GB/T 23595.5-2009Test methods of rare earth yellow phosphor for white LED lamps - Part 5: Determination of pH value (English PDF)

3.1 pH meter

with temperature compensation function, range 0 to 14, and the accuracy of ± 0.1.

3.2 Standard solution

pH values were 4.00,6.86,9.18.

3.3

potassium chloride solution (0.1mol/L). Weigh 3.728g potassium chloride (AR grade) in 100mL beaker, adding an appropriate amount of deionized water and dissolved

After the solution transferred to 500mL volumetric flask, and diluted with water to volume, and mix.

3.4 magnetic stirrer

power <=90W, adjustable speed timing.

3.5 Magnetic sub

about 25mm.

3.6 plastic beaker

50mL.

3.7 Analytical Balance

Precision 0.001g.

3.8 Pipette

20mL.

3.9 Deionized water

Conductivity <=2µS/cm.

4.1 Production Solution

4.1.1

Using an analytical balance (3.7) weigh the sample into 2g 50mL plastic beakers (3.6), and with a pipette (3.8) was added

20mL of deionized water (3.9), into a 25mm long magnetic sub (3.5), cover the slides.

4.1.2

The beaker containing the sample and water on a magnetic stirrer (3.4), the mixture was stirred after 20min standing stratification.

4.1.3

medium speed filter paper filtered upper clear liquid, and add about 0.05mL potassium chloride solution (3.3) in the supernatant liquid, with a glass rod to be

Measuring liquid, stir.

4.2 Test

4.2.1

Adjust the "Temperature Compensation" knob to the temperature at this time of the test solution, and then switch to the "pH" place.

4.2.2

The electrode into standard solution pH = 6.86 (3.2), shake the bottle to be balanced, adjust the "positioning" knob until the instrument displays the phase

The corresponding values.

4.2.3

Place the electrode in pH = 4.00 or pH = 9.18 of the standard solution (3.2), shake the bottle, to be balanced, adjust the "slope" knob

Until the instrument displays the corresponding pH. Repeating the above steps at least three times, until the respective two pH values stable. After calibration is complete,

"Positioning", "Slope" knob may not move again.

4.2.4

Place the electrode in the test solution, shake the bottle, to be balanced, the pH of the solution can be read from the instrument display.