EPA Method 305.1:
Acidity by Titration. Official Name: Acidity (Titrimetric)
The pH of the sample is determined and a measured amount of standard acid is added, as needed, to lower the pH to 4 or less. Hydrogen peroxide is added, the solution boiled for several minutes, cooled, and titrated electrometrically with standard alkali to pH 8.2.
This method is applicable to surface waters, sewages and industrial wastes, particularly mine drainage and receiving streams, and other waters containing ferrous iron or other polyvalent cations in a reduced state.
Methods for the Chemical Analysis of Water and Wastes (MCAWW) (EPA/600/4-79/020)
Suspended matter present in the sample, or precipitates formed during the titration may cause a sluggish electrode response. This may be offset by allowing a 15-20 second pause between additions of titrant or by slow dropwise addition of titrant as the endpoint pH is approached.
Maximum Holding Time:
Approximately 10 mg/L acidity to approximately 1000 mg/L as CaCO3, using a 50 mL sample.
A multilaboratory study conducted by ASTM on 4 acid mine waters (with concentrations up to 2000 mg/L CaCO3) were used to determine precision.
Issued 1971; Technical Revision 1974
Instrument used for this test: