EPA Method 325.3

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EPA Method 325.3:
Chloride by Titrimetry. Official Name: Chloride (Titirmetric, Mercuric Nitrate)

An acidified sample is titrated with mercuric nitrate in the presence of mixed diphenylcarbazone-bromophenol blue indicator. The end point of the titration is the formation of blue-violet mercury diphenylcarbazone complex.

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

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

(A) Ions: Anions and cations at concentrations normally found in surface waters do not interfere.(B) Sulfite: Sulfite interference can be eliminated by oxidizing the 50 mL of sample with 0.5 to 1 mL of H202.

QC Requirements:

Maximum Holding Time:
28 days (MCAWW, Table 1).



The method is suitable for all concentration ranges of chloride; however, a sample aliquot containing no more than 10-20 mg/50 mL should be used.

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


Revision Number:
Issued 1971; Editorial Revision 1978 and 1982

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Examples:  8260

Examples:  Dioxin
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