Honeywell Understanding Platinization and Its Importance for Conductivity Cells

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Platinization and Platinum Black

5. Platinization and Platinum Black

Only the electrodes having constants from 5 to 50 must be replatinized if the velvety-black deposit has been rubbed off the electrodes in service or in cleaning, or if platinized electrodes are recommended and this black deposit is not present when the cell is received. Always replatinize if a brush was used in cleaning the electrodes. The indication of a need for replatinization of the electrodes is a long term drift of the measuring instrument caused by an apparent increase in cell constant as the platinum black coating is depleted from the electrode surfaces. The electrodes of the high constant cells are not visible since they are located near the middle of the flow channels. Therefore the need for platinization is only indicated by the effect on the measuring instrument. Do not platinize cells intended for measuring high purity water.

Before platinizing, clean the cell with detergent and brush as described in Section 4.1.

Support the cell in a cylindrical vessel with the end of the cell raised from the bottom. It is not necessary to remove the cell from the fittings for platinizing. However, the guard tube must be removed from the low constant cells. Pour in platinizing solution (p/n 31103011) to a level above the cross-channel.

To platinize the 5, 10, 20, 25 and 50 constant cells, immerse an auxiliary platinum electrode* in the solution to a point about midway between the cross-channel or tube hole and the open end of the cell. Both electrodes of the cell are platinized simultaneously by connecting the negative terminal of the battery (see Table 4.2 for voltage) to both leadwires of the cell.

ATTENTION

*This third electrode should be chemically pure platinum. Its shape is unimportant. It may be one of the electrodes in another conductivity cell or a platinum strip, sheet, rod, wire, etc.

Connect the positive terminal of the battery to the auxiliary platinum electrode. Note the time in seconds listed in Table 4.2. During the platinizing operation, move the cell up and down gently to keep the solution stirred. Then disconnect the battery and remove the cell. Rinse the cell thoroughly in tap water and then rinse in distilled water.

Pour the platinizing solution back into its container as it may be used a number of times.

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4909 CPVC Conductivity Cell Insertion/Removal Assembly– Operations Manual

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Contents 70-82-25-19 Rev 7/99 Revision 1- 7/99 Copyright, Notices, and TrademarksContacts AbstractRevision Notes ReferencesOrganization Telephone Address Honeywell TAC Voice Contents Platinization and Platinum Black Figures Page Introduction Overview4908 Conductivity Cell 31074357 Removal Device Temperature/Pressure* RangeValve NPT Plug Conductivity Cell Conductivity Cell Adapter Set Screw #6-32 Binding Head Page Specifications Specifications and Model Selection GuideModel Selection Guide Integral Automatic Temperature CompensationLeadwire WeightSelection Table VII Options Considerations InstallationRequirements Location and PositionPrepare Assembly Initial PrepMounting into the Process Insertion Electrical Connections RemovalRED White Green Maintenance and Replacement Parts To Clean The CellReplacing Removal Device Parts Replacement Parts Replacement PartsVoltage and Time Limits for Platinizing Cells Platinization and Platinum Black RED Green Direct Cell to Analyzer Installation #2 TempNote 5 Compensator Page Page Industrial Automation and Control