Herrick L. Johnston

The Absorption Spectra of Methane, Carbon Dioxide, Water Vapor, and Ethylene in the Vacuum Ultraviolet

Quantitative absorption measurements were made of methane, carbon dioxide, water vapor, and ethylene at 30°C in a Cario and Schmidt‐Ott vacuum fluorite spectrograph from 1400 to 2000A. Values of the atmospheric absorption coefficient, α, in the equation, I=I0 exp(—αx), ranging from two for carbon dioxide to 800 for ethylene were found. Resonance wave‐lengths and oscillator strengths were calculated from absorption curves and found to be consistent with refractive index data.

High Temperature Structure and Thermal Expansion of Some Metals as Determined by X‐Ray Diffraction Data. I. Platinum, Tantalum, Niobium, and Molybdenum

The crystal structure and thermal expansion of platinum, tantalum, niobium, and molybdenum have been determined between 1100° and 2500°K. These metals were found to undergo a uniform thermal expansion over the temperature range of this investigation and to undergo no structural change. The permanent elongation of tantalum wires, produced by annealing at temperatures between 2473° and 2773°K, appears to be caused by reorientation of crystal grains in the specimen and to preferred direction of crystal growth during annealing, rather than to a change in crystal structure.Quadratic equations have been developed for the thermal expansion of platinum, tantalum, niobium, and molybdenum. These equations are represented, respectively, by Δa0/a0=7.543×10−6(T−291)+2.362×10−9(T−291)2,Δa0/a0=6.080×10−6(T−291)+7.50×10−10(T−291)2,Δa0/a0=7.591×10−6(T−291)+6.96×10−10(T−291)2, and Δa0/a0=0.987×10−3+2.40×10−6(T−273)+2.20×10−9(T−273)2.Values of the expansion coefficient α were computed for each of the metals by differentiati...

The Thermal Conductivites of Eight Common Gases between 80° and 380°K

Thermal conductivities of O2, N2, CO, NO, H2, He, N2O, CO2, and CH4 have been measured between 80°K and 380°K, with the potential lead type of hot wire cell developed by Taylor and Johnston. Results—which have a precision generally better than 0.1 of one percent and are believed to be accurate to ±0.5 of one percent—are tabulated for the eight gases. Comparisons with the results of other investigators are also shown in tabular form.

The Infrared and Raman Spectra of Condensed Nitric Oxide

The infrared and Raman spectra of liquid and solid nitric oxide have been studied in an attempt to prove the existence of the (NO)2 molecule. The liquid has four strong Raman lines at 1861, 262, 196, and 167 cm−1; two weaker Raman lines at 1760 and 487 cm−1; and two strong infrared bands at 1863 and 1770 cm−1. Several weaker infrared bands can be satisfactorily assigned as combinations by using the observed strong infrared and Raman frequencies. The spectra were found to be due exclusively to a dimer which probably exists as a bent ONNO molecule.

The Intermolecular Force Constants of Fluorine

The intermolecular force constants of gaseous fluorine have been determined from measurements of the second virial coefficients in the region 80–300°K. On the assumption that gas imperfection results only from binary collisions of spherical nonpolar molecules whose potential is of the form given by Eq. (1), the force constants obtained were r0=3.61±0.04A and e0/k=121±3°K. These force constants yield viscosities in good agreement with the experimental data of Kanda if the high temperature point is discarded.

Thermal Expansion of Zirconium between 298°K and 1600°K

The average coefficients of thermal expansion of hexagonal zirconium between 298°K and 1143°K are 5.5×10−6 deg−1 along the a axis, 10.8×10−6 deg−1 along the c axis, and 7.2×10−6 deg−1 for a randomly oriented polycrystalline sample. The average value of the linear coefficient of expansion of cubic zirconium between 1143°K and 1600°K is 9.7×10−6 deg−1. At the transition there is a decrease in volume of 0.66 percent.

A Variable Thickness Low Temperature Infra-Red CeH*,†

An infra-red absorption cell has been designed and constructed for use at low temperatures. This cell incorporates flat silver chloride windows and possesses a mechanism for varying the sample thickness with the cell in place. The present cell is satisfactory for use down to about liquid hydrogen temperatures but, with some minor changes, can be redesigned for use at lower temperatures.

Accommodation Coefficients for Heat Conduction Between Gas and Bright Platinum, for Nine Gases Between 80°K (or Their Boiling Points) and 380°K

Accommodation coefficients toward bright platinum for air, oxygen, nitric oxide, carbon monoxide, carbon dioxide, nitrous oxide, methane, hydrogen, and helium are computed from the (1/Ka) versus (1/P) slopes of the thermal conductivity measurements of Taylor and Johnston and of Johnston and Grilly. The results—which cover the temperature range 80°K to 380°K—are tabulated for the several gases, and are collected in a graph where comparison with results obtained by other investigators are also included. Our results with hydrogen rise toward a coefficient of unity with lowering temperature, in confirmation of measurements by others, but those for other gases drop steeply at temperatures between room temperature and that of liquid air. Our data are in generally good agreement with the recent accurate work of Amdur, Jones, and Pearlman, at room temperature. The accommodation coefficients which are derived from the reciprocal K versus reciprocal P plots differ slightly from Knudsen accommodation coefficients, a...

A Note on the Vibrational Frequencies and the Entropy of Decaborane

The infrared spectra of solid decaborane and of decaborane in a solution of carbon disulfide as well as the Raman spectrum of the solution have been recorded. A rough selection of fundamental frequencies is made; this, together with the molecular parameters from x‐ray data, is used for calculating S298.160 of the gas, for which a value of 83.85 eu is obtained. This figure compares with that derived from thermodynamic measurements, namely, 87.36 eu.

Design and Operation of Liquid Nitrogen‐Cooled Solenoid Magnets

This paper describes the design and construction of compact iron‐free solenoid magnets cooled by immersion in liquid nitrogen. Construction details and performance data are given for two such magnets, which produce a magnetic field of 4000 gauss with a power expenditure of 2.7 to 3.3 kw. Heat transfer coefficients between copper wire and boiling liquid nitrogen have been measured for temperature differences between the wire and the liquid of 2 to 11°K.