Abstract: While modules to be tested in one constant temperature oven are tested by providing a plurality of constant temperature ovens, accommodating a plurality of modules to be tested in each constant temperature oven and connecting the modules to be tested accommodated in a plurality of constant temperature ovens to the measuring instruments via the switches, preparation for testing such as temperature change of the other constant temperature oven is conducted and the modules to be tested in one constant temperature oven are tested using measuring instruments. Thereafter, the switches are changed over and the modules to be tested accommodated in the other constant temperature oven are tested. Thereby, expensive measuring instruments can be used effectively.

Abstract: The specification provides a method for the manufacture of a high-quality optical polycarbonate that contains few inorganic or organic impurities or other microparticles, and that has a superior hue. Specifically, the specification provides a method for the manufacture of a polycarbonate by the melt polycondensation of a bisphenol and a carbonic diester, wherein the molten mixture of a bisphenol and a carbonic diester is filtered with a membrane filter made of a fluororesin, after which melt polycondensation is conducted.

Abstract: A phenol and a ketone are reacted to form bisphenol, and the liquid bisphenol obtained or a mixed solution of said solution and a phenol is filtered through a calcined metal filter to obtain bisphenol which makes it possible to efficiently obtain bisphenol which either does not contain fine particulate impurities or contains such impurities only in minute amounts, and a method for manufacturing polycarbonate using bisphenol obtained by this method. The filtration grade of the calcined metal filter should be 1.0 .mu.m or less. After filtering, the calcined metal filter can be backwashed or chemically washed and then reused. The bisphenol should preferably be bisphenol A.

Abstract: A process for producing a dihydric phenol preferably bisphenol-A consisting of the steps of (1) formulating reaction ingredients of phenol, acetone, recycle bisphenol A, impurities, an acid catalyst and water, (2) reacting the ingredients to form a product mix consisting of bisphenol-A, unreacted phenol, by-products, acetone and water, (3) crystallizing the product mix forming a slurry of bisphenol-A/phenol adduct crystals solid phase, (4) separating the solid phase from the liquid phase by filtration, (5) removing the phenol from the bisphenol-A/phenol adduct to obtain a crude bisphenol-A, and (6) purifying the crude bisphenol by fractional melt crystallization to obtain a bisphenol-A of at least 99.5% purity.