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.
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 do you find the concentration of COD?
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.
What is the concentration of sulfuric acid used in this COD test?
117048 SupelcoSulfuric acid 95 – 97% for COD determination. Sulfuric acid 95 – 97% for COD determination MSDS (material safety data sheet) or SDS, CoA and CoQ, dossiers, brochures and other available documents.
Which chemical is used in COD test?
potassium dichromate
COD is measured via a laboratory assay in which a sample is incubated with a strong chemical oxidant for a specified time interval and at constant temperature (usually 2 h at 150°C). The most commonly used oxidant is potassium dichromate, which is used in combination with boiling sulphuric acid.
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 basis for the COD test?
The basis for the COD test is that nearly all organic compounds can be fully oxidized to carbon dioxide with a strong oxidizing agent under acidic conditions. The amount of oxidized agent need to completely oxidize the organic material is then compared to the equivalent amount of oxygen.
What is the formula of COD?
6H2O + 20 ml Conc. H2SO4 + 1 Ltr D.W.)
Which method is used for COD?
The traditional chemical oxygen demand (COD) analysis method is the wet chemistry method. This involves a two hour digestion at high heat under acidic conditions in which potassium dichromate acts as the oxidant for any organic material present in a water sample.
How is COD and BOD calculated?
The COD test should be considered an independent measure of the organic matter in a wastewater sample rather than a substitute for the BOD test.
Can I use my COD results to predict my BOD?
| Sample 1: | COD = 2,150 mg/L | BOD = 1,100 mg/L |
|---|---|---|
| Sample 3: | COD = 1,850 mg/L | BOD = 997 mg/L |
| COD ÷ BOD = 1,850 ÷ 997 = 1.86 |
Why h2so4 is used 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.
Which catalyst is used in COD experiment?
Abstract. In this study, 10% CuO/Al2O3 catalyst was used in a catalytic wet-air oxidation process to remove chemical oxygen demand (COD) and color from experimentally designed wastewater containing lignin.
Why Ag2SO4 is used in COD?
The COD analysis uses silver sulfate (Ag2SO4) as a catalyst, mercury sulfate (Hg2SO4) to eliminate chloride interference, ferric ammonium sulfate ((NH4)2. Fe(SO4).
What is COD and how it is measured?
COD is an indicative measure of the amount of oxygen that can be consumed by reactions in a measured solution. It is commonly expressed in mass of oxygen consumed over volume of solution, which in SI units is milligrams per liter (mg/L). A COD test can be used to easily quantify the amount of organics in water.
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.
How do you prepare a COD sample?
Dissolve 9.8 g ferrous ammonium sulfate in a solution of 100 ml of distilled water and 20 ml concentrated Sulfuric acid. Cool the solution and make up the solution to 1000 ml of distilled water. Standardize the solution to determine the actual concentration to calculate the chemical oxygen demand.
How can we prepare 0.1 N potassium dichromate?
Preparation of 0.1 N Potassium dichromate (K2Cr2O7) Solution
- Transfer 6 g of potassium dichromate (K2Cr2O7) to a platinum dish and dry at 120°C for 4 h. Cool in a desiccator.
- Place 4.9 g of the dried K2Cr2O7 in a 1-L volumetric flask, and.
- Add 100 mL of water.
- Store the solution in a glass-stoppered bottle.
What is the molarity of potassium dichromate?
Potassium Dichromate, 0.100 N (N/10), 0.0167 M (M/60), Ricca Chemical | Fisher Scientific.
How is dilution factor calculated in COD?
simply calculate the COD and then multiply the result by the dilution factor. The dilution factor is the total volume of the solution divided by the the stock volume.
Is the oxidising agent used during COD measurement?
This indicated that potassium permanganate was not able to effectively oxidize all organic compounds in water, rendering it a relatively poor oxidizing agent for determining COD. Since then, other oxidizing agents such as ceric sulphate, potassium iodate, and potassium dichromate have been used to determine COD.
How do you make COD standard solution?
Preparation of a COD standard solution:
Dissolve 0.851 g of potassium hydrogen phthalate in a calibrated or conformity-checked 100-ml volumetric flask and make up to the mark with dilution solution. The stock solution prepared according to this procedure has a concentration of 10 000 mg/l COD and 20 g/l Cl–.
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