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The acid number (AN) of insulating, transformer, and turbine oils is crucial to ensure safe operation, operating equipment control, and corrosion prevention. These oils generally have low AN specifications and their AN determination by manual color-indicator titration is difficult, especially when analyzing colored samples.

Using a Titrator with a photometric sensor to detect the end point ensures that the titrations are always carried out under the same conditions. This greatly increases the precision and reliability of the results, which in turn results in improved monitoring for your operations.

Here, the fully automated photometric determination of the AN using the Optrode satisfying ASTM D974, ISO 6618, and IP 139 is described. The sample is titrated with alcoholic KOH solution to the p-naphtholbenzein green brown end point. A break point evaluation of the titration curve is used which corresponds with this endpoint.


Metrohm AG

9100 Herisau