NEMI Method Summary


Method Summary Information

Method Number:

973.52B

Media:

WATER

Revision:

15th Edition (1990)

Method Source:

AOAC International

Subcategory:

INORGANIC

Analytes in this method

Official Name:

Hardness of Water by EDTA Titrimetric Method

Descriptive Name

Hardness of Water

Source Info:

AOAC International
481 North Frederick Avenue
Suite 500
Gaithersburg, Maryland 20877-2417 USA
Phone: 1-301-924-7077 (worldwide), or 1-800-379-2622 (toll-free from North America)
Fax: 1-301-924-7089
E-mail: aoac@aoac.org

Citation:

AOAC Methods Volume 1, 16th Ed. (1998)

Brief Method
Summary:

Ca and Mg at pH 10 in presence of dye eriochrome black T are wine red. When completely complexed with EDTA, solution becomes blue. Mg must be present for satisfactory end point and is added as MgEDTA. End point sharpness increases with pH, but high pH may cause precipitation of Ca(OH)2 or Mg(OH)2 and cause color changes of dye. pH of 10.0 +/- 0.1 is satisfactory compromise. Limit of 5 min for titration minimizes precipitation. Heavy metal interference is minimized by complexing with cyanide.

Scope And
Application:

Applicable to drinking water, surface water, and domestic and industrial wastewaters.

Applicable
Conc Range:

None given.

Interferences:

Not specified in method.

QC Requirements:

Not Included

Sample Handling:

No information given.

Max Holding Time:

Relative Cost:

Less than $50

URL to obtain ordering information for this method:

http://www.aoac.org/pubs/oma.htm

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Method Summary Information