Abstract: A probe for measuring the concentration of an alcohol, such as ethanol, in a liquid, such as water. The probe according to the invention has a membrane that is permeable for vapors of the alcohol but substantially impermeable for the liquid; a measuring chamber having an open end closed against the liquid by the membrane is provided and has an inlet and an outlet; a pump or other pressure means serves to feed a purge gas, such as air, via the inlet into and out of the measuring chamber; a valve is provided near the inlet for controlled passage of the purge gas through the chamber; a suitably dimensioned detector including a pellistor or a gas-sensitive resistor is arranged in the measuring chamber for quantitative detection of the alcohol and for generating an electrical signal in proportion with the detection.

Abstract: A method of determining a specific thermal conductivity parameter of a target gas having a known general thermal conductivity and being contained at a concentration of interest in a fluid medium (F) and comprising: contacting said fluid medium with an organic polymer membrane (11) provided at an interface between said fluid medium (F) and a sensing volume (12) containing a thermal conductivity sensor (13); the membrane (11) is substantially impermeable for any liquid components of the fluid medium (F) but has a known permeability for the target gas; the sensing volume (12) is periodically purged or flushed with a gas having a general thermal conductivity that differs from the thermal conductivity of the target gas; permeation of the target gas through the membrane (11) into the sensing volume (12) is permitted intermittently; at least one time-dependent parameter of the known general thermal conductivity of the target gas that has permeated into the sensing volume (12) is measured; and a parameter of analytic