YB/T 4019-2020Determination of chemical activity of light calcined magnesia (English PDF)

3.5.2 Calibration: Accurately weigh 3 portions of 0.8168 g of potassium hydrogen

phthalate (3.3) that have been dried at 105°C~110°C for 2 h and cooled to room temperature. Respectively place them in 400 mL beakers. Add 200 mL of boil cooling water. Stir to make them dissolved. Then add 3 drops of phenolphthalein indicator (3.4).

Use sodium hydroxide standard solution (3.5.1) to titrate to reddish, which shall be the end.

The concentration of sodium hydroxide standard solution is measured by the amount of substance concentration CNaOH. The value is expressed in mol/L. Calculate according to formula (1):

Where, m - The numerical value of the mass of the weighed potassium hydrogen phthalate, in grams (g);

V - The numerical value of the volume of the consumed sodium hydroxide standard solution (3.5.1) to titrate potassium hydrogen phthalate, in milliliters (mL);

204.2 - The numerical value of the molar mass of potassium hydrogen phthalate, in grams per mole (g/mol).

Take the average value as the calculation result. Round to four significant figures.

3.6 Citric acid standard solution (0.07 mol/L)

3.6.1 Preparation: Weigh 14.71 g of citric acid, to the nearest of 0.0001 g. Place in a

400 mL of beaker. Add 200 mL of water to dissolve. Transfer to a 1000 mL volumetric flask. Use water to dilute to the scale. Mix well. Store in a refrigerator. It shall be valid for 1 month.

3.6.2 Calibration: Weigh 3 portions of 50.00 mL of citric acid solution. Respectively

place them in 400 mL beakers. Add 200 mL of distilled water. Add 3 drops of phenolphthalein indicator (3.4). Use sodium hydroxide standard solution (3.5.1) to titrate to reddish, which shall be the end.

The concentration of the citric acid standard solution is calculated by the substance

4.12 Glass weighing bottle: Phi35 mm × 70 mm.

5.2 Sample preparation

5.2.1 Crush lumpy laboratory samples to less than 6.7 mm. Use a sample divider or quartering method to divide to about 100 g.

5.2.2 Crush the divided sample to less than 0.5 mm. Then reduce to about 20 g. Process into specimens with a particle size as small as 0.045 mm or 0.125 mm.

5.2.3 The powdery laboratory sample is directly reduced to about 100 g. Pass through a 0.045 mm sieve (320 mesh) or a 0.125 mm sieve (120 mesh). Then reduce to about

20 g.

5.2.4 The specimen shall be dried at 105°C~110°C for 2 h before analysis. Then cool to room temperature in a desiccator.

6.1 Determination of chemical activity of light calcined magnesia by citric acid

neutralization method

6.1.1 Method summary

A certain amount of light calcined magnesia reacts with citric acid solution. Measure the activity of light calcined magnesia according to the length of reaction. A short reaction time indicates good activity while a long reaction time indicates poor activity.

6.1.2 Determination steps

6.1.2.1 Specimen size

Weigh about 1.700 g of specimen, to the nearest of 0.0003 g.

6.1.2.2 Determination quantity

During the determination, two specimens shall be weighed for parallel determination.

6.1.2.3 Determination

Place the specimen (6.1.2.1) in a dry 300 mL beaker. Put in a stir bar. Place on a magnetic stirrer with constant temperature of 40°C. Immediately and quickly add 200.0

......