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    222331
  • 1 This experiment was designed by John J. Dolhun and includes contributions from course textbooks, current literature, and others affiliated with 5.310 Updated by John Dolhun May 2017.

    2 MIT across the Charles River. Photograph by Anshul Nigham, on flickr. license BY-NC-SA.

    3 Charles River Watershed Association see http://www.crwa.org/watershed.html

    4 A Beginner’s Guide to Water Management, University of Florida, Florida Lakewatch, Department of Fisheries & Aquatic Sciences, 1st ed., June, 2004, p. 5.

    5 Dissolved Oxygen, Water Quality with Vernier, Computer 5, Vernier Software & Technology, Beaverton, OR, p. 1. 

    6 Various Material Safety Data Sheets: Malinckrodt Chemicals, J. T. Baker, Phillipsburg, NJ; Fischer Scientific, MSDS, Pittsburgh, PA

    7 Equations for reactions in this section adopted & modified from: John H. Nelson & Kenneth C. Kemp, Laboratory Experiments, Analysis of Water for Dissolved Oxygen, Chemistry the Central Science, 7th. Edition, Prentice Hall, 1997, p. 386. 

    8 Standard Methods for Examination of Water & Wastewater, 21st Ed., 2005, American Public Health Association & American Water Works Association, pp. 4-138 to 4-140. 

    9 Alsterberg, G., Methods for the determination of elementary Oxygen dissolved in water in the presence of nitrite, Biochem. Z., 159 (1925) 36. 

    10 L. W. Winkler, Berlin. Deut. Chem. Ges., 21 (1888) 2843.

    11 C. Numako and I. Nakai, Physica B, 208/209 (1995) 387-388.

    12 Adapted from: Standard Methods for Examination of Water & Wastewater, 21st Ed., 2005, American Public Health Association & American Water Works Association, pp. 4- 138 to 4-140.

    13 Many textbooks recommend boiling the water beforehand to remove dissolved CO2

    14 It is always important to mix a standard solution very thoroughly and it is surprising how much mixing is necessary. Unless this is done, significant differences in concentration can persist and cause lack of agreement in subsequent titrations. In the present instance, the sodium thiosulfate solution needs to be dispersed throughout the solution by repeatedly inverting the bottle and shaking vigorously. This procedure should be repeated every time you prepare to take out additional sodium thiosulfate.

    15 Adapted from: Standard Methods for Examination of Water & Wastewater, 21st Ed., 2005, American Public Health Association & American Water Works Association, pp. 4- 138 to 4-140.

    16 Solid potassium bi-iodate is available in high purity and is of a high enough molecular weight making it an excellent candidate as a primary standard for alkalimetry where starch is used as an indicator. The purpose of the drying period is to remove superficial moisture.

    17 Dissolve the KH(IO3)2 sample by swirling in 50 mL of warm water. Warming may be necessary as it is essential that the sample dissolve completely. Even a few small particles remaining can cause a serious titration error.

    18 Nichols, Ind. Eng. Chem., Anal. Ed., 1 (1929) 215.

    19 Possible source of error in the titration would be the air oxidation of I- to I2. If the solution is allowed to stand too long before it is titrated, the oxidation will produce values that may be too high.

    20 The starch solution must be added just before the endpoint is reached, that is at the point when the deep yellow color of the iodine solution turns to pale yellow or light amber. If the starch solution was added earlier the dark blue-black starch-iodide complex that forms would make it difficult to find the endpoint as the color change comes almost instantaneously so it is easier to watch for the approach of the endpoint with the yellow solution changing to a pale yellow color and then adding the aqueous starch solution.

    21 The starch endpoint is taken as the first distinct change from blue to colorless that persists for 10 seconds or more after thorough mixing. The color may not be permanent but may change back to blue in a matter of minutes or less. This should be disregarded and the endpoint should be taken as the first point at which the blue starch-iodide complex disappears resulting in a colorless solution. The student should think of some reasons for the possible return of the blue color and perhaps substantiate the reasoning with some chemical equations.

    22 Adapted from: Standard Methods for Examination of Water & Wastewater, 21st Ed., 2005, American Public Health Association & American Water Works Association, pp. 4- 138 to 4-140.

    23 Collection protocol adapted from: Joy Michaud, A Citizens Guide to Understanding & Monitoring Lakes and Streams (1994) Washington State Department of Ecology, 45-51.

    24 Poor SLDO % numbers could indicate a high period of decomposition with bacteria using up the available DO or could occur during a period of higher temperatures.

    25 Dissolved Oxygen, Water Quality With Calculators, Texas Instruments, 2006, p. 2.

    26 Lower supersaturated levels are probably not of major concern as water can go in and out of a supersaturated level of DO over short periods of time. However, any prolonged supersaturated levels of DO should be cause for concern as it can have the effect of forming gas bubbles in the body cavities of fish. The bubbles can block the blood flow to cells causing cell death.

    27 Dissolved Oxygen, Water Quality With Calculators, Texas Instruments, 2006, p. 2.

    28 W. D. Hatfield, A Nomograph for Dissolved Oxygen Saturation in Water, Sewage Works Journal, Vol. 13, No. 3 (May, 1941), pp. 557-560.

    29 Standard Methods for the Examination of Water and Wastewater, 12th ed., American Public Health Association, 1965, pp. 408-410.

    30 The background discussion on pH including ranges was adapted from: Joy Michaud, A Citizens Guide to Understanding & Monitoring Lakes and Streams (1994) Washington State Department of Ecology, p. 32.

    31 Background information adapted from the following however, the vanadomolybdate method used in this lab is not suitable for concentrations normally found in river water. The method used in this lab appears suitable for calculating the total phosphorous levels for something like raw sewage where the concentrations of phosphorous are high but not river water or fresh water lakes which require a more sensitive method: John H. Nelson & Kenneth C. Kemp, Chemistry the Central Science, Seventh Edition, Prentice Hall, (1997), pp. 377 to 383.

    32 Seth Jaffe, EPA Issues Construction Stormwater Rule—First National Standards with Numeric Limits, Law & The Environment, Published by Foley Hoag LLP, 2009.

    33 Strickland, J.D.H., and Parsons, T.R. (1968). Determination of Reactive Phosphorous. A Practical Handbook of Seawater Analysis, Fisheries Research Board of Canada, 167, 49-56.

    34 Solutions for the color-developing reagent were modified and adapted from the following: Strickland, J.D.H., and Parsons, T.R. (1968). Determination of Reactive Phosphorous. A Practical Handbook of Seawater Analysis, Fisheries Research Board of Canada, 167, 49-56; MIT Open Courseware, Earth, Atmospheric & Planetary Sciences, 12.097 Chemical Investigations of Boston Harbor, Lab 3: Determination of Phosphate, January (IAP) 2006.; Standard Methods for the Examination of Water and Wastewater, 20th ed. American Public Health Association, American Waterworks Association, Water Environment Federation, 4500-P Phosphorous and 4500-P E, Ascorbic Acid Method.

    35 Ascorbic acid is aerobically oxidized in air reacting with the oxygen in solution and therefore should only be prepared and used at the time of the lab.

    36 Procedure for cleaning collection bottles and glassware has been modified slightly and adapted from: MIT Open Courseware, Earth, Atmospheric & Planetary Sciences, 12.097 Chemical Investigations of Boston Harbor, Lab 3: Determination of Phosphate, January (IAP) 2006.

    37 The chloroform will appear as a bubble at the bottom of the bottle. It does not mix with the aqueous solution and is a toxin that keeps mold and bacteria from growing in the standard solution. It slowly evaporates over time and can be replenished if the bubble is no longer visible. The solution is stable for about four months. This has been adapted from: MIT Open Courseware, Earth, Atmospheric & Planetary Sciences, 12.097 Chemical Investigations of Boston Harbor, Lab 3: Determination of Phosphate, January (IAP) 2006.

    38 Volumes were modified however, the order of addition and quantitation was adapted from: MIT Open Courseware, Earth, Atmospheric & Planetary Sciences, 12.097 Chemical Investigations of Boston Harbor, Lab 3: Determination of Phosphate, January (IAP) 2006.

    39 Written by John J. Dolhun

    40 Source: Derived from “Standard Methods for Examination of Water and Wastewater” and verified with Department of Fisheries and Aquatic Sciences, Institute of Food and Agricultural Sciences, A Beginner’s Guide to Water Management—Oxygen and Temperature, University of Florida, Gainesville, Florida.

    41 After finding your measured value of DO in mg / L from the Charles River sample you can apply a correction factor to your measurement. Simply take your measured value and multiply it by the correction factor closest to the barometric pressure. This then becomes your corrected DO concentration.

    42 Once you have found your Pressure corrected DO concentration simply mark it on the bottom scale, then mark the corresponding temperature of the water on the upper scale. Use a ruler to connect the two points with a straight line. Read off your % saturation of DO at the intersection of your line on the middle scale.

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