The configuration method of standard buffer solution commonly used in pH meter:
Three commonly used standard buffer solutions:
Potassium hydrogen phthalate (KHC8H4O4), ph value is 4.00;
Mixed phosphate (Na2HPO4): mixed salt solution of potassium dihydrogen phosphate and disodium hydrogen phosphate, pH 6.86;
Borax (Na2B4O7 10H2O) solution, ph value is 9.18;
1. The preparation method of potassium hydrogen phthalate solution
Using a precision balance, weigh 10.12g of potassium hydrogen phthalate (KHC8H4O4) dried at 115±5 for 2-3 hours, add water to dissolve and dilute to 1000ml.
2. Preparation method of mixed phosphate solution
Using a precision balance, weigh 4.303 g of anhydrous disodium hydrogen phosphate and 1.179 g of potassium dihydrogen phosphate dried at 115±5 for 2-3 hours, add water to dissolve and dilute to 1000 ml.
Phosphate standard buffer preparation of pH=6.8:
Using a precision balance, weigh 3.533 g of anhydrous disodium hydrogen phosphate and 3.387 g of potassium dihydrogen phosphate dried at 115±5 for 2-3 hours, add water to dissolve and dilute to 1000 ml.
3. Preparation method of borax solution
Use a precision balance to weigh 3.80g of borax (note: avoid weathering), add water to dissolve and dilute to 1000ml, store it in a polyethylene plastic bottle, seal it well, and avoid contact with carbon dioxide in the air.
Note: The pH standard solution should be diluted in a smaller beaker to reduce the pH standard solution sticking to the wall of the beaker.
After the pH standard buffer is prepared, it should be sealed and stored in a dry place to avoid deliquescence and deterioration due to high air humidity. Alkaline standard solutions should be sealed in polyethylene bottles. Prevent carbon dioxide from forming carbonic acid after entering the standard solution, lowering its pH value.
