An organic semiconductor electrolyte capacitor and a process for producing such a capacitor having improved loss and impedance characteristics and which can be produced using a simple apparatus and with reduced waste of expensive materials. A dielectric oxide film is formed on the surface of a metal anode, and a solid-electrolyte layer is formed on the dielectric oxide film. The electrolyte layer is made by melting and solidifying a mixture of an isopropylisoquinolinium tetracyanoquinodimethane complex salt and a lactone compound.

Method and device for monitoring an insulating or conducting test fluid for acidity, basicity, contaminants and/or specific chemicals by monitoring the rate of modification, for example corrosion, dissolution or erosion of at least one plate of a capacitive sensor immersed in the fluid. The sensor's dielectric element is inorganic or piezoelectrically active ceramic. Capacitor plates can be different materials, foil or coated/deposited metals modified by the test fluid. Capacitance is measured over time, its change due to modification of sensor plate area is recorded and used to determine quantity of acid, alkali, contaminants and/or chemicals in the test fluid. Piezoceramic dielectric allows the detector to be vibrated. The sensor can be attached to an ultrasonic transducer. Presence of specific chemicals requires a chemically non-reactive and a chemically reactive electrode re the chemical of interest. If the test fluid is conductive, the changed capacitance is measured in an insulating fluid.