High-purity Substances Research Articles

Specific Heat Capacity at Constant Volume for {xNH3 + (1 − x)H2O} at Temperatures from 300 to 520 K and Pressures to 20 MPa

Specific heat capacities at constant volume (cV) of {xNH3 + (1 − x)H2O} (x ≈ 0.7, 0.8, 0.9) mixtures were measured with an adiabatic calorimeter. Temperatures ranged from 300 K to 520 K, and pressures ranged from 3 MPa to 20 MPa. Measurements were conducted on single-phase liquid and compressed gaseous samples. The mixtures were gravimetrically prepared from high-purity substances and verified by chemical analysis. Density was reported for initial and final end points during each calorimetric experiment. The principal sources of uncertainty are the temperature rise measurement and the change-of-volume work adjustment. The expanded relative uncertainty (with a coverage factor k = 2 and thus a 2-standard-deviation estimate) for cV is estimated to be 1% for liquid phase and 4% for gaseous results, and for density it is 0.2%.

Mass-Transfer Efficiency of a Small-Size Teflon Bubble-Cap Tray

The combined effect of flow conditions, geometry and physical properties on distillation efficiency of a newly constructed small-size Teflon bubble-cap tray for production of high-purity substances is experimentally investigated. The limits of vapour loading required for a steady hydrodynamic tray operation are found. The results evidence an influence of the liquid entrainment on plate efficiency at elevated superficial vapour velocities and higher downcomers. The comparison of the plate efficiency values determined experimentally with those from different correlations for large columns shows that the equation of MacFarland et al. and the point AIChE theoretical method are the best for predicting mass-transfer efficiency of the small-size bubble-cap Teflon tray used.

Permanent working collection of high purity substances

The work of the collection of high purity substances in the research on the composition of impurities in high purity substances is evaluated. On the basis of the materials available, the present state and future perspectives of the study of high purity substances are discussed.

Development of Cryogenic Sealed Cells as Temperature Standards: Their Filling System and the Purification of CO2

Design considerations for the NRC sealed cryogenic triple point cells are discussed, together with their filling system. The versatility of the filling system is illustrated by the purification of CO2. Finally, it is shown that the effects of residual impurities upon the realized liquidus points of high-purity cryogenic substances may be demonstrated by observing the dependence of the liquidus points on the fraction of sample condensed.

Determination of the kinetic coefficients of crystallization of pure substances

We consider a method of determining the kinetic coefficients of crystallization of high-purity substances from the temperature curves of the phase transition in long cylindrical crucibles. The method is appplicable to the determination of the kineticc coefficient at low crystallization rates. Formulas are derived for finding the kinetic coefficients and calculating their values for gallium, bismuth, zinc, antimony, and aluminum, using the available experimental data from the literature. These values are valid in the range of crystallization rates from 10−8 to 10−6 m/sec.

A “rod-flame” system in direct laser enhanced ionization analysis of high-purity substances

Laser enhanced ionization in conjunction with electrothermal microsample evaporation from a heated graphite rod into the flame has been used for the direct analysis of high-purity germanium and CdHgTe alloys. Methods for determining microquantities of copper in germanium and indium in these alloys have been developed. Samples in the form of both solutions and powders of 1–20 mg in weight are used. The interferences of the sample matrix in the two cases are shown to be small and consist of additive ionization background. The detection limit for indium in the CdHgTe solutions is as low as 10 −4 μg g and with the solid samples it can be reduced to 10 −6 μg g . For determinations of copper in germanium, the detection limit is higher since it is limited by the rod material purity. The germanium and CdHgTe samples are analysed using the standard addition and calibration curve methods. A good correlation of the results obtained for the solutions and powders through calibration with aqueous standard solutions indicates that the approach proposed in this work ensures direct analysis of the solid and liquid samples with a high accuracy.

ChemInform Abstract: The Analysis of Solid and Liquid High‐Purity Substances

This paper reviews the problems of atomic-spectrometry, mass-spectrometry and activation methods in elemental analysis of high-purity substances. The specific techniques of sample preparation, preconcentration of impurities and the determination of gas-forming trace elements are discussed.

The analysis of solid and liquid high-purity substances

This paper reviews the problems of atomic-spectrometry, mass-spectrometry and activation methods in elemental analysis of high-purity substances. The specific techniques of sample preparation, preconcentration of impurities and the determination of gas-forming trace elements are discussed.

Atomic-absorption methods for analysis of high-purity substances

A review is given of the use of atomic-absorption methods for determining the trace impurities in high-purity metals.

Substoichiometry in radioanalytical methods.

The review is devoted to the developments of radioanalytical methods in USSR. Much attention is paid to applications of substoichiometry in isotope dilution and radioactivation analysis for determination of trace elements in high purity substances and for environmental analysis

Preconcentration in inorganic trace analysis

Abstract

Application of a ring-cavity graphite furnace for atomic absorption of high purity substances

Application of a ring-cavity graphite furnace for atomic absorption of high purity substances

Activation analysis of high-purity substances by means of short-lived isotopes

A non-destructive activation analysis method intended for industrial utilization is described, using isotopes with half-lives from 2 sec to 20 min. Expected sensitivity values for 33 elements are listed. The effects on the results of neutron flux variation and other errors of measurement are discussed. Requirements to be met by the electronic spectrometer apparatus are stated.

Differential scanning calorimetric assessment of high purity

The value and limitations of differential scanning calorimetry in the assessment of high-purity substances has been examined. In favorable cases, good agreement has been secured for polycyclic hydrocarbons between DSC purity values and GC assay values. For some halogenated benzoic acids, used as microanalytical reference standards, good agreement has been obtained between DSC purity values and acid—base titration results. DSC studies on cholesterol and urea, which have limited thermal stability, are presented. With the available instrument and technique, the practical upper limit of absolute DSC purity values may be 99.95 mole%, although higher numerical values can be obtained. Because the DSC technique is “blind” to equilibrium solid solution formation, DSC values should not be used as a sole criterion of purity; this recommendation is of special importance for compounds purified by fractional solidification processes.

Preparation of high purity substances

Preparation of high purity substances