Preparation of a COD standard solution: Dissolve 0.851 g of
What is the reference standard solution used in COD analysis?
. Most commonly, a 0.25 N solution of potassium dichromate is used for COD determination, although for samples with COD below 50 mg/L, a lower concentration of potassium dichromate is preferred.
How do you make a standard solution of potassium hydrogen phthalate?
Preparation of KHP Standard Solution:
Purity of the Potassium KHP is 99.9%. Therefore to prepare a 1000 mgC/l standard solution, add 2.13g of KHP in a flask and add enough DIW to make it 1 litre solution. Note that the quantities required change with the % purity of the chemical used.
What is COD standard?
COD is defined as the amount of oxygen equivalents consumed in the chemical oxidation of organic matter by strong oxidant (e.g., potassium dichromate).
Why potassium dichromate is used in COD?
Currently, most COD tests use potassium dichromate as the oxidant. Potassium dichromate is a hexavalent chromium salt that is bright orange in color and is a very strong oxidant. Between 95-100% of organic material can be oxidized by dichromate.
How COD is calculated?
There is a formula for calculating COD. Consider the formula for COD calculation: (a – b) X C X 8,000 / the volume of the sample in mL. Let “a” represent the titrant used for your sample expressed in mL. Let “b” represent the titrant used for your blank sample in mL.
Why do we use h2so4 in COD?
Chemical Oxygen Demand (COD) 1% Silver Sulphate in Sulphuric Acid (conc.) provides the primary and secondary digestion catalysts for oxidation of carbon during chemical oxidation.
How do you make a potassium standard solution?
To prepare this standard, add 1.91 grams of reagent-grade potassium chloride to a 1 liter volumetric flask about half full of distilled water. Swirl the flask to dissolve the solid and fill to the mark with distilled water. Cap the flask and invert several times to mix the solution.
How do you find the standard solution?
You will need to calculate:
- M, the molar mass of the compound used as the primary standard M(compound) = sum of the molar mass of each element multiplied by the number of atoms present in the formula.
- n, the amount in moles of the compound you used as the primary standard n = m ÷ M.
How do you make a standard solution accurate?
Making a standard solution
- It must be available in a highly pure state.
- It must be stable in air.
- It must be easily soluble in water.
- It should have a high molar mass.
- In solution, when used in volumetric analysis, it must undergo complete and rapid reaction.
What is the COD effluent standard?
The effluent standards for biochemical oxygen demand (BOD) exclusively apply to the effluents discharged into public waters other than seas and lakes, the effluent standards for chemical oxygen demand (COD) exclusively apply to the effluents discharged into seas and lakes.
How do you determine COD in water samples?
The COD test uses a chemical (potassium dichromate in a 50% sulfuric acid solution) that “oxidizes” both organic (predominate) and inorganic substances in a wastewater sample, which results in a higher COD concentration than BOD concentration for the same wastewater sample since only organic compounds are consumed
How do you reduce COD in wastewater treatment?
You can reduce COD and BOD by adding hydrogen peroxide to the wastewater solution. The hydrogen peroxide will chemically attack the organics in the wastewater, degrading them and reducing the measured COD and BOD.
Why glass beads are used in COD?
Test for Chemical Oxygen Demand:
Add some glass beads to prevent the solution from bumping into the flask while heating.
How do you make potassium dichromate solution for COD?
1. Potassium dichromate (K2Cr2O7) Solution: Add 6.13 gm Potassium dichromate (previously dried at 105 °C for at least two hours) into 800 ml distilled water. Shake the flask well to dissolve the content and make up the solution to 1000 ml and mix well.
What is the limitation of COD?
One of the main limitations of the COD test is its inability to differentiate between biodegradable and biologically inert organic matter on its own. The use of chemicals such as chromium and strong acids produce hazardous liquid waste, which requires careful disposal.
What is the value of COD?
The COD value indicates the amount of oxygen which is needed for the oxidation of all organic substances in water in mg/l or g/m3. The COD (Chemical Oxygen Demand) is closely related to the laboratory standard method named Dichromate-Method.
What is the COD of water?
Chemical oxygen demand (COD) is the amount of dissolved oxygen that must be present in water to oxidize chemical organic materials, like petroleum. COD is used to gauge the short-term impact wastewater effluents will have on the oxygen levels of receiving waters.
How do you determine COD and BOD?
Testing for BOD involves incubating a sealed water sample at 20C for five days, followed by measuring the difference in oxygen content before and after incubation. COD measures how much DO is consumed by the oxidation of organic matter and inorganic compounds such as ammonia or nitrite under controlled conditions.
How do you make sulfuric acid reagent for COD?
7.1 Pipet a 50.0 mL aliquot of sample not to exceed 800 mg/L of COD into a 500 ml, flat bottom, Erlenmeyer flask. Add HgSO4 (6.4) in the ratio of 10 mg to 1 mg chloride, based upon the mg of chloride in the sample aliquot and 5 mL of sulfuric acid (6.7). Swirl until all the mercuric sulfate has dissolved.
What causes high COD in water?
COD increases as the concentration of organic material increases. It also increases if inorganic compounds susceptible to oxidation by the oxidant (typically dichromate) are present. Water with high COD typically contains high levels of decaying plant matter, human waste, or industrial effluent.
Justin Shelton is a professional cook. He’s been in the industry for over 10 years, and he loves nothing more than creating delicious dishes for others to enjoy. Justin has worked in some of the best kitchens in the country, and he’s always looking for new challenges and ways to improve his craft. When he’s not cooking, Justin enjoys spending time with his wife and son. He loves exploring new restaurants and trying out different cuisines.