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Potassium dichromate is one of the most widely used chemical reagents inorganic chemistry. It’s commonly used as a strong oxidising agent in various chemical reactions in laboratories and companies. A typical chemical used in oxidation processes is potassium dichromate. It also happens to be one of the most important chromium compounds.
Commercial potassium permanganate is made by combining a solution of potassium hydroxide and powdered manganese oxide with oxidising agents such as potassium chlorate.
Preparation of potassium dichromate (K2Cr2O7)
The following is a step-by-step procedure for extracting K2Cr2O7 from its ore:
- Synthesis of sodium chromate from chrome iron ore
The ore is first pulverised, then mixed with sodium carbonate Na2CO3 and calcium oxide CaO (quick lime), then heated in a reverberatory furnace in sufficient air. This step’s reaction can be written as follows:
4FeO.Cr2O3 + 8Na2CO3 + 7O2 → 8Na2CrO4 + 2Fe2O3 + 8CO2
- Conversion of Na2CrO4 to Na2Cr2O7
We acquire a sodium chromate solution from the first stage. This sodium chromate solution is filtered appropriately using filtration to eliminate iron oxide and other impurities, and then it is reacted with concentrated H2SO4, resulting in sodium chromate being converted to sodium dichromate.
2Na2CrO4 + H2SO4 → Na2Cr2O7 + Na2SO4 + H2O
Sodium dichromate to potassium dichromate conversion
The sodium dichromate obtained in the previous stage is concentrated and heated in the final step, and then this hot concentrated sodium dichromate solution is reacted with potassium chloride KCl to produce potassium dichromate.
This step’s reaction can be written as follows:
Na2Cr2O7 + 2KCl → K2Cr2O7 + 2NaCl
In comparison to sodium chloride NaCl, potassium dichromate is only slightly soluble in water. As a result, when potassium dichromate cools, it separates into crystals.
Physical Properties of Potassium Dichromate
The brilliant red crystals in the compound are used for dyeing, staining, and tanning, among other things.
It can be used as astringent, antiseptic, and caustic in medicine. When heated, it produces deadly chromium fumes.
It is employed in wood preservatives, pigment manufacturing, and photochemical processes since it is highly caustic and a strong oxidising agent.
Potassium Dichromate Uses
Some of the uses of potassium dichromate are:
The most common usage of K2Cr2O7 is in the production of potassium chrome alum, which is widely used in the tanning of leather. This chemical can also be used to make chromic acid. Potassium dichromate is utilised in the cement manufacturing process because it improves the texture and density of the cement mix.
Another notable application of potassium dichromate is in the photography industry, where it is employed as an oxidising agent for photographic screen printing in conjunction with a powerful mineral acid. Because of its non-hygroscopic character, this molecule is also used in various wet tests in analytical chemistry.
Preparation of Potassium Permanganate (KMnO4)
Commercial potassium permanganate combines a solution of potassium hydroxide and powdered manganese oxide with oxidising agents such as potassium chlorate. The mixture is cooked until it has evaporated, then heated in iron pans until it acquires a pasty consistency.
6KOH + 3MnO2 + 6KClO3 → 3K2MnO4 + 6KCl + 3H2O
The potassium manganate (green) is then heated with a huge amount of water, and a current of chlorine, CO2, and ozonized air is circulated through the liquid until permanganate is created. To prevent the MnO2 from breaking down the permanganate.
6K2MnO4 + 3Cl2 → 6KMnO4 (Potassium Permanganate) + 6KCl
The KMnO4 solution is extracted from any concentrated and crystalline MnO2 precipitate. The crystals are dried after centrifugation.
Physical Properties of Potassium Permanganate
It’s a crystalline substance that’s odourless and ranges from purple to magenta.
Water, acetone, acetic acid, methanol, and pyridine are all soluble.
In ethanol and organic liquids, it dissolves.
Potassium permanganate is found as monoclinic prisms that are practically opaque and have a blue metallic sheen.
It has no odour. The taste of an aqueous solution is sweetish astringent. It’s water-soluble, and it’s even more so in boiling water.
Potassium Permanganate Uses
KMnO4 has a wide range of uses. The following are some of the most important applications of potassium permanganate:
In qualitative analysis, potassium permanganate is utilised to determine the permanganate value.
KMnO4 is also utilised as a regeneration chemical to remove hydrogen sulphide and iron in well water treatment.
This substance is also used as a disinfectant to treat skin diseases such as fungal infections in the feet and dermatitis.
The treatment of bacterial infections is another prominent application of potassium permanganate.
Conclusion
Potassium dichromate is a widely used chemical in the industry as an oxidising agent and a precursor to various other chemicals.
Typically, dichromates are made from chromates, which combine chromite ore with sodium/potassium carbonate in the presence of air.
On the other hand, Commercial potassium permanganate combines a solution of potassium hydroxide and powdered manganese oxide with oxidising agents such as potassium chlorate.
