AWWA B402:2006 pdf download.Ferrous Sulfate
5.2.2.1 Moist or dried ferrous sulfate. Test samples of moist or dried ferrous sulfate shall be obtained from one of the three material samples. The dried ferrous sulfate sample shall be divided into two samples, one of 150–200 g for physical screen size determination and a second of approximately 100 g for the chemical analyses. The sample for physical screen size shall be used for the sieve analysis (Sec. 5.2.3). The sample for chemical analyses shall be reduced by either mechanical grinding or in a mortar by hand to such fineness that all of it passes through a No. 30 US Standard Sieve. These operations shall be carried out rapidly to minimize the change in moisture content of the sample. After thorough mixing, the sample for chemical analyses shall be stored in an airtight glass container.
5.2.2.2 Liquid ferrous sulfate. Test samples of liquid ferrous sulfate shall be obtained from the material sample and shaken thoroughly before each test portion is withdrawn for analysis.
5.2.3 Sieve analysis for dried ferrous sulfate. Transfer the 150–200 g sample (from Sec. 5.2.2.1) to an 8-in. diameter set of US Standard Sieves composed of a No. 4 sieve, a No. 10 sieve, and a pan. Sieve by lateral and vertical motions accompanied by jarring action. Continue 5 min or until an additional 3 min of sieving time fails to change the results of any sieve fraction by 0.5 percent of total sample weight.
2. Stannous chloride reduction method: To the solution, add 10 mL of hydrochloric acid and heat to boiling. Add the stannous chloride solution by drops until the last trace of greenish-yellow color disappears. Then add one additional drop in excess to ensure complete reduction. Cool to 20 o C, add 60 mL of deionized water, and then add, in one pouring, 20 mL of saturated mercuric chloride solution with agitation to ensure instantaneous mixing. If a white, milky precipitate forms, add 30 mL of 25 percent phosphoric acid solution and 7 to 10 drops of diphenylamine barium sulfonate indicator. The volume of the solution should be between 150 and 200 mL. If a dark precipitate forms, there is too much stannous chloride. If no precipitate forms, there is too little stannous chloride. In either case, the entire procedure must be repeated on a new sample.
3. Titration: Slowly titrate the prepared solution with standard potassium dichromate solution, stirring constantly. Near the end point, the green color of the solution deepens to a blue green or, in the presence of large amounts of iron, to grayish blue. Beyond this point, the dichromate solution is added by drops until the color changes to an intense violet blue. Subtract an indicator correction of 0.05 mL from the volume of dichromate used.AWWA B402 pdf download.