This method is suitable to measure acid with water-solubility and alkali with water-solubility of dielectric oil and steam turbine oil.

1. Summary of method:

Mix with isometric distilled water and shake it. Take out its extracted liquid from water and inject indicator, observe its color changing situation, and judge whether acid with water-solubility or alkali with water-solubility is contained in the oil for trial.

2.Instrument

(1) Separating funnel: 250-500mL

(2) Test tube：d：15-20mm     h：140-150 mm

(3) Water bath

(4) Conical flask 250mL

3. Reagent

(1) The methyl orange is matched to be 0.02% of aqueous solution

(2) The phenolphthalein is matched to be 1% of ethanol solution    

4.Test procedures

(1) Pour 50mL of oil for trial heated to 70-80℃ and 50mL of the distilled water with the same temperature (distilled water, with PH value between 6.0 and 7.0 after boiling) into the same separating funnel and shake it for 5 min. Test after cooling them to the indoor temperature by layering. 

(2) Put 10mL of extracted liquid from water in two test tubes respectively. Add 2 drops of phenolphthalein indicator in a test tube. If the extracted liquid becomes red or rosy, the oil for trial is indicated to contain alkali with water-solubility. Add 2 drops of methyl orange indicator into the second test tube. If the extracted liquid becomes red or orange red, it is indicated that acid with water-solubility is contained in the oil for trial. Meanwhile, add 10mL of distilled water and 2 drops of methyl orange indicator into the third test tube for comparison. 

(3) With regard to phenolphthalein indicator, if the color doesn’t change, it is indicated that there is no alkali with water-solubility in oil. If the color of methyl orange doesn’t change, it is indicated that there is no acid with water-solubility in the oil for trial.      

Notes: It is allowed to pour 50mL of oil for trial and 50mL of distilled water together into the conical flask, and stir them immersing in the water with 70-80℃ of temperature for 5min unceasingly. Take out the extracted liquid from water for experiment.