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Gas-liquid chromatography (GLC) was used to study the complex solution thermodynamics of concentrated solution of an important water-soluble polymer, polyethylene oxide (PEO). Experimental data from 70°C to 150°C at essentially atmospheric pressure are presented when the solute in PEO solution is at both infinite-dilution and finite concentration. The infinite-dilution volatilites of 14 organic solutes and water in PEO were obtained at each temperature. Activity coefficients of benzene in PEO were also obtained at temperatures from 70°C to 150°C over the polymer concentration range 90 to 100 weight per cent. The corresponding-states theory of polymer solutions initiated by Prigogine and developed by Flory and Patterson was used to correlate our experimental results. Excellent agreement was obtained. Comparison of our infinite-dilution results with the earlier work of Cheng and Bonner (1974) shows some discrepancy. The discrepancy is ascribed to differences in column preparation used in the work of Cheng and Bonner (1974) and in this work. In this work, we account for the effect of PEO degradation of GLC results.

Measurements of electrical properties using the Van der Pauw technique have been made on the n-type and p-type silicon carbide single crystals and epitaxial layer having resistivity from 10-3 to 102 ohm-cm. Experiments on the selection of measuring conditions and comparison between the Van der Pauw method and the conventional method have been performed. It is found that the magnitude and stability of contact resistance greatly affect the measuring results. Among the pressure contacts studied, indium contact has the lowest contact resistance, while copper, tin, and phosphor-bronze contacts must be electrically formed before use. With different electrode materials and sample currents, the deviation of values obtained is about 2%. It is suggested that the sample current should be chosen in accordance with the resistivity and contact resistance of the specific sample. As compared with the conventional method, the Van der Pauw method can give higher precision and reproducibility. High temperature electrical properties of silicon carbide single crystals have been measured in a temperature range from room temperature to 1000°K, and the ionization energy of nitrogen donors is found to be 0.056 eV. Anomalous phenomena that result in experimental errors and their origins are discussed.