John G. Berberian

Nonlinear AC and DC Polarization of Platinum Electrodes

The ac and dc induced nonlinearities of platinum electrodes in KCI solution were investigated and the effects of the rectification were significant only in the presence of externally applied dc. The experimental dependence of the overpotential as a function of applied ac and dc is presented and in qualitative agreement with the Tafel law.

The steady‐state shear viscosities of some chloropentanes

The steady‐state shear viscosities of 3‐methylpentane, 3‐bromomethylpentane, 3‐bromopentane, and 3‐bromo‐3‐methylpentane are presented as a function of temperature. The temperature range of the measurements is from 138 down to 76 K; the range of viscosities measured is from 3.07×101 up to 1.80×1011 Pa s.

Time domain reflectometry: Bilinear corrections and extending the range of analysis beyond the quarter and half wavelength conditions

Abstract The analysis for the determination of bilinear coefficients for time domain reflection measurements are presented here. The calculation of the coefficients is based on a short circuit and a standard liquid as calibration standards. The range of frequencies used in this anaylsis goes up to the frequency equivalent of the half wavelength condition for a coaxial transmission line terminated with a dielectric e•. The Newton-Raphson algorithm for the calculation of e• from e•tan(ωd/c)√e•)/(ωd/c)√e•) is also presented.

Dielectric relaxation of 3-bromopentane in mixtures with 3-methylpentane

Abstract Dielectric measurements of mixtures of 75, 50 and 25 mol% 3-bromopentane (3BP) in 3-methylpentane are presented in the temperature range 85–112 K. The data obtained from ac and transient measurements are in the frequency range from 100 kHz to below 1 μHz (transient data are transformed to the frequency domain). Previous dielectric studies and a recent measurement on pure 3BP fit the Cole-Davidson (CD) skewed arc within the limits of the experiment. However, measurements reported here on the mixtures yield a better fit to the Kohlrausch-Williams-Watts (KWW) function than to the CD skewed arc. A log plot of best-fit KWW relaxation times (KWWτ) against reciprocal temperature appears to be linear for the temperature range of the measurements (all mole fractions) unlike the Vogel-Tammann-Fulcher behavior of pure 3BP. Due to the limited temperature range, only a comparison of isothermal relaxation times between adjacent concentrations can be made directly: at 111 K, the KWWτ for pure 3BP is 2.5 s and that for 75% 3BP is 0.0018 s; at 100 K, the KWWτ for 75% 3BP is 104 s and that for 50% is 0.0687 s; at 90.9 K, the KWWτ for 50% 3BP is 402 s and that for 25% is 0.444 s.

The dipole moments of some chloro‐ and bromopentanes

The dipole moments of 3‐chloropentane, 3‐chloromethylpentane, 3‐chloro‐e‐methlypentane, 3‐bromopentane, 3‐bromomethylpentane, and 3‐bromo‐3‐methylpentane are reported in this note; the total polarizations of these comopounds aer also presented. The measurements of the total polarization on these comppounds were made as a function of solute concentration in benzene at 25 °C and extrapolated to zero solute concentration. (AIP)

Cell design for low‐temperature time‐domain reflectance measurements

The design and construction of a dielectric cell, used in time‐domain reflectance measurements at low temperature and high frequencies, are presented. Criteria are developed for cell construction, based on a transmission line model of bilinear form, and are applied to the physical construction of the cell. Bilinear parameters are derived for the cell model and compared with parameters calculated from short circuit measurements of two cells differing in design.

The Dielectric Relaxation of 3-Bromomethylpentane

The dielectric premittivity of supercooled 3-bromomethylpentane in the temperature range of 145 K down to 114 K is reported here. Data were obtained by steady-state ac bridge measurements in the frequency range from 105 Hz down to 20 mHz and by transient measurements for relaxation times from 2 up to 2500s. With exception of the high-frequency data, the data are described by the skewed are relaxation function, and the relaxation parameter ß is seen to approach 0.50 at the lowest temperature. The temperature dependence of the relaxation times can be represented by the empirical expression of Vogel with T¿ = 87.6 K.

A method for measuring small rotational velocities for a couette‐type viscometer

A parallel plate capacitor assembly is used to measure the angular rotation in viscosity measurements using a Couette‐type viscometer. This measurement coupled with a time base permits extremely small angle velocities to be measured thus permitting large viscosities (ca. 1011 Pa s) to be determined. Sample data on supercooled isoamyl bromide at low temperatures obtained by this method are presented.

Time study of the dielectric permittivity of supercooled 3-bromopentane during crystallization

Abstract The isothermal dielectric permittivity of pure supercooled 3-bromopentane has been measured as a function of time at several fixed temperatures, ranging from 110 to 120 K. Transient measurements are used to expedite the measuring time and are transformed to give an equivalent frequency range from several kilohertz to a few microhertz. A set of isothermal static permittivities measured over a period of time is presented, and the changes in the static permittivity with time clearly indicate that crystallization is occurring at a rate which is a function of the temperature difference from the melting point. The permittivity of pure 3-bromopentane has been fitted to the Cole-Davidson function. The values of the Cole-Davidson parameters determined as a function of time for each of the temperature sets of data are presented.

Static viscosity of supercooled 3-bromopentane in mixtures with 3-methylpentane

Static viscosity measurements of two mixtures of 3-bromopentane in 3-methylpentane are presented in the temperature range from 94 to 112 K and over a range of viscosities from 3 × 107 to 280 Pa s. The data are fitted to the Vogel-Fulcher-Tamman equation. Estimates of the glass transition temperatures for these mixtures based on the reference viscosity of 1 × 1012 Pa s are 90.1 and 98.8 K for 0.500 mole fraction and 0.750 mole fraction of 3-bromopentane in 3-methylpentane, respectively. Additionally, viscosity measurements on pure 3-methylpentane, previously reported, have been extended to higher temperatures. These viscosity values and those measured in this laboratory on 3-bromopentane, along with estimates of their glass transition temperatures, are also presented for comparison purposes.