The present invention relates to a process for producing a bis compounds, characterized by nitrating a bis compound wherein two phenyl groups are bonded to each other directly or through an electron-donating bridging group, sulfoxide group, sulfone group or carbonyl group in an inert solvent using nitric acid under the condition of substantially free from any other acid. The electrostatic induction power generator further includes an electret provided on the first base body, and a first electrode and a second electrode provided on the second base body. The control signals for the various elementary capacitors are generated independently so as to vary the overall capacitance of the capacitor by independent variation of the capacitances of each elementary capacitor.