SEDL / STP / STP823-EB / STP31877S

Simulated Precipitation Reference Materials: Measurement of pH and Acidity

Koch, WF
Research chemist, Center for Analytical Chemistry, National Bureau of Standards, Washington, D.C.

Marinenko, G
Research chemist, Center for Analytical Chemistry, National Bureau of Standards, Washington, D.C.

Pages: 8    Published: Jan 1983

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Abstract

The Center for Analytical Chemistry of the National Bureau of Standards has prepared and analyzed several series of simulated precipitation reference materials to be used as a means of intercalibrating atmospheric monitoring stations. In addition, research has shown serious errors in the measurement of pH and acidity determined in solutions of low-acidity and low-ionic strength. Contingent on further research pH measurements of acid rain should not be reported with greater confidence than 0.1 pH number. Titrations for total acidity should be performed to an inflection point or Gran plot endpoint and not to a fixed pH endpoint. Improved measurement protocols and reference standards are necessary to assure measurement comparability and consistency throughout the nation.