Siemens’ Differential Voltameter

A volume or gas voltameter with duplicate eudiometers and pairs of electrodes. It is used for determining the resistance of the platinum conductor used in his pyrometer. A current divides between the two voltameters; in one branch of the circuit the platinum conductor is placed, in the other a known resistance. The current strength varying inversely with the resistance, the resistances of the two conductors are inversely proportional to the gas evolved.