TM 5-6630-215-12b.Iron,Ferrous (Fe++) Test - 1,10-Phenanthroline Method (figs.2-11 and 2-12, and para 2-18).(1) Iron in Water.Natural water contain variable but minoramounts or iron.Iron in ground waters is normally present in theferrous (Fe++) state which is easily oxidized to ferric (Fe+++) onexposure to air.Iron can enter a water system by leaching naturaldeposits from iron-bearing industrial wastes, effluents from picklingoperations,or acidic mine drainage.(a) Iron in domestic water supply systems stains laundry andprocelain,causing more of a nuisance than a potential health hazard.Taste thresholds of iron in water are 0.1 mg/1 ferrous iron and 0.2mg/l ferric iron, giving a bitter or astrigent taste.Water used inindustrial processes usually contain less than 0.2 mg/l total iron.Domestic water supplies containing more than 0.3 mg/l total iron areobjectionable due to staining and taste considerations.(b) The Iron, Ferrous, (Fe++) test 1, 10-Phenanthroline Methodis the most well-known test for ferrous and total iron. The 1, 10-phenanthroline reagent gives an orange color with ferrous iron and isfree from common interferences.The indicator is combined with areducing agent for total iron analysis in a single powder formulation.The amount of ferric iron present can be determined as the differencebetweem the amount of ferrous iron and the results of a total irontest paragraph 2-19.c.The Iron reagent converts all iron present inthe sample to the ferrous state,including precipitated or suspendediron such as rust, where it reacts with the 1, 10-phenanthroline togive the orange color necessary for the determination.(2) Ferrous Iron (Fe++) Test Procedure.NOTESamples should be analyzed as soon as possibleafter collection to prevent air oxidation offerrous iron (Fe++) to ferric iron (Fe+++).Iron reagent powder pillows are stable up to 24months depending on storage and handling conditions.A cool, dry atmosphere is recommended for longestshelf life.The iron reagent powder can bechecked by adding the contents of one pillow toabout 25 ml of water containing visual rust. Ifthe characteristic orange color does not develop,then the reagent has deteriorated beyond use andshould be discarded and reordered.A large excess of iron will inhibit full colordevelopment.A diluted sample should be testedif there is any doubt about the validity of aresult.To extend the range of the test, asample dilution is necessary (para 2-10a, table2-1).Change 12-43
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business
