TM 10-6630-245-13&PCAUTIONAfter recording the reading, immediately clean the sample cells with detergent and a brush. Awhite film will deposit on the inside of the cells which can lead to errors in future tests if this isnot done soon after each test.f.InterpretationofResults:NOTEResults as read from the meter scale are in mg/l of sulfate ion (SO4).If the results are near or at the maximum reading of 150 mg/l, the test should be performed again using a diluted sample.Use the graduated cylinder to measure exactly 12.5 ml of sample water and pour into the test cell. Then add 12.5 ml ofdeionized water to the same sample cell. Repeat the test using this water sample and multiply readings on the meterscale by 2.NOTEThe presence of silica in the water sample in excess of 500 mg/l will interfere.g.Refer to para 2.6.2 for shut down of the Spectrophotometer.2.6.8.18. TurbidityTest.a.PurposeofTest:To determine amount of suspended solids in a water sample.b.Range:0 to 500 FTUc.EquipmentUsed:Found in Main Carrying Case, para 1.8, fig. 1-1Spectrophotometer, (20), fig. 1-1Graduated cylinder, (31), fig. 1-1d.GeneralTechniquesUsed:Refer to paragraphs cited below as required by procedure.Planning the Test, para 2.6.1.1Cleaning Glassware, para 2.6.1.2Handling and Storing Reagents, para 2.6.1.3Collecting Water Samples, para 2.6.1.4Mixing, para 2.6.1.5Using Graduated Cylinders, para 2.6.1.6Spectrophotometer, para 2.6.2.2e.TestProcedure:WARNINGHigh voltage used with Spectrophotometer. Misuse can cause electrical shock and damageequipment. When operating with 115V or 220V power, make sure the power source andequipment are in ground potential. Ensure that the power cable connections are correct for thedesired voltage power before connecting the power source.(1)Refer to para 2.6.2 for setup and operation of the Spectrophotometer.(2)Fill one of the two spectrophotometer sample cells(7, fig. 2-5) with 25 ml of sample water. Use thegraduated cylinder(31, fig. 1-1) to collect and measure the water.(3)Fill the other sample cell with 25 ml of clear colorless water. Use the graduated cylinder(31) to measurethe amount. This will be the test blank. If filters are available, good enough results can usually beobtained by filtering some of the test sample. Then use the filtered water for the blank.2-54
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