What is the pH of Hach buffers at different temperatures?

Document ID

Document ID TE2842

Version

Version 3.0

Status

Status Published

Published Date

Published Date 18/04/2019
Question
What is the pH of Hach buffers at different temperatures?
Summary
pH verses temperature Information.
Answer
The relationship of pH and temperature for a buffer is dependent on its formulation.

Buffer Solution, pH 4.01, Color-coded Red Product # 22834XX is a Phthalate buffer following SM 4500-H+ B.
Buffer Solution, pH 10.01, Color-coded Blue Product # 22836XX is a Bicarbonate-Carbonate buffer following SM 4500-H+ B.

Therefore, Standard pH values by temperature Table II in SM 4500-H+ B is true for these buffers.

In SM 4500-H+ B there is not a formulation for a buffer that would be pH 7.00 at 25 °C. There is a pH 6.86 and a pH 7.41 using a mixture of Disodium Hydrogen Phosphate and Potassium Dihydrogen Phosphate. Buffer Solution, pH 7.00, Color-coded Yellow Product # 22835XX is prepared with the same composition just at different ratios to give pH 7 at 25 °C. This formulation matches that of the Radiometer IUPAC Certified Buffer Standard Solution, pH 7.000 Product # S11M004. Attached is an example certificate of Conformance for the IUPAC pH 7 buffer that includes a table for pH vs Temperature that would also be true for the Hach Buffer Solution, pH 7.00, Color-coded Yellow Product # 22835XX since it uses the same formulation.
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