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Chemistry LibreTexts

Experimental Details

Water samples were collected both upstream and downstream of the dam. Water quality measurements required the following materials. 1) A low-cost estuary and marine test kit from LaMotte was used to test for phosphate ( A phosphorus test tab was added to 10 ml of water sample. The test tab contains ammonium molybdate which reacts with orthophosphate to produce a phosphomolybdate complex. This complex when reduced by stannous chloride or ascorbic acid produces a blue color. A phosphate color chart was used to match the color obtained with the sample to record its phosphate content ( An Enviro-Safe Pocket Thermometer from Sigma-Aldrich was used to record the temperature. 2) The pH of the samples was measured using a pHep sensor by Hanna (Model No. HI 98107). The pH probe was calibrated using standard pH buffers 4, 7 and 10 before actual measurement. Once calibrated, the instrument could be used to measure pH. 3) The total carbonate was determined in the lab by titrating a 50 ml sample with 0.02 N sulfuric acid to pH 4.3. The titration was followed by using phenolphthalein indicator until pH 8.3 and methyl orange indicator until pH 4.3. 4) The calcium hardness was measured using a Hach total calcium and magnesium hardness water kit (Model HA-4P-MG-L). The hardness was essentially from calcium and magnesium bicarbonates. It was found by titration using EDTA. The hardness in mg/L was reported as equivalent of calcium carbonate. The detailed procedure for testing calcium hardness is available at the Hach website 5) The dissolved oxygen was also measured using a Hach dissolved oxygen (DO) kit (Model OX-2P) which uses a modified Winkler method. The stepwise procedure for finding dissolved oxygen is available at the Hach website

No chemicals or procedures used by students present any significant hazards; however, nothing should be ingested. Protective garments and gloves should be worn at all times. Hands should be washed after all sampling. Also, students should be warned against drinking their samples at ANY time before, during, or after collection and testing.