Thermal diffusivity of green river oil shale by the laser-flash technique

The thermal diffusivity of Green River oil shale has been measured by the laser-flash technique. Measurements were carried out in the temperature range 25–350°C and for various grades of shales ranging from 6 to 100 gal./ton. The thermal diffusivity (α) is seen to decrease with increasing temperature, especially for shales with low organic content. Richer shales, on the other hand, show very little sensitivity in their α values to temperature and grade. The α values measured for Green River oil shales fall in the range 0.1–0.9×10^?2 cm²/sec. Anisotropic effects were also observed for these α values; shales cored parallel to their bedding planes the diffusivities about 20–30% higher than those for the samples cored perpendicular to the stratigraphic planes. The presence of pore water in the shale is also shown to have a significant effect on α.     

A DSC study of benzoic acid: a suggested calibrant compound

It has been found that cobalt(II, III) oxide, Co₃O₄, lowers the thermal decomposition temperature of Na₂S₂O₈ and K₂S₂O₈ by about 25°C by catalysis, and it therefore acts as a P-type semiconductor at high temperature and atmospheric (air) pressure. Also, this oxide reacts at high temperature with sodium or potassium pyrosulfates to form thermally stable sodium cobalt disulfate, Na₂Co(SO₄)₂ and potassium cobalt trisulfate, K₂Co₂(SO₄)₃, respectively. Binary systems, consisting of a 1 : 3 mole ratio (oxide : persulfate), are established as representing the solid state stoichiometric reaction. X-Ray diffractometry is employed to identify intermediate and final reaction products in general. All calculations are based on data obtained from TG, DTG and DTA curves.     

A simple,rapid method for the generation of ligand binding isotherms

Using the protonation of tris(hydroxymethyl)aminomethane (Tris) as a standard reaction, a technique is established for the generation of reaction isotherms by continuous titration in a flow microcalorimeter. The procedure uses an exponential dilution device of simple design that provides a constant internal volume, efficient mixing of the contents and is a closed system. The method has considerable advantages over conventional calorimetric procedures and the precision of enthalpy measurements is estimated to be within ± 2%.     

Thermal energy storage materials — a DSC study

A DSC investigation of a thermal energy storage, first-order phase change system has been carried out. The material is a borax—common salt modified sodium sulfate decahydrate system, distributed throughout a fumed silica supporting matrix. The qualitative features of the thermal behavior of the material can be explained in terms of the phase diagram of the sodium sulfate—water peritectic system, modified by the presence of a low-temperature eutectic. Fusion and recrystallization enthalpies have been measured as a function of cycle number. The thermal conversion efficiency of the system is high. Combining these data with specific heat measurements, the calculated storage capacity is in good agreement with published engineering information.     

Dynamic dielectric analysis. A new thermal analysis technique

Applications of dynamic dielectric analysis (DDA) in studies on the thermal decomposition and phase transformations of solid materials are discussed. Three illustrative examples are presented for (a) a system undergoing a chemical reaction or thermal alteration on application of heat, (b) a system undergoing a crystallographic transformation and (c) detection of moisture in naturally occurring materials. The advantages derived by applying a combination of DDA and a conventional thermal analysis technique such as DTA to studies on thermal processes are demonstrated. It is shown that the information obtained from techniques such as DTA or TG is limited in scope unless used in conjunction with a method which sheds light on the mechanistic aspects of the physical or chemical process of interest.     

An automated technique for thermoacoustimetry of solids

An automated technique for thermoacoustimetry of solids is described. The technique is illustrated by measurements on Green River and Kentucky oil shales.     

Theory and practice of a powerful technique for electrochemical investigation of solid solution electrode materials

The theory and practice of a solid-state electrochemical technique which allows measurement of the chemical diffusion coefficient and partial conductivities of the mobile species in a mixed ionic-electronic conductor, as well as the equilibrium partial thermodynamic quantities, are described. The theory incorporates nonideal thermodynamic behavior of the carriers as well as cross terms in the flux equations. Once the cell is assembled, all parameters can be measured as a function of composition without any further physical manipulation, so that the experiments are well suited to automatic control.     

Automatic microanalyzers: VII. Automatic analyzer for rapid microdetermination of sulfur

A commercially available analyzer for determination of sulfur (0.5–100%) in organic and some inorganic compounds is described. It involves combustion of the sample at high temperature (1050 °C) to form SO₂ and SO₃ in a vertical reactor. SO₃ is reduced to SO₂ and nitrogen oxides to N₂ on copper at 850–900 °C. At this temperature the chemical reactions of SO₂ and copper are minimized so that SO₂ is obtained quantitatively in this range.Use of a vertical reactor and an autosampler makes an easy and complete automation of the sulfur determination possible. With this automation, great improvements are noticed in accuracy and precision over manual methods. The average time for a single determination is about 8 min.     

A theoretical treatment of entropic repulsions by polymers

We consider a simple model of a random flight chain or length S confined between two parallel plates of area A separated by distance L. Adsorption of the polymer at the plate surfaces is neglected. The resulting pressure exerted on the plates due to configurational entropy is always repulsive. We obtain

     

Thermophysical properties of oil shale minerals

The thermal diffusivity values of eight minerals that are commonly associated with oil shales of the Green River formation have been measured by the laser flash technique. Data are presented in the temperature range 25–500°C for quartz, dolomite, calcite, plagioclase, analcite, pyrite, potassium feldspar and low albite. A comparison of the thermal conductivities of some of these minerals, calculated from experimentally measured thermal diffusivity and density, with the experimental values reported in the literature reveals good agreement. Trends in the variation of thermal diffusivity with temperature and anisotropic effects in thermophysical parameters are discussed from the point of view of grain boundary effects in these polycrystalline mineral aggregates.     

A new spot test for nitro compounds

A simple, rapid, and highly sensitive method for the detection of micro amounts of nitro compounds has been developed. Nitro compounds are reduced into corresponding hydroxylamines with zinc dust and acetic acid and coupled with diazonium chloride to give hydroxytriazines which give an intense pink to violet color with diphenylamine in acetic acid medium. Quantities of 0.1 μg or less of nitro compounds can be detected in 0.25 ml of total solution by this method. The method is free from the common interference.     

Determination of trace elements in natural waters by the d.c. argon plasma,multielement atomic emission spectrometer (DCP-MAES) technique

The capabilities and limitations of a commercial direct current argon plasma, multielement atomic emission spectrometric (DCP-MAES) technique for the determination of 18 common elements in water have been evaluated. The results demonstrate that the unit offers acceptable capabilities with respect to selectivity, sensitivity, accuracy, speed, and economy for the determination of many of the elements investigated. Interferences in the determinations of those elements subject to stray light due to the presence of calcium and (or) magnesium can often be compensated for by use of a simple linear correction procedure. A comparison of two-electrode and three-electrode d.c. argon plasma systems has shown that the latter offer advantages such as improved stability and lower background. A comparison with results published for a system based on excitation in an inductively coupled plasma has indicated that the present system offers comparable analytical capabilities for several of the elements investigated.     

Removal of iron interferences by solvent extraction for geochemical analysis by atomic-absorption spectrophotometry

Iron is a common interferent in the determination of many elements in geochemical samples. Two approaches for its removal have been taken. The first involves removal of iron by extraction with methyl isobutyl ketone (MIBK) from hydrochloric acid medium, leaving the analytes in the aqueous phase. The second consists of reduction of iron(III) to iron(II) by ascorbic acid to minimize its extraction into MIBK, so that the analytes may be isolated by extraction. Elements of interest can then be determined using the aqueous solution or the organic extract, as appropriate. Operating factors such as the concentration of hydrochloric acid, amounts of iron present, number of extractions, the presence or absence of a salting-out agent, and the optimum ratio of ascorbic acid to iron have been determined. These factors have general applications in geochemical analysis by atomic-absorption spectrophotometry.     

A Numerical technique for solving carrier-mediated transport problems

A numerical technique and a computer program based on the method of orthogonal collocation on finite elements for solving steady state carrier-mediated transport problems is presented. The method is especially suitable in solving boundary layer type of problems as arise in carrier-mediated transport. The method uses an efficient LU decomposition of a blockdiagonal matrix. A residual criterion is used for the placement of elements which can be easily implemented using an interactive feature in the computer program. Numerical results for three different systems; a system with simple kinetics and equal diffusivities for carrier and its complex, a system with simple kinetics and unequal diffusivities and a system with complex kinetics and equal diffusivities, indicate that the method is very versatile and has very good convergence properties. The method can be used very easily for all these systems by making minor modifications to the computer program.     

A spline-fitted potential surface for bent triatomic molecules

The rotated-Morse curve cubic spline method developed previously is extended to bent triatomic molecules by using 2D cubic spline. The Yates—Lester potential for bent H₃ is shown to be accurately fitted over the entire range of the three internal coordinates, with a standard deviation of less than 1 kcal mol^?1. The spline method compares favorably in computational speed with the analytical potential.     

An unusual technique for the study of nonstoichiometry: The thermal emission of electrons. Results for Y2O3 and TiO2

The thermal emission of electrons is presented as a useful technique for the study of nonstoichiometric oxides at high temperature. Results are reported for yttria and titanium dioxide, very different in their respective properties. For these compounds the density of emitted current follows a simple law, J ∝ P^x_O2, where P_O2 is the oxygen partial pressure and x is a constant that is not dependent on temperature. The electrical conductivity, when measured under the same conditions, follows a similar law. Therefore there is some evidence that at high temperature the chemisorption is not an important process, and the emission characteristics are then discussed in terms of a bulk nonstoichiometry. Data are obtained for yttrium oxide, as the width of the band gap E_g = 5.5 eV, the electron affinity χ = 2 eV. A reasonable defect for this oxide consists of oxygen vacancies V^2·_O and oxygen interstitials O^2′_i. The situation in the case of rutile is much more complicated as this oxide has a wide nonstoichiometric field with several suboxides and a nonisotropic structure. When the deviation to the stoichiometry is low the oxygen sublattice is stable and the main defects are titanium interstitials Ti^4·_i. When the compound is more reduced a surface reorganization then occurs which seems related to a crystallographic transformation leading to the Ti_nO_2n?1 suboxides. This technique give a lot of data on the properties of nonstoichiometric compounds in the vicinity of the surface at high temperature.     

Facilitated transport in spherical shells: application of the combined damköhler number technique

In cell membranes, double emulsion drops, or other particles with spherical shell geometry, reversible carriers may be present which serve to facilitate transport of solutes into the particles. The physical phenomena taking place are both diffusion and chemical reaction. When the reaction deviates from chemical equilibrium, the solution of the conservation equations becomes difficult because the equations are non-linear. The combined Damköhler technique, recently devised by Hoofd and Kreuzer, is a simple analytical method to accurately predict facilitated mass transfer in the presence of non-equilibrium chemical reaction. The application of the combined Damköhler technique to spherical shell geometry gives accurate predictions of the facilitated flux over the full range of Damköhler numbers, when compared to results from a numerical analysis technique. The non-equilibrium facilitated flux depends on the sphericity of the spherical shell.     

A study of variant silicone rubber heart valve poppets by thermogravimetry-differential thermal analysis

Thermal analyses were used to assist in the characterization of forty selected silicone elastomer heart valve poppets which have been implanted in humans for time periods varying from 22 to 79 months. Three distinct types of thermograms were obtained which were related to the amount and general type of constituents absorbed by the poppets during implants. These results are analyzed and discussed in terms of other analytical results from solvent extraction, gas chromatographic and thin-layer chromatographic analyses.