EPA Method 130.2

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EPA Method 130.2:
Total Hardness of Water by Titrimetry. Official Name: Hardness, Total (mg/L as CaCO3)(Titrimetric, EDTA)

Eriochrome Black T (EBT) indicator is added to the sample, and EDTA (ethylenediamine tetraacetate) is titrated into the sample. EBT has a red color in the presence of free calcium and magnesium ions. As EDTA is added to the sample it complexes (sequesters) the ions. In the absence of free calcium and magnesium the EBT will turn blue indicating the endpoint of titration.

This method determines total hardness in drinking, surface, and saline waters; and domestic and industrial wastes.

Methods for the Chemical Analysis of Water and Wastes (MCAWW) (EPA/600/4-79/020)

(1) A number of metal ions may cause fading or indistinct end points (Standard Methods 2340C provides a listing of interfering metals and their potential effects). (2) Suspended or colloidal organic matter can interfere with the endpoint.

QC Requirements:
not included

Maximum Holding Time:
6 months



Method is suitable for all concentration levels.

Precision and accuracy values were calculated using interlaboratory data from EPA-managed Water Pollution (WP) performance evaluation studies.

DL is taken as lowest point of the effective range.

Revision Number:
Issued 1971; Editorial Revision 1978 and 1982

Test Description:
Hardness, Total - Ti

Instrument used for this test: