Electrochemical Measuring Cell for Measuring the Content of Chlorine Compounds in Water

Abstract

The invention relates to an electrochemical measuring cell for measuring the content of chlorine compounds in water, having an electrolyte chamber (2) which receives an electrolyte, a measuring electrode (3) which delimits the electrolyte chamber, a reference electrode (5), and a counterelectrode (4). Said electrochemical measuring cell is characterised in that the measuring electrode (3) is a rigid, porous platinum membrane having a pore size of 0.15 m to 0.25 m, which produces the contact with the electrolyte and the water.

Claims

1.-5. (canceled)

6. An electrochemical measuring cell for measuring the content of chlorine compounds in water, the measuring cell comprising: an electrolyte chamber receiving an electrolyte; a measuring electrode delimiting the electrolyte chamber; a reference electrode arranged within the electrode chamber; a counter electrode arranged outside of the electrolyte chamber; wherein the measuring electrode is a rigid porous platinum membrane comprising a pore size of 0.15 m to 0.25 m, wherein within the rigid porous platinum membrane a physical and an electrical contact between the water to be tested and the electrolyte is taking place.

7. The electrochemical measuring cell according to claim 6, wherein the pore size amounts to 0.2 m.

8. The electrochemical measuring cell according to claim 6, wherein the counter electrode contains platinum.

9. The electrochemical measuring cell according to claim 6, wherein the counter electrode is a platinum ring surrounding the electrolyte chamber.

Description

[0013] The invention has the object to provide an electromechanical measuring cell for measuring the content of chlorine compounds in water in which it is possible to eliminate a flexible hydrophilic membrane that is as thin as possible in order to avoid the afore described risks or disadvantages when handling and cleaning the measuring cell, without negatively affecting future measuring results.

[0014] This object is solved according to the invention by the features of the characterizing portion of claim 1, wherein the measuring electrode is a rigid porous platinum membrane that produces a contact with the electrolyte and with the water and has a pore size of 0.15 m to 0.25 m. The porous platinum membrane that at the same time forms the measuring electrode serves to prevent the water to be tested from entering the electrolyte chamber which receives the electrolyte and to have the reaction take place in the pores of the platinum membrane and to measure the generated reaction products directly as they are generated.

[0015] The water to be tested flows past the measuring cell and comes into contact with the electrolyte only within the electrode pores and membrane pores.

[0016] The measuring cell according to the invention is one for amperometric, potentiostatic measurement of chlorine compounds.

[0017] Preferred embodiments of the invention are disclosed in the dependent claims.

[0018] In the measuring cell according to the invention, the membrane and the measuring electrode are combined in one component. The microporous platinum membrane separates the electrolyte chamber from the water to be tested so that active ingredients of the electrolyte and of the substances to be measured of the water meet in the pores of the measuring electrode, react therein, and the formed reaction product is detected.

[0019] Combining the two functions (membrane and measuring electrode) in one component eliminates the prior problems of the pressure effect and of the flow effect and optimizes the diffusion problem. Since a rigid component that is fixedly installed and must not be exchanged is provided, the new measuring cell is mechanically robust and does not entail the risk that the user by faulty exchange of expendable parts will endanger the measurement.

[0020] Since the electrolyte is in contact with the water only through the rigid platinum membrane, washing out the electrolyte is substantially precluded.

[0021] The contact surface area electrolyte/water in the porous membrane is multiple times greater than in conventional membrane sensors, the obtained signal is strong and requires no pre-amplification. The measuring cell can therefore be constructed in the form of the 12 mm glass sensors that are conventional for water-analytical measuring cells and can be installed by means of its typical PG13.5 thread in typical pH instruments or redox instruments.

[0022] The measuring cell is manufactured of glass and therefore insensitive relative to most ingredients of water, such as e.g. surface active agents.

[0023] The combined embodiment of membrane and measuring electrode in the form of a porous platinum has the advantage that the measuring cell remains clean and active for a long period of time. The measuring cell according to the invention can be used without problems in applications in which no disinfecting agent is present for extended periods of time.

[0024] Platinum electrodes are used, for example, in fuel cells. In this context, only the surface enlargement is utilized in order to lower material costs. The known platinum electrodes also do not serve in particular for amperometric measurement but only for substance conversion.

[0025] Porous platinum electrodes that are used for measurement and in which substances pass through the membrane pores are found, for example, in lambda sensors that are used for regulating the air supply in exhaust gas catalysts. In this context, this however does not concern amperometric measurements but redox measurements.

[0026] The measuring cell is comprised according to the drawing of a 12 mm glass housing 1 having attached at its bottom end the measuring electrode 3 in the form of a rigid microporous platinum membrane with a pore size of 0.15 m to 0.25 m, preferably 0.2 m. In the interior of the housing 1, there is the reference electrode 5 and the electrolyte chamber 2. In the shaft-like housing 1, a platinum ring as a counter electrode 4 is attached. At the top end of the housing, there is a connecting head 6 for connecting to a measured value evaluation unit.

[0027] The porous platinum membrane of the measuring electrode 3 leads to an intimate contact between the electrolyte and the substance to be measured in the pores of the platinum membrane 3. The resulting product is detected at the measuring electrode 3 and reduced in this context. This leads to a current flow that is proportional to the concentration of the substance to be measured.