the ionization potential is consistent with the observed low value of the dissociation energy.

Infra-red spectra of inorganic solids—I: Peroxides, peroxide hydrates, and superoxides

Abstract A number of peroxide, peroxide hydrate, and superoxide samples were scanned in the rock salt region of the infra-red. For this scan, a special modification of the KBr disc technique was developed. The spectra show only carbonate and water to be the major impurities except for the hydrate samples where water is already combined. An indication of any structural detail for these hydrate samples was not observed.

Mass Spectrometric Studies at High Temperatures. III. Dissociation Energies of the Alkaline Earth Monofluorides

By heating the difluorides of magnesium, strontium, and barium under reducing conditions, one obtains significant amounts of the respective monofluorides. Mass spectrometric studies of equilibria involving these monofluorides have yielded the dissociation energies (D°298) 4.62±0.1 eV, 5.43±0.1 eV, and 5.83±0.1 eV for gaseous MgF, SrF, and BaF, respectively. These results support an ionic model for these molecules and are considerably higher than those previously accepted.

Mass Spectrometric Studies at High Temperatures. II. The Sublimation Pressures of Magnesium, Strontium, and Barium Fluorides

A mass spectrometer has been employed to measure the sublimation pressures and heats of sublimation for MgF2 over the range 1241° to 1492°K; for SrF2 over the range 1207° to 1563°K; and for BaF2 from 1232° to 1505°K. For MgF2 the results are represented by logPatm=−[(88.3±0.9)/45.76]104T−1+8.53±0.2; for SrF2 by logPatm=−[(99.3±0.7)/45.76]104T−1+8.716±0.01; and for BaF2 the equation is logPatm=−[(85.1±0.9)/45.76]104T−1+7.659±0.01. The errors quoted are the standard deviations from the least‐squares fitted lines. The heat of sublimation of MgF2 at 1366°K is 88.3±2.5 kcal mole—1 while the heats of sublimation at 298°K are 103.7±2.5 kcal mole—1 for SrF2 and 92.3±2.0 kcal mole—1 for BaF2.

ELECTRON AFFINITY OF FLUORINE

Various theoretical and semi‐empirical methods for determining electron affinities of atoms have been applied to fluorine. All results indicate a low value of the electron affinity consistent with recent experimental data, and with the value implied by the recently determined dissociation energy of the fluorine molecule. An extrapolation of the type suggested by Hellmann and Mamotenko appears to give the most reliable value and indicates EF=83.2±0.3 kcal/mole.

Vapour equilibria in the B2O3H2O system at elevated temperatures

The equilibrium pressures of H/sub 3/BO/sub 3(/>i,HBO/sub 2(/>i,and (HBO/ sub 23(/>i were determined by a transpiration method in the temperature region 1000 to 1273 deg K. From these data the calculated heats of formation are DELTA H/sub fo i/sub K/ STAHBO/sub 2(/>i!=134.9 plus or minus 1 kcal/mole and DELTA H/sub fo i/sub K/ STA(HBO/sub 2/)/sub 3(/>i!=-537.5 plus or minus 3 kcal/mole.

Evidence for two new crystalline forms of sodium peroxide

Abstract A diffractometer equipped with a special furnace was used to record the powder diffraction pattern of Na2O2 over the range 25–550°C. A new phase, Na2O2-II, is stable at high temperatures. The transition temperature was found from diffractometer and separate thermal analysis measurements to be 512 ± 1°C. The thermal expansion coefficient of Na2O2-I, from diffractometer data, was found to be essentially isotropic and linear within the limit of error, and equal to (2·84 ± 0·4) × 10−5 °C−1 (15–460°C). Samples prepared by pouring molten sodium peroxide into liquid air gave a powder diffraction pattern at room temperature which is tentatively identified as that of a third polymorph, Na2O2-Q.

The X-ray powder diffraction pattern and density of solid perchloryl fluoride

Abstract The X-ray powder diffraction pattern and the density of solid ClO 3 F have been determined at liquid air temperatures. From the powder data it appears that crystalline ClO 3 F is tetragonal.