Argentimetric Method: ASTM D 512-89, Chloride Ion in Water, Test Method B. APHA Standard Methods, 19th ed., p. 4-49, Method 4500-Cl- B (1995).
Chloride is the most common inorganic anion found in water and wastewater. Salt (sodium chloride)passes through the human digestive system unchanged to become the principal source of chlorides in raw sewage. A limit of 250 mg/L Cl has been placed on drinking water supplies, as this is the level at which water begins to taste salty when sodium is the cation. When calcium or magnesium is the cation, up to 1000 mg/L Cl can be tolerated with no salty taste. Natural sources of salt are the ocean and various salt deposits above and below ground.
Chloride is very corrosive to most metals in systems with elevated pressures and temperatures such as boilers and oil drilling equipment. In coastal areas, higher than normal chloride concentrations in drinking water can indicate seepage of seawater into the water supply or the presence of industrial effluents.
The Titrimetric Methods. (1) Mercuric Nitrate Method. Mercuric nitrate titrant in acid solution with diphenylcarbazone as the end point indicator. Bromide and iodide will titrate as chloride. Results are expressed as ppm (mg/L) Cl. Shelf-life: Although the reagent itself is stable, the diphenylcarbazone, used as the end point indicator, has a limited shelf-life. We recommend stocking chloride test kits in quantities that will be used within 4 months. Replacement diphenylcarbazone Titret tips have a 6-month shelf-life; the activator solution has a 4-month shelf-life. (2) Silver Nitrate Method. Silver nitrate titrant with potassium dichromate as the end point indicator. Bromide and iodide will titrate as chloride. Results are expressed as ppm (mg/L) Cl. Shelf-life: Two years.
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