ASTM D512-89 pdf free.Standard Test Methods for Chloride Ion In Water.
Though not specified in the research report, the preci-sion statement is presumed to have been obtained using Type IIreagent water. It is the responsibility of the analyst to assure thevalidity of this test method for untested matrices.
This test method was validated for the concentrationrange 8.0 to 250 mg/L Cl7.
Dilute mercuric nitrate solution is added to an acidifiedsample in the presence of mixed diphenylcarbazone-bromophenol blue indicator. The end point of the titration is theformation of the blueviolet mercury diphenylcarbazone complex.
The anions and cations generally found in water offer nointerference.Zinc, lead, nickel, and ferrous and chromous ionsaffect solution and endpoint colors， but do not reduce theaccuracy of the titration when present in concentrations up to100 mg/L.Copper is tolerable up to 50 mg/L.Titration in thepresence of chromate ion requires indicator with extra back-ground color (alphazurine) and prior reduction for concentrations above 100 mg/L. Ferric ion above 10 mg/L must bereduced before titration，and sulfite ion must be oxidized.Bromide and fluoride will be partially titrated with the chlo-ride. Quaternary ammonium salts also interfere if present insignificant amounts (1 to 2 mg/L). Deep color may alsointerfere.
If chromate ion is present in the absence of iron and inconcentration less than 100 mg/L, use the alphazurine modifiedmixed indicator (Note 1) and acidify the sample as described in12.2 but to pH 3 as indicated by pH indicating paper.Titrate thesolution as described in 12.3, but to an olive-purple end point.12.5 If chromate ion is present in the absence of iron and inconcentration greater than 100 mg/L,add 2 mL of freshhydroquinone solution and proceed as described in 12.2 and12.3. If ferric ion is present in the absence or presence ofchromate ions, use a sample of such volume as to contain nomore than 2.5 mg of ferric ion or of ferric ion plus chromateion.Add 2 mL of fresh hydroquinone solution, and proceed asdescribed in 12.2 and 12.3.