pH meter (acidity meter) calibration method
The acidity meter should be regularly calibrated and calibrated to ensure that its precision and accuracy meet the requirements. How to calibrate a pH meter, or in other words, how to calibrate an acidity meter. There are two types of calibration methods: direct calibration using pre configured standard buffer, and self configuration of standard buffer before calibration. Let's take a look at these two different prerequisites and the same calibration method steps.
Tools and raw materials used for calibrating pH meters
(1) Standard buffer solution (should choose a standard buffer solution with a pH value close to the test solution), currently there are 7 types of standard solutions, and in China, the following 3 solutions are generally used: (when the pH value is at 25 ℃)
1. Potassium hydrogen phthalate (KHC8H4O4) pH 4.003; 0.05M
2. Mixed phosphate (Na2HPO4): a mixed salt solution of potassium dihydrogen phosphate and disodium hydrogen phosphate with a pH of 6.864; 0.025M
3. Borax (Na2B4O7 · l0H2O) pH 9.182; 0.01M
(2) The configuration methods of the three standard buffer solutions are as follows
1 pH4, Potassium hydrogen phthalate standard buffer solution:
Accurately weigh 0.12g of potassium hydrogen phthalate [KHC8H4O4] dried at 115 ± 5 ℃ for 2-3 hours, dissolve and dilute to 1000ml with water.
2 pH7, Phosphate standard buffer solution (pH 7.4):
Accurately weigh 4.303g of anhydrous disodium hydrogen phosphate and 1.179g of potassium dihydrogen phosphate dried at 115 ± 5 ℃ for 2-3 hours, dissolve and dilute to 1000ml with water.
Additional information: Precisely weigh 3.533g of anhydrous disodium hydrogen phosphate and 3.387g of potassium dihydrogen phosphate dried at 115 ± 5 ℃ for 2-3 hours using phosphate standard buffer solution (pH 6.8), dissolve and dilute to 1000ml with water.
3 pH9, Borax standard buffer solution:
Accurately weigh 3.80g of borax [Na2B4O7 · 10H2O] (note: avoid weathering), add water to dissolve and dilute to 1000ml, place in a polyethylene plastic bottle, seal tightly, and avoid contact with carbon dioxide in the air.
