Application Note

Iron For Water And Seawater

Source: Hach

Natural waters contain variable, but minor, amounts of iron, despite its universal distribution and abundance. Iron in ground waters is normally present in the ferrous (Fe2+), or soluble state, which oxidizes easily to ferric (Fe3+) iron on exposure to air. Iron can enter a water system from leaching of natural deposits, iron-bearing industrial wastes, effluents of pickling operations, or from acidic mine drainage.

Iron in domestic water supply systems stains laundry and porcelain, causing more of a nuisance than a potential health hazard. Taste thresholds of iron in water, 0.1 mg/L for Fe2+ and 0.2 mg/L for Fe3+, result in a bitter or astringent taste. Water used in industrial processes must contain less than 0.2 mg/L of total iron.

Three methods of colorimetric iron analysis are used in Hach procedures. The 1,10- Phenanthroline Method is the best-known test for iron. The Fe2+ procedure uses Ferrous Iron Reagent Powder containing 1,10-Phenanthroline as an indicator. Total iron determination or analysis uses FerroVer Iron Reagent. FerroVer Iron Reagent contains 1,10-Phenanthroline, combined with a reducing agent, to convert all but the most resistant forms of iron present in the sample to Fe2+.