This website uses cookies to ensure you have the best experience. Learn more

Dissolved Oxygen Essay

3465 words - 14 pages

12.097 Environmental Chemistry of Boston Harbor – IAP 2006

Lab 1:
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 ...view middle of the document...

Oxygen in the water sample oxidizes iodide ion (I-) to iodine (I2)
quantitatively. The amount of iodine generated is then determined by titration with a
standard thiosulfate (S2O3-2) solution. The endpoint is determined by using starch as a
visual indicator. The amount of oxygen can then be computed from the titer: one
mole of O2 reacts with four moles of thiosulfate.

12.097 Environmental Chemistry of Boston Harbor – IAP 2006
At the time of sampling, dissolved oxygen is fixed by the addition of Mn(II) under
basic conditions, resulting in a brown precipitate, manganic hydroxide (MnO(OH)2).
Prior to analysis, the sample is acidified to pH 1.0-2.5. This causes the precipitated
hydroxides to dissolve, liberating Mn(III) ions. Mn(III) ions oxidize previously added
iodide ions to iodine. Iodine forms a complex (I3-) with surplus iodide ions. Iodine
and the complex exist in equilibrium; thus, I3- serves as a reservoir of I2. The iodine
is then titrated with thiosulfate; iodine is reduced to iodide and the thiosulfate is
oxidized to tetrathionate. The stoichiometric equations for the reactions described
above are:
Mn +2 + 2OH − → Mn (OH )2
oxidation of Mn(II) to Mn(III)
2 Mn(OH )2 + O2 + H 2 O → 2 MnO (OH )2
2 Mn(OH )3 + 2 I − + 6 H + → 2 Mn +2 + I 2 + 6 H 2 O oxidation of I- to I2

I 2 + I − ↔ I 3−
I 3− + 2 S 2 O3−2 → 3I − + S 4 O6−2

oxidation of S2O3-2 to S4O6-2; reduction of I3- to I-

The thiosulfate solution is not stable and therefore must be standardized with a
primary standard, typically potassium iodate (KIO3). Standardization is based on the
co-proportionation reaction of iodide with iodate, thereby forming iodine. As
described above, the iodine binds with excess iodide, and the complex is titrated with
thiosulfate. One mole of iodate produces three moles iodine, which are consumed by
six moles of thiosulfate.
IO3− + 8 I − + 6 H + → 3I 3− + 3H 2 O

I 3 + 2 S 2 O3


→ 3 I − + S 4 O6


A note to the student:
The entire method is presented below. It is important that you understand the
complete method from sample collection to analysis. In addition, you might need/
want to repeat this measurement in the future. All reagents will be made before the
lab period. Additionally, the sodium thiosulfate solution will be standardized for you.
If time allows, you may get a chance to do this. You will be responsible for
measuring your own blank and samples. You are responsible for the procedures
described in section 9c and onward.

12.097 Environmental Chemistry of Boston Harbor – IAP 2006
5. Sampling apparatus
a. Sample flasks: Glass stoppered dissolved oxygen bottles (115 mL nominal
capacity – also called “BOD bottles”). 1 clean and dry bottle per sample, blanks
and standard.
b. Volumetric dispensers (or manual volumetric pipettes (disposable, glass)).
c. Four dispensers capable of accurately dispensing 1 mL aliquots. These should be
labeled “Reagent #1”, “Reagent #2” and...

Other assignments on Dissolved Oxygen

How Concentration Affects Rate Of Reaction

639 words - 3 pages 200cm3 of water , which we mixed until all the crystals were dissolved 3. Once this is done then you pour out 50c3,40cm3,30cm3,20cm3,10cm3 of the solution into five same conical flasks ,once this is done you then add water to the other conical flask in 50cm,make sure you label the flasks so that you know which one has so much concentration . 4. After this is done you must now take a beaker and add 35cm3 of concentration hydrochloric acid

Ecosystem Of Coral Reef Essay

2520 words - 11 pages is salty and the reason being is due to the salinity in the water. The two ions found in seawater are chloride and sodium. The salt in the ocean's water has a lot of chemicals in it such as potassium, magnesium sulfate and calcium. There are rocks in the lakes and streams that play a major part in this process. When it rains inland it contains some dissolved carbon dioxide from the surrounding air which causes the rain water to have an acidic

Preparation Of Bis (Acetylacetonato)Copper (Ii)

1374 words - 6 pages ∙3H2O), 1:1ammonia solution, acetyl acetone Procedure : 1. 6g of copper(II) nitrate (Cu(NO3)2∙3H2O) was dissolved in 60cm3 of water, 2. The solution of 1:1 Ammonia was added slowly with stirring until the precipitate first formed has just redissolved. 3. The solution was continuing stirring then 6cm3 of acetyl acetone was added drop by drop into the solution. 4. The crude product was filtered off by using suction filtration

In Cold Blood

4258 words - 18 pages fishes here thai have no blood?" Ruud knew that was impossible because he had learned from textbooks that one trait all vertebrates share is red A few more samples trickled back to Norway, but these were always stored blood, the color of which is due to the presence of oxygen-binding hemoglobin protein in red blood cells. in preservatives that limited the kinds of information Ruud could extract. He Thinking that the veteran was just


2718 words - 11 pages of oxygen. E) is composed of two atoms of helium and one atom of oxygen. 8. The composition of sea water is mostly water molecules and A) calcium. B) iron. C) algae. D) alcohol. E) dissolved salts. 9. Water is sometimes called the: A) molecule of life. D) miracle element. B) universal solvent. E) All of the above C) most significant non-polar molecule. 10. An artesian aquifer is A) a groundwater storage


1865 words - 8 pages ? Explain each. Cohesive and Adhesive Behavior - Cohesion and adhesion in water are caused by the intermolecular attraction between the partial negative oxygen of one water molecule, and the partial positive hydrogen of another molecule. This non-covalent bond is known as a hydrogen bond. Water is strongly cohesive because each molecule may make four hydrogen bonds with other water molecules in a tetrahedral configuration. Surface tension is a

Math Bellevue

5441 words - 22 pages regression line from x = 40 to x = 300. Which of the lines in the figure below is the correct regression line? | | A. | Blue | B. | Yellow | C. | Red | | To plot the line, compute DD = 3.242 minutes when D = 40 meters, and DD = 6.83 minutes when D = 300 meters. | Points Earned: | 0/1 | Correct Answer: | A | Your Response: | C |   | Biochemical oxygen demand (BOD) measures organic pollutants in water by measuring the amount of


4974 words - 20 pages , Turbidity and Conductivity measurements; Estimation of Hardness, Dissolved Oxygen, BOD and COD; Plate Counts and MPN test; Estimation of Fluoride and metals using colorimetric methods, Introduction to advance instruments i.e. Atomic Adsorption Spectroscopy (AAS). Texts/References: 1. C. N Sawyer, P. L McCarty and G. F. Parkin, Chemistry for Environmental Engineers, McGrawHill,1994. 2. APHA, Standard Methods Examination of Water and


3625 words - 15 pages -      Temperature -      Time -      Dose -      Mechanical action   Ozone fading   -    By using this technique, the garment can be bleached. -    Bleaching of denim garment is done in washing machine with ozone dissolved in water. -    Denim garments can also be bleached or faded by using ozone gas in closed chamber. -    In the presence of UV light, there is an interaction between the hydrocarbons, oxides of nitrogen and oxygen that causes


6030 words - 25 pages (14% w/v). The mixture was maintained at 100 °C for 1 h. The reaction was stopped with 0.5 ml of distilled water. Then, the extracted fatty acid methyl esters (FAMEs) were dissolved in heptane for GC analyses. GC analyses were performed on a Hewlett-Packard 5890 Series II gas chromatograph (H.P. Co., Amsterdam, The Netherlands) equipped with a hydrogen flame ionization detector and a capillary column: HP Inovax cross-linked PEG Published


714 words - 3 pages The first ethical issue presented in the ethics game simulation was whether to warn consumers about the contaminated product and what information to provide consumers about the contaminant. The second ethical issue was whether to sell a product that does not meet U.S. safety requirements in a foreign market that has lower safety restrictions. G-BioSport was not required to meet prior approval from the Federal Drug Administration before they

Similar Documents

Overview Of The Cardiovascular And Digestive System

499 words - 2 pages Cardiovascular System The cardiovascular system includes the heart, the blood and the blood vesicles. The heart is a muscular organ that pumps blood around the body by using blood vessels. The blood vessels consist of the arteries, veins and capillaries. The blood carries dissolved oxygen to the body cells and at the same time, it removes the waste products made by respiration. Blood also distributes heat throughout the body, along hormones

The Time Essay

1013 words - 5 pages Blood is the fluid that is transported throughout the whole human body. It carries many nutrients from the digestive tract to the cells, oxygen from the lungs to the cells, waste products from the cells to various organs of excretion, and hormones from secreting cells to other parts of the body. It helps in the distribution of heat formed in the active tissues to all parts of the body. Blood also helps to regulate the acid base balance and to

Lerete Essay

806 words - 4 pages hardness of good quality water should not exceed 270 mg/L (15.5 grains per gallon) measured as calcium carbonate. Water softer than 30-50 mg/L may be corrosive to piping depending on pH, alkalinity and dissolved oxygen. Total HARDNESS: Hardness is the property which makes water form an insoluble curd with soap and is primarily due to the presence of Calcium and Magnesium. Waters which are very hard have no known adverse health effects and may be

Winkkler's Method Essay

2220 words - 9 pages Foundation in Science 7 UTAR FHSC1114 Physical Chemistry Trimester 1 Topic 3: Determination of the amount of dissolved oxygen in a water sample by iodometry – the Winkler’s method ________________________________________________________________________ Introduction: Myriad forms of life exist in lakes, streams and oceans. These creatures depend on dissolved oxygen (D.O.) in water for their life support. Occasionally something will