Abstract: Provided are a method of measuring a degree of degradation of a lubricating oil and a measuring device therefor, in which (a) acidity is measured through use of an ISFET of hydrogen ion sensitive type and (b) dielectric constants or electrostatic capacitances at two or more different frequencies are obtained, to thereby determine a degradation state of the lubricating oil based on the acidity and a plurality of values of the dielectric constants or the electrostatic capacitances. Accordingly, the degree of degradation of the lubricating oil can be measured easily and precisely and a degradation mechanism of the lubricating oil can be predicted.

Abstract: A polycarbonate prepolymer for solid state polymerization, which is produced by an oxidative carbonylation reaction of an aromatic dihydroxy compound, a monohydric phenol having a boiling point of 330° C. or below, carbon monoxide and oxygen, the polycarbonate prepolymer being characterized by that (a) a ratio of aryl carbonate groups and hydroxyl groups each constituting terminal groups of the prepolymer is from 2:8 to 8:2, and (b) a molecular weight distribution (Mw/Mn) is from 1.1 to 2.1; and a process of producing polycarbonates including a step of solid state-polymerizing the prepolymer so as to increase the molecular weight thereof. According to the present invention, the prepolymer having a controlled molecular weight distribution suitable for solid state polymerization is provided, and a high quality polycarbonate is efficiently produced in environmentally friend manner.