pH measurement is a relative measurement. It only indicates the difference in pH between a standard solution and an unknown solution. In actual measurement, a standard buffer solution needs to be regularly calibrated. Therefore, in order to achieve the same value, a pH scale must be established. The pH scale range is set at 0-14pH, and the value of the pH scale is determined by the pHs value of the reference buffer solution.
Therefore, the meaning of the pH scale can be expressed as: According to the definition of pH, select several pH buffer solutions in the range of 0 to 14 pH as the fixed points of the pH scale, and use the most accurate method that can be achieved by contemporary technology to determine their pHs. value. There are two kinds of pH scales in the world, namely multiple reference pH scales and a single reference pH scale. China uses multiple reference pHs scales.
pH buffer solution
The pH buffer solution is a solution that can keep the pH value stable. If a small amount of acid or alkali is added to this solution, or a small amount of acid or alkali is generated by a chemical reaction in the solution, and the solution is appropriately diluted, the pH value of the solution is basically stable, which can resist small amounts of acid Or alkali or dilution, and make the pH value difficult to change the solution is called pH buffer solution.
The pH standard buffer solution has the following characteristics:
⑴ The pH value of the standard solution is known and reaches the specified accuracy.
⑵The pH value of the standard solution has good reproducibility and stability, with a larger buffer capacity, a smaller dilution value and a smaller temperature coefficient.
⑶ The preparation method of the solution is simple.
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