GB/T 7598-2008Determination of water-soluble acid in transformer oils in service (English PDF)

4.1

double distilled water or demineralized water, after boiling, pH 6.0 to 7.0, a conductivity of less than 3µs/cm (25 °C).

Potassium hydrogen phthalate 4.2. reference reagents.

4.3 potassium dihydrogen phosphate

reference reagents.

4.4 Sodium hydroxide

AR.

4.5 hydrochloric acid

AR, relative density of 1.19.

4.6 sodium phosphate dibasic anhydrous

pure class distinctions.

4.7 pH indicator

bromocresol green, bromocresol purple. Its preparation method and the color range are shown in Table 1.

Table 1 formulated indicator

Name indicator color range method of preparation

Bromocresol Green

3.8 to 5.4

Yellow - Blue

0.1g of bromocresol green and 7.5mL0.02mol/L sodium hydroxide together research absorbed, diluted with demineralized water to

250mL, then 0.1mol/L sodium hydroxide or hydrochloric acid to a pH of 4.5 to 5.4

Bromocresol purple

5.2 to 6.8

Yellow - purple

0.1g of bromocresol purple was dissolved 9.25mL0.02mol/L sodium hydroxide, diluted with demineralized water to

250mL. Then 0.1mol/L sodium hydroxide or hydrochloric acid to a pH of 6.0

Than 4.8 Color tube. a plug, a diameter of 15mm, capacity 10mL.

4.9 conical flask

250mL.

4.10 separatory funnel

250mL.

4.11 cylinders

50mL.

4.12 thermometer

0 °C ~ 100 °C.

4.13

water bath.

Color box than 4.14. see Figure 1.