This method is suitable for the determination of water-soluble acids in insulating oil and steam turbine oil
1. Summary of method
Mix and shake equal volumes of distilled water and test oil at 70~80°C, take its water extract, and measure its pH value with an acidity meter
2. instruments
⑴ PH meter
⑵ Separating funnel
⑶ Erlenmeyer flask
⑷ Pipette
⑸ beaker
⑹ volumetric flask
⑺ thermometer
⑻ Water bath
3. Reagents
⑴ Potassium hydrogen phthalate
⑵ potassium chloride
4. Preparations
⑴ Prepare potassium hydrogen phthalate standard solution: weigh potassium hydrogen phthalate that has been dried at 110-120°C in advance. Put it in a beaker, dissolve it with an appropriate amount of distilled water, transfer it into a volumetric flask, and dilute it to the mark with distilled water. The pH value of this solution is 3.97, which is used for the positioning of the acidity meter.
⑵ Glass electrode: soak in distilled water before use, and the soaking time must be more than 24 hours before use.
⑶ saturated potassium chloride solution
⑷ Zero point adjustment and positioning: adjust and position according to the instrument manual
5. Test steps
⑴ Measure the test oil, inject it into the Erlenmeyer flask, add an equal volume of pre-boiled distilled water, heat it to 70~80°C in a water bath, and shake it for 5 minutes
⑵ Pour the liquid in the Erlenmeyer flask into the separatory funnel, and after layering and cooling to room temperature, pour 30~40ml of water extract without oil into the 50ml beaker, and measure its pH value with a pH meter
6. Precision
The difference between the two results of the parallel determination should not exceed 0.05pH
Note: The pH value measured with a pH meter is about 0.2 higher than the result of visual colorimetric determination