Siemens Aktiengesellschaft

Ulrich Gebhardt

Gunter Luft

Konrad Mund

Gerhard Richter

Rainer Leuschner

Matthias Lipinski

Manfred Waidhas

Martin Edeling

Raghavendra Rao

Discharging the reaction water from the novel PEM fuel cells does not require humidification of the reaction gases or an increase in the gas pressure. This is attained in that a hydrophobic layer on the cathode side is used which has a smaller pore size than the layer on the anode side. The reaction water is removed via the anode during the operation of the fuel cell.

Method of discharging reaction water in PEM fuel cells and fuel cell for carrying out the method

For determining the urea concentration in liquids in continuous operation, with a high sensitivity and reliable determination of the urea content over an extended period of time, an electrode which is separated from the urea containing liquid by means of a diaphragm with a diffusion coefficient of less than 10.sup.-7 cm.sup.2 s.sup.-1 for urea has impressed on it potentiostatically and cyclically, two potential values, the more positive potential being between 0.9 and 2.0. V/H.sub.2 rev, and the more negative potential being lower than 0.6 V/H.sub.2 rev, and at the more positive potential, the current flowing within a predetermined time interval is evaluated as the measuring signal.

Apparatus for urea analysis

Porous vitreous carbon with good electrical and mechanical properties as well as large double-layer capacitance can be produced by hardening and pyrolysis of thermosetting carbonizable resins including about 1 to 10 weight-percent of a salt of a fatty acid having about 10 to 20 carbon atoms which is soluble in the resin and can be volatilized without residue.

Method for the manufacture of porous vitreous carbon

For determining the urea concentration in liquids in continuous operation, with high sensitivity and reliable determination of the urea content over an extended period of time, an electrode which is separated from the urea containing liquid by means of a diaphragm with a diffusion coefficient of less than 10.sup.-7 cm.sup.2 s.sup.-1 for urea has impressed on it potentiostatically and cyclically, two potential values, the more positive potential being between 0.9 and 2.0. V/H.sub.2 rev and the more negative potential being lower than 0.6 V/H.sub.2 rev, and at the more positive potential, the current flowing within a predetermined time interval is evaluated as the measuring signal.

Method for urea analysis

A method for determining the concentration of sugar in the presence of interfering foreign substances, by means of a test electrode with a membrane placed in front of it, the electrode being contained in an electrocatalytic sugar sensor, whereby the test electrode is set potentiostatically to a reactivation potential and to a test potential and the current flowing during the set test period is evaluated as a test signal. The invention formulates a method such that with varying concentrations of urea a sensitive determination of sugar concentration which is reliable over a long term is achieved. The invention discloses the method which includes the step that after the reactivation potential and prior to the test potential a third potential that is more negative than the test potential is applied to the test electrode. The technique proposed in the invention is particularly appropriate for the determination of the concentration of glucose in body fluids.

Method for determining sugar concentration

A method for determining the concentration of sugar in the presence of interfering foreign substances, particularly for determining glucose in a body fluid, by means of an electrocatalytic sugar sensor which has a measuring electrode in which the measuring electrode is alternatingly set potentiostatically to a reactivation and a measuring potential and the current flowing during the measuring period is evaluated as the measurement signal. To prevent foreign substances from exerting an interfering influence and thereby permit a sensitive sugar determination which is reliable over an extended period of time, a hydrophilic diaphragm is arranged in front of the measuring electrode to impede the resupply of the interfering foreign substances to the measuring electrode so that a diffusion limit current adjusts itself during the reactivation phase in the oxidation of the foreign substances; and the current is evaluated with a time delay relative to the start of the measuring period.

Method for determining the concentration of sugar using an

A method for the manufacture of electrodes for electrochemical cells, is provided in which a Raney rare-metal catalytic layer is disposed on a metallic support structure in layer form. According to the invention, the Raney rare-metal catalytic layer is prepared by dissolving the inactive component of a layer, disposed on the support structure, of a homogeneous alloy of at least one of the metals of the platinum group of the periodic system of the elements as the active component and at least one of the metals of the iron group of the periodic system of the elements as the inactive component; the content of inactive component being at least 65 atom-percent.

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Langensendelbach, Germany

Ulrich Gebhardt