Voltameter, Differential, Siemens'.
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.
Voltameter, Gas.
A voltameter whose indications are based on the electrolysis of water,
made an electrolyte by the addition of sulphuric acid. The gases evolved
are measured. It may take several forms.
In one form it is an apparatus consisting of a single eudiometer or
graduated glass tube with upper end closed and its lower end or mouth
open, collecting the mixture of hydrogen and oxygen.
In the form shown in the cut three tubes are connected, the side tubes
representing eudiometers. For each side tube there is a platinum
electrode. In this apparatus the oxygen and hydrogen are connected in
opposite tubes. A is an open tube filled with dilute sulphuric acid. By
opening the cocks on B and C they can both be completely filled with
acid. As shown in the cut, this operation is not yet completed. The
hydrogen alone may in this case be measured.
The mixed gas voltameter has only one eudiometer.
The exact equivalents are only approximately known. The volume of mixed
gases per coulomb is given as .1738 cubic centimeters (Ayrton); .172
cubic centimeters (Hospitalier); and other values by other authorities.
The hydrogen is equal to 1/3 of the mixed gases almost exactly.
Synonyms--Volume Voltameter--Sulphuric Acid Voltameter.
The gas is measured at 0º (32º F.) and 76 centimeters, or 30 inches
barometer.
Fig. 341. GAS VOLTAMETER.