TM 5-6630-215-12In domestic water systems, sulfates do not appear to cause anyincreased corrosion on brass fittings but concentrations above 200 mg/ldo increase the amount of lead dissolved from lead pipes.(b) The procedure for determining sulfate is a modification ofthe Barium Sulfate Turbidimetric Method.A single, dry powder reagentcalled sulfate reagent will cause a milky precipitate to form ifsulfate is present.The sulfate reagent also contains a stabilizingagent to hold the precipitate in suspension for turbidimetric analy-sis.Theamount of(2)amount of turbidity formed is directly proportional to thesulfate resent.Sulfate Test Procedure.NOTEFiltering (para 2-22j) is recommended for highlycolored and/or turbid water samples.Large amountof color or turbidity will interfere and causehigh readings.The filtered water is then usedin steps (a) and (c).The results will not be affected if the reagentpowder does not completely dissolve.After each test the sample cells should becleaned with soap and a brush.A white film willdeposit on the inside of the cells and lead toerrors in future determinations if this is notdone soon after each test.Silica in excess of 500 mg/l will interfere.To extend the range of the test, a sample dilutionis necessary (para 2-10a and table 2-1).(a) Fill a clean graduated cylinder to the 25 ml mark, thenpour into a sample cell.(b) Add the contents of one sulfate reagent powder pil-low and swirl to mix.A white turbidity will develop if sulfateis present.Allow the sample to stand 5 minutes but not more than 10minutes before step (c) and (d).(c) Fill another sample cell to the 25 ml mark with originalwater sample and place it in the cell holder.Insert the sulfatemeter scale into the meter and adjust the wavelength dial to 450 nm.Adjust the light control for a meter reading of zero mg/l.(d) Replace the blank sample (step (c)) with the prepared sam-ple in the cell holder and read the mg/l (SO4).2-50
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