Abstract: An apparatus for ascertaining the alcohol content or the calorific value of a mixture containing alcohol and gasoline includes an electrically conductive housing through which the mixture flows and in which at least one physical parameter of the mixture is measured to produce a measurement. An electronic measuring circuit is disposed in the housing for evaluating the measurement. The housing has a wall with a part of the wall forming a first electrode of a capacitor. An intermediate plate is associated with the housing. An electrically conductive sensor element is secured in the intermediate plate and partly surrounded by the mixture. The electrically conductive sensor element forms a second electrode of the capacitor and forms an electrical connection between the second electrode and the measuring circuit.