...Topic : Determination of the amount of dissolved oxygen in a water sample by iodometry-the winkler’s method. Objective: To determine the amount of dissolved oxygen in a water sample by iodometry- the winkler’s method. Apparatus: volumetric pipette, 3 conical flask, burette, burette clamp, Pasteur pipette, reagent bottle, conical flask stopper, retord stand, white tile Materials: 2 ml manganese sulphate solution, 2 ml alkaline-iodine solution, 0.025M sodium thiosulphate solution, 2ml concentration sulphuric acid, starch solution Procedure 1. When sampling water, care must be taken to ensure that a good representative sample of the water to be analyzed is obtained. For most purposes, this includes attention to dissolved gases. Therefore, the water sample should be taken in a clean bottle which must be filled to overflowing and tightly sealed with stopper without introduction of air. If the water is sampled from a tap, it must be allowed to run for at least 5 minutes prior to sampling. For this purpose, you may collect the water into a 1 L reagent bottle fitted with a stopper. 2. The stopper is removed carefully from the conical flask and 2 mL of the manganese sulfate solution is added, discharging the reagent from the tip of a pipette put well below the water surface. Stopper is replaced. 3. Similarly, 2 mL of the alkaline-iodide solution is introduced. 4. The stopper is placed in the bottle, be sure that no air becomes entrapped. Some overflow may occur....
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...EXPERIMENT 11: DETERMINATION OF DISSOLVED OXYGEN IN A WATER SAMPLE (WINKLER METHOD) INTRODUCTION In an alkaline solution, dissolved oxygen will oxidize manganese(II) to the trivalent state. 8OH-(aq) + 4Mn2+(aq) + 2H2O(l) －－＞ 4Mn(OH)3(s) The analysis is completed by titrating the iodine produced from potassium iodide by manganese(III) hydroxide. 2Mn(OH)3(s) + 2I-(aq) + 6 H+(aq) －－＞ 2Mn2+(aq) + I2(aq) + 6H2O(l) Sodium thiosulphate is used as the titrant. Success of the method is critically dependent upon the manner in which the sample is manipulated. At all stages, every method must be made to assure that oxygen is neither introduced to nor lost from the sample. Furthermore, the sample must be free of any solutes that will oxidize iodide or reduce iodine. Chemicals: Manganese(II) sulphate solution – prepared by dissolving 48 g of MnSO4.4H2O in water to five 100 cm3 solution; alkaline potassium iodide solution—prepared by dissolving 15 g of KI in about 25 cm3 of water, adding 66 cm3 of 50% NaOH, and diluting to 100 cm3; concentrated sulphuriv(VI) acid; 0.0125 M sodium thiosulphate solution; starch solution (freshly prepared). Apparatus: 250 cm3 volumetric flask, 250 cm3 conical flask, measuring cylinders, titration apparatus, magnetic stirrer Procedure: 1. Use a 250 cm3 volumetric flask to collect water sample. Fill the flask completely with water without trapping any air bubbles. 2. Add 1 cm3 of manganese(II) sulphate solution to the sample using a pipette...
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...CONTENTS Dissolved Oxygen Measurement Page Section 1: Dissolved Oxygen (DO) Introduction 2 Section 2: Glossary 2 Section 3: Approved Methods 3 Section 4: Safety and Hygiene 3-4 Section 5: Sampling 4-5 Section 6: Effects of Temperature on DO 5 Section 7: Interpretations 5 Quiz 4.1 6 Section 8: Modified Winkler Method 6-9 Quiz 4.2 9 Section 9: The Electrometric Meter Method 9-11 Quiz 4.3 12 Section 10: QA/QC 12 Answers to Quizzes 13-14 Appendix A: References Appendix B: Dissolved Oxygen Reagents Appendix C: Sample Bench Sheets Chapter 4 DISSOLVED OXYGEN MEASUREMENT Section 1 : DISSOLVED OXYGEN (DO) INTRODUCTION The DO determination measures the amount of dissolved (or free) oxygen present in water or wastewater. Aerobic bacteria and aquatic life such as fish must have DO to survive. Aerobic wastewater treatment processes use aerobic and facultative bacteria to break down the organic compounds found in wastewater into more stable products that will not harm the receiving waters. Wastewater treatment facilities such as lagoons or ponds, trickling filters and activated sludge plants depend on these aerobic bacteria to treat sewage. The same type of aerobic wastewater treatment process occurs naturally in streams and ponds if organic matter is present, turning these bodies of water into “aerobic wastewater treatment plants.” If sufficient oxygen is not naturally supplied through wind and turbulence to replace the depleted oxygen, the...
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...CONTENTS Dissolved Oxygen Measurement Page Section 1: Dissolved Oxygen (DO) Introduction 2 Section 2: Glossary 2 Section 3: Approved Methods 3 Section 4: Safety and Hygiene 3-4 Section 5: Sampling 4-5 Section 6: Effects of Temperature on DO 5 Section 7: Interpretations 5 Quiz 4.1 6 Section 8: Modified Winkler Method 6-9 Quiz 4.2 9 Section 9: The Electrometric Meter Method 9-11 Quiz 4.3 12 Section 10: QA/QC 12 Answers to Quizzes 13-14 Appendix A: References Appendix B: Dissolved Oxygen Reagents Appendix C: Sample Bench Sheets Chapter 4 DISSOLVED OXYGEN MEASUREMENT Section 1 : DISSOLVED OXYGEN (DO) INTRODUCTION The DO determination measures the amount of dissolved (or free) oxygen present in water or wastewater. Aerobic bacteria and aquatic life such as fish must have DO to survive. Aerobic wastewater treatment processes use aerobic and facultative bacteria to break down the organic compounds found in wastewater into more stable products that will not harm the receiving waters. Wastewater treatment facilities such as lagoons or ponds, trickling filters and activated sludge plants depend on these aerobic bacteria to treat sewage. The same type of aerobic wastewater treatment process occurs naturally in streams and ponds if organic matter is present, turning these bodies of water into “aerobic wastewater treatment plants.” If sufficient oxygen is not naturally supplied through wind and turbulence to replace the depleted oxygen, the...
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...Environmental Chemistry of Boston Harbor – IAP 2006 Lab 1: DETERMINATION OF DISSOLVED OXYGEN BY WINKLER TITRATION 1. Background Knowledge of the dissolved oxygen (O2) concentration in seawater is often necessary in environmental and marine science. It may be used by physical oceanographers to study water masses in the ocean. It provides the marine biologist with a means of measuring primary production - particularly in laboratory cultures. For the marine chemist, it provides a measure of the redox potential of the water column. The concentration of dissolved oxygen can be readily, and accurately, measured by the method originally developed by Winkler in 1888 (Ber. Deutsch Chem. Gos., 21, 2843). Dissolved oxygen can also be determined with precision using oxygen sensitive electrodes; such electrodes require frequent standardization with waters containing known concentrations of oxygen. They are particularly useful in polluted waters where oxygen concentrations may be quite high. In addition, their sensitivity can be exploited in environments with rapidly-changing oxygen concentrations. However, electrodes are less reliable when oxygen concentrations are very low. For these reasons, the Winkler titration is often employed for accurate determination of oxygen concentrations in aqueous samples. 2. Scope and field of application This procedure describes a method for the determination of dissolved oxygen in aqueous samples, expressed as mL O2 (L water) -1. The method...
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...Environmental Chemistry of Boston Harbor – IAP 2006 Lab 1: DETERMINATION OF DISSOLVED OXYGEN BY WINKLER TITRATION 1. Background Knowledge of the dissolved oxygen (O2) concentration in seawater is often necessary in environmental and marine science. It may be used by physical oceanographers to study water masses in the ocean. It provides the marine biologist with a means of measuring primary production - particularly in laboratory cultures. For the marine chemist, it provides a measure of the redox potential of the water column. The concentration of dissolved oxygen can be readily, and accurately, measured by the method originally developed by Winkler in 1888 (Ber. Deutsch Chem. Gos., 21, 2843). Dissolved oxygen can also be determined with precision using oxygen sensitive electrodes; such electrodes require frequent standardization with waters containing known concentrations of oxygen. They are particularly useful in polluted waters where oxygen concentrations may be quite high. In addition, their sensitivity can be exploited in environments with rapidly-changing oxygen concentrations. However, electrodes are less reliable when oxygen concentrations are very low. For these reasons, the Winkler titration is often employed for accurate determination of oxygen concentrations in aqueous samples. 2. Scope and field of application This procedure describes a method for the determination of dissolved oxygen in aqueous samples, expressed as mL O2 (L water) -1. The method...
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...EXPERIMENT 1 DETERMINATION OF DISSOLVED OXYGEN IN WATER INTRODUCTION The dissolved oxygen content is an important index when considering its suitability for town supply. A good clean potable water will give dissolved oxygen value close to the theoretical value for the saturated solution of oxygen in water. When there is pollution from organic matter and other trade effluents, the dissolved oxygen is up in various biochemical oxidation processes and its is only slowly replaced through surface absorption. Such water will give a low dissolved oxygen content until oxidation is completed. Adequate dissolved oxygen is necessary for the life of fish and other aquatic organisms. The methods described below for the determination of oxygen in water is based on that devised by Winkler. When manganese hydroxide is precipitated in the water sample it is quickly oxidized to higher hydrated oxides (probably in the four valent state) by the dissolve oxygen. Iodine, equivalent to the dissolved oxygen content, is then liberated on acidification in the presence of iodine, and it may be titrated with standard thio‐sulphate. INTERFERENCES AND PRE – TREATMENT Most oxidising and reducing substances e.g dissolved organic substances, nitrite ions, higher‐valency manganese compounds, active chlorine, sulphide and sulphite ions, iron (II) and irons interfere. The influence of the dissolved organic substances can be excluded by conversion of the manganese hydroxides...
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...Determination of Oxygen dissolved in water by Winkler’s Method History The test was first developed by Lajos Winkler while working on his doctoral dissertation in 1888. The amount of dissolved oxygen is a measure of the biological activity of the water masses. Phytoplankton and macroalgae present in the water mass produce oxygen by way of photosynthesis. Bacteria and eukaytotic organisms (zooplankton, algae, fish) consume this oxygen through respiration. The result of these two mechanisms determines the concentration of dissolved oxygen, which in turn indicates the production of biomass. The difference between the physical concentration of oxygen in the water (or the theoretical concentration if there were no living organisms) and the actual concentration of oxygen is called the biological demand in oxygen. Principle: The Winkler test is used to determine the level of dissolved oxygen in water samples and to estimate the biological activity in the water sample. An excess of Manganese(II) salt, iodide (I-) and hydroxide (OH-) ions are added to a water sample causing a white precipitate of Mn(OH)2 to form. This precipitate is then oxidized by the dissolved oxygen in the water sample into a brown Manganese precipitate. In the next step, a strong acid (either hydrochloric acid or sulphuric acid) is added to acidify the solution. The brown precipitates then convert the iodide ion (I-) to Iodine. The amount of dissolved oxygen is directly proportional to the titration of Iodine...
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...First devised in 1889, the Winkler method is considered the "gold standard" for measuring the concentration of dissolved oxygen in a sample of water. Through a series of chemical reactions, the O2combines with iodine to form a golden yellow chemical. Therefore each oxygen molecule is associated with an iodine molecule, and we can measure oxygen by measuring the iodine. When the iodine is neutralized by the addition of sodium thiosulfate, the golden color disappears , and we can determine how much iodine (hence oxygen) was in the sample. (Note: some oxygen test kits use a starch indicator that turns the iodine solution from yellow to a deep blue color to make it easier to distinguish the color change.) Once the water sample is collected, it is important to "fix" the sample immediately. Phytoplankton, bacteria, and other organisms in the sample can quickly change the oxygen content of the sample through photosynthesis and respiration. The first step of the Winkler method is the addition of manganous sulfate (a source of manganese ions) to the sample, quickly followed by the addition of lithium hydroxide (a strong base) and potassium iodide (a source of iodine). In the presence of the strong base, each oxygen atom binds with a manganese ion to form a manganous hydroxide complex. This reaction creates a pale precipitate that will eventually sink to the bottom of the sample container. Sulfuric or sulfamic acid is added to the solution to reduce the pH and dissolve the precipitate...
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...EXPERIMENT 11: DETERMINATION OF DISSOLVED OXYGEN IN A WATER SAMPLE (WINKLER METHOD) INTRODUCTION In an alkaline solution, dissolved oxygen will oxidize manganese(II) to the trivalent state. 8OH-(aq) + 4Mn2+(aq) + 2H2O(l) －－＞ 4Mn(OH)3(s) The analysis is completed by titrating the iodine produced from potassium iodide by manganese(III) hydroxide. 2Mn(OH)3(s) + 2I-(aq) + 6 H+(aq) －－＞ 2Mn2+(aq) + I2(aq) + 6H2O(l) Sodium thiosulphate is used as the titrant. Success of the method is critically dependent upon the manner in which the sample is manipulated. At all stages, every method must be made to assure that oxygen is neither introduced to nor lost from the sample. Furthermore, the sample must be free of any solutes that will oxidize iodide or reduce iodine. Chemicals: Manganese(II) sulphate solution – prepared by dissolving 48 g of MnSO4.4H2O in water to five 100 cm3 solution; alkaline potassium iodide solution—prepared by dissolving 15 g of KI in about 25 cm3 of water, adding 66 cm3 of 50% NaOH, and diluting to 100 cm3; concentrated sulphuriv(VI) acid; 0.0125 M sodium thiosulphate solution; starch solution (freshly prepared). Apparatus: 250 cm3 volumetric flask, 250 cm3 conical flask, measuring cylinders, titration apparatus, magnetic stirrer Procedure: 1. Use a 250 cm3 volumetric flask to collect water sample. Fill the flask completely with water without trapping any air bubbles. 2. Add 1 cm3 of manganese(II) sulphate solution to the sample using a pipette...
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...FISH 503 Advanced Limnology (University of Idaho, Moscow Idaho Cam pus) Oxygen Module Winkler titration lab Goal: To familiarize the participants with the Winkler titration of oxygen determination in water; understand principles of the underlying chemistry; to understand standardization procedures of chemical solutions; perform sodium thiosulfate standardization; perform Winkler titrations; examine experimenter error and intra-experimenter error. Examine “kits”. Outcomes: Ability to determine under what conditions Winkler chemistry is appropriate for determination of DO in water; ability to relate details of chemical reactions to and knowledge of indirect determinations; perform titrations and calculate titration standards, as well as mass of DO in samples; assess individual and among individual errors associated with method. General description: You have received a new O2 meter that the person giving to you ensures is ‘perfectly calibrated’ and ‘ready-to-go’. You are heading out on a one-shot chance to sample in the arctic, are you going to trust this person to have gotten it right. How do you check that your probe is actually giving you a believable number (yes does the light in the fridge really turn off when yo close the door?) You will find out in this lab how to check your sensor. Your tasks: 1) Familiarize yourself with the Winkler titration chemistry so you know what you are doing once you get your hands on the bottles and chemicals. 2) Standardize the Sodium thiosulfate...
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...having uncertainty, ambiguity and subjectivity. Analysis of surface water quality plays significant role in environmental impact assessment studies. For qualitative description of surface water quality, number of physical, chemical and biological parameters are taken into consideration, allotted a weightage factor and calculated into an index called water quality index (WQI). Water quality index uses crisp set to analyse water contaminants and hence deals with standing boundary conditions. This paper illustrates use of fuzzy inference system for analysing physical and chemical parameters to assess surface water quality. A water quality index calculated with fuzzy inference system has been developed and discussed. Introduction Determination of status of water quality of a river or any other water sources is highly indeterminate. The current method of determining water quality index which is in practice utilizes statistical approach and is not precise in most of the time. Nowadays environmental protection and water quality management has become an important issue in public policies throughout the world. Moreover, government is concerned about the quality of their environmental resources because of the complexity in water quality data sets. Many countries have introduced a scheme for river water quality monitoring and assessment, examining separate stretches of fresh water. Water Quality Index (WQI) is computed for classification of water wherein the integration of...
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...Topic: Comparative analysis of portable water of Dhaka City Course: ENV 107 Section: 34 Semester: Summer 2016 Prepared by Istiaque Rahman ID: 1611345630 Prepared For Dr. Md. Tajuddin Sikder M. Sc. In Environmental Sciences (JU), Ph. D in Environmental Science (Hokkaido University, Japan) Department of Environmental Science and Management North South University, Dhaka, Bangladesh ABSTRACT Comparative examination of different samples of portable water sources of water in Dhaka city was carried out with a view to assess the different sources of water and determine the water quality of the different sources. The sources of water examined are MUM drinking water, NSU drinking water, NSU tap water, distilled water, Pepsi and waste water. Many parameters were taken in consideration to test the water including physical conditions such as smell, color, turbidity and chemical conditions such as pH, DO, E.coli, TDS and NaCl present in the samples. Finally, a comparative analysis was done to assess the water quality of each samples based on the results from the experiment done. INTRODUCTION Importance of Water: With two thirds of the earth's surface covered by water and the human body consisting of 75...
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...Liqui-Cel® Membrane Contactors are widely used in the soft drink and brewing industries to Control dissolved gasses Gas control is an important concern in the beverage industry. Oxygen in the water can oxidize flavor components and shorten the shelf life of the product. Carbon dioxide can also have an impact on taste and pH of the product. Liqui-Cel Membrane Contactors utilize a hydrophobic polypropylene membrane to remove dissolved gasses from water. Water flows on one side of the membrane and a vacuum or strip gas is passed on the other side of the membrane. By controlling the pressures of gasses in contact with the water, a highly efficient method for gas control can be achieved. Membrane contactors are widely accepted to control gas levels in liquids used in the soft drink and brewing industries. Some of the applications that membranes have been used for in these industries are listed below. Brewing O2 removal from blending water • Oxygen can break down the final product if it is not removed from the water used in the blending process. For this reason, O2 specifications are typically less than or equal to 10-ppb. O2 removal of pushing water • In breweries, large volumes of product is left in DE filters and piping. In order to collect and use the product, the brewery will pump water through the system to “push out” the beer. • The O2 specification here is also less than or equal to 10-ppb. Low O2 concentrations are important because the product will absorb any gasses present...
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...World Bank & Government of The Netherlands funded Training module # WQ - 11 The chemistry of dissolved oxygen measurement New Delhi, May 1999 CSMRS Building, 4th Floor, Olof Palme Marg, Hauz Khas, New Delhi – 11 00 16 India Tel: 68 61 681 / 84 Fax: (+ 91 11) 68 61 685 E-Mail: dhvdelft@del2.vsnl.net.in DHV Consultants BV & DELFT HYDRAULICS with HALCROW, TAHAL, CES, ORG & JPS Table of contents 1 2 3 4 5 6 7 8 Module context Module profile Session plan Overhead/flipchart master Evaluation sheets Handout Additional handout Main text 2 3 4 5 29 31 38 39 HP Training Module File: “ 11 Chemistry of DO measurement.doc” Version 05/11/02 Page 1 1 Module context This module deals with significance and chemistry of dissolved oxygen measurement. Modules in which prior training is required to complete this module successfully and other available, related modules in this category are listed in the table below. While designing a training course, the relationship between this module and the others, would be maintained by keeping them close together in the syllabus and place them in a logical sequence. The actual selection of the topics and the depth of training would, of course, depend on the training needs of the participants, i.e. their knowledge level and skills performance upon the start of the course. No. 1 Module title Basic water quality concepts Basic chemistry concepts Code WQ - 01 • • • • • 3 How to prepare standard solutions WQ - 04 • • • 2 WQ - 02 ...
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