Potassium dichromate is obtained by adding to the neutral yellow chromate of potassium in solution, a moderate quantity of one of the stronger acids. Potassium permanganate is  produced by mixing a solution of potassium hydroxide and powdered manganese oxide with an oxidant such as potassium chlorate. 

Potassium dichromate

Potassium dichromate K2Cr2O7 is the most commonly used inorganic chemical reagent as an oxidant in a variety of laboratory and industrial applications. Similarly  hexavalent chromium compounds are acutely and chronically harmful to health. It is a very intense red-orange crystalline ionic solid. This salt is popular in the lab because it does not deliquesce, unlike the more industrially relevant  sodium dichromate salt.

Preparation of Potassium dichromate-

Potassium dichromate (K2Cr2O7) is an orange inorganic chemical reagent. It is mainly used as an oxidizer for alcohol in various laboratories and industries. You can create it in the following process.

• First, fusion of chromite ore FeCr2O4 with sodium carbonate or potassium carbonate in the presence of  air.

• Sodium chromate solution is first filtered and then acidified with  sulfuric acid solution. This allows the orange sodium dichromate solution Na2Cr2O72H2O to crystallize.

2Na2CrO4 + 2H+ 🡪 Na2Cr2O7 + 2Na+ + H2O  

• The sodium dichromate is more soluble than the potassium dichromate, it fuses with KCl  to form orange  potassium dichromate crystals.

Na2Cr2O7 + 2KCl 🡪 K2Cr2O7 + 2NaCl

• At pH 4, dichromate and chromate exist in equilibrium and can be interconverted.

2CrO4 2- + 2H2+ 🡪 Cr2O72- + H2O  

Cr2O7 2- + 2OH- 🡪 2CrO42- 

• The yellow color of chromate changes to orange  dichromate in the presence of an acidic medium, but dichromate is converted to chromate.

2CrO42- + 2H+ 🡪 2HCrO4- (Hydrogen chromate)

2HCrO4-  🡪 Cr2O72- + H2O  Dichromate (orange)

 The chromate ion is tetrahedral and  dichromate ion consists of two tetrahedral sharing at one corner, with Cr-O-Cr bond angle 126 degree.

Properties of potassium dichromate-

• Potassium dichromate is a powerful oxidant in  acidic media.

Cr2O7 2- + 14H+ + 6 electron 🡪 2Cr3+ + 7H2O

• It is very highly corrosive and is a strong oxidizing agent for which it is used in wood preservatives, pigments manufacture and photochemical processes.

• The compound has intense red crystals and is used for dyeing, staining, and tanning etc.
• When heated, potassium dichromate decomposes into potassium chromate, chromium oxide, and oxygen.

 4K2Cr2O7 →  4K2CrO4 +3O2 + 2CrO3

• For medicinal purposes, it is astringent, antiseptic and corrosive. When heated, it releases toxic chrome gas

Uses of Potassium dichromate

It can be used in a variety of applications as an oxidizer and can also be used in the preparation of various products such as paints, waxes and adhesives. As a hexavalent chromium compound, potassium dichromate is highly toxic and carcinogenic.

Potassium permanganate and potassium dichromate are very common in research centers because they are used regularly  in titration methods. Potassium is included in these two mixes as an ingredient, but they look so different that they are definitely recognizable.

Potassium Permanganate

Potassium permanganate is an inorganic compound with a composition of KMnO4. In this sense, the compound is a potassium salt because it has  two particles, K + and MnO4–. Metallic manganese is in a +7 oxidation state. The compound is in a strong state at room temperature and appears as a faint purple strong compound. In addition, it is an important medicine for cleaning up injuries.

Preparation of Potassium Permanganate-

Potassium permanganate (KMnO4) is a deep purple solid composed of two ions, potassium ion (K1) and  permanganate ion (MnO-4). It is a powerful oxidant, has medicinal properties, and  is widely used for wound cleansing and dermatitis treatment. 

• Dissolution of powdered pyrolusite ore (MnO2) with  alkali metal hydroxides such as KOH in the presence of air or an oxidizing agent such as KNO3 results in the formation of dark green potassium manganate (K2MnO4), which is neutral or It becomes imbalanced with acidic media. In the formation of potassium permanganate.

2 MnO2 + 4 KOH + O2 🡪 2K2MnO4  + 2H2O.

3 MnO42- + 4H+  🡪 2MnO4- + MnO2 + 2H2O.

• The potassium permanganate is produced by  the alkaline oxidative fusion of pyrolusite (MnO2) and then by  electrolytic oxidation of manganate (4) ions.

2 MnO2 + O2 + 4KOH  🡪 2K2MnO4 

MnO42- + (electrolytic oxidation)  🡪 MnO4- + e-

Properties of Potassium permanganate –

• Heating potassium permanganate contains potassium manganate, manganese dioxide, and oxygen.

2KMnO4 →  K2MnO4 + MnO2 + O2

• Although nonflammable, it acts as a catalyst for the combustion of flammable substances.
• It has the shape of purple crystals and dissolves in hot water.
• Can be toxic at high concentrations
• Ignite when mixed with glycerin.
• A powerful oxidizer in acidic or alkaline solutions.

Uses of Potassium  permanganate 

Potassium permanganate and potassium dichromate are very common in research centers because they are used regularly  in titration methods. Potassium is included in these two mixes as an ingredient, but they look so different that they are definitely recognizable. 

Conclusion 

Potassium permanganate is an inorganic compound of synthetic formula KMnO4, and potassium dichromate is an inorganic compound of chemical reaction formula K2Cr2O7. Potassium permanganate has a dull purple hue and potassium dichromate has a red-orange hue. Considering the oxidation conditions of the metallic iota in these mixtures, manganese  has a +7 oxidation state with potassium permanganate and chromium  has a +6 oxidation state with potassium dichromate.