PURPOSE: To measure the quantity of moisture in gases by lowering the tmperature of the gases in a container to a level, at which the moisture condenses, to measure the gas pressure at that time.

CONSTITUTION: A needle pipe 8 is closed, and a cution bottle 7 is held at a temperature T1 by means of a heating bath 15. When the temperature becomes constant at level T1, a thermometer 10 is observed to record the temperature T1 of the flue discharge gases. Then, a valve 9 is opened. The dpressure in the discharge gases sucked into the suction bottle 7 is transmitted through a cock 9 and the gases in the measuring tube 12 to a manometer 11 so that this manometer is observed to read out the pressure P1 at that time. The volume V1 of the discharge gases is equal to the capacity of the bottle 7 when the needle pipe 8 and the cock 9 are closed. The, the bath 15 and a cooling bath 16 are interchanged to cool the bottle 7 to a temperature T2. The thermometer 10 is observed to record the temperature T2 of the discharge gases, and the manometer 11 is also observed to read ot the pressure P2' at that time. Thus, the moisture x% in the discharge gases is obtained.