Solubilities of pure naphthalene, pure phenanthrene, and a mixture of naphthalene and phenanthrene in supercritical CO2 were measured in the temperature range from 308 to 338K to obtain fundamental data for purification of polycyclic aromatic compounds using the retrograde crystallization technique.As a result, it was found that (1) the crossover region of supercritical CO2-naphthalenephenanthrene system was wide enough to isolate either solid component from the mixture, (2) the Peng-Robinson and Soave-Redlich-Kwong equations of state well represented the solubilities of pure solids in supercritical CO2, and (3) the equations of state gave a fairly good estimated solubility of the more soluble component but poor estimated solubility of the less soluble component for the solid mixture.

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It is essentially important to remove the dissolved oxygen (DO) in the ultrapure water for the future ultralarge scale integration (ULSI). We have found the existence of the big driving force for the oxygen diffusion through tube materials that increases the DO concentration. The DO concentration through the perfluoro alkoxide (PFA) tube rapidly increased with decreasing the flow rate of the ultrapure water. On the other hand, the DO concentration through the polyvinyliden fluoride (PVDF) tube that is a low oxygen permeability material did not increase with decreasing the flow rate. Based on this finding, we have developed the nitrogen gas bubbling deaerator made of PVDF as a point of use purifier. In this system, the residual DO concentration reached 0.2 ppb at a gas-liquid ratio of 1.2 m3/m 3 at each bubbling tower that is ten times smaller than the previously reported one. Furthermore, other contaminations in the ultrapure water do not increase after this process.

A measurement technology for trace impmrities in hydrogen chloride (HCI) was developed in relation to future ultralarge scale integration (ULSI). We developed an electrical conductivity measurement system for analyzing liquified HCI with an in-line high pressure cell. The detection limit of this measurement system is 1.0 x I0-~ S/cm, and the external leak rate of the cell is below 1.5 • I0-" Torr . liter/s. The apparent temperature coefficient of the electrical conductivity is negative in the range from -12 to 20~ at constant pressure, which is caused by a decrease of the density of HCI with increasing temperature. The real temperature coefficient of the electrical conductivity is positive at constant density. We observed differences in the electrical conductivity of HCI at different lapsed times after filling and between different gas sources. An electrical conductivity of 5.5 • i0 70 S/cm was obtained by repeated liquifaction of HCI at a pressure of 41 kg/cm 2 and 15~