Sulfate, Range: 0-150 mg/l, Turbidimetric Method

TM-5-6630-215-12 Alarm-Monitor Group (AMG) OA-9431/F88-9(V) CAGEC 97403 Manual
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TM 5-6630-215-12 NOTE The amount of indicator added is critical to the accuracy of the test and should be measured as carefully as possible. The strength of the indicator solution should be checked occasionally in the range normally being tested. Substitute: The indicator solution may be checked by running the test on a prepared buffer solution of a known PH. If the meter reading is too high the indicator has become too concentrated through evaporation of the solvent. If meter reading is too low, the indicator has deteriorated and should be replaced. (a) Take a water sample by accurately filling a clean grad- uated cylinder to the 25.0 ml mark. Pour the sample into a clean, dry sample cell. (b) Add exactly 1.0 ml of wide range pH indicator solution using the 1.0 ml transfer pipet and swirl to mix. (c) Fill another sample cell with about 25 ml of original water sample and place it into the cell holder. Insert the pH, wide range meter scale into the meter and adjust the wavelength dial to 520 nm. Adjust the light control so the meter needle rests at the far right end of the arc. (d) Replace the blank sample (step (c)) with the prepared sam- ple in the cell holder and read the pH value from the center or lower scale, according to the developed color. If the color does not correspond to those indicated on the center or lower scales, and/or the meter reading does not fall within the ranges indicated, proceed with step (e). (e) Adjust the wavelength dial to 615 nm and standardize the instrument as described in step (c). Place the prepared sample in the cell holder and read the pH value on the upper scale. g. Sulfate, Range: 0-150 mg/l, Turbidimetric Method (para 2-18 and figs. 2-11 and 2-12). (1) Sulfate appears in natural waters in a wide range of concen- trations. Mine waters and industrial effluents frequently contain large amounts of sulfate from pyrite oxidation and the use of sulfuric acid. (a) Public Health Service drinking water standards call for not more than 250 mg/l of sulfate because of its cathartic action. The taste threshold of magnesium sulfate is 400 to 600 mg/l and for calcium sulfate is 250 to 800 mg/l. Sulfate may be either beneficial or detrimental in water used for manufacturing and domestic supply. 2-49

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