Preparation Of Potassium Dichromate

A widely used chemical compound or salt in inorganic chemistry is potassium dichromate. It is primarily used in laboratories and businesses as an oxidising agent in various chemical reactions. Potassium dichromate is very commonly used in oxidation processes. It’s also one of the most significant chromium compounds. Potassium dichromate is also known as the dipotassium salt of dichromic acid and is a potassium salt. The most popular method for potassium dichromate is to use chromates made by reacting chromite ore with sodium/potassium carbonate. We’ll take a closer look at potassium dichromate in the sections below.

Potassium Dichromate Formula

Potassium Dichromate Formula : K₂Cr₂O₇

Molar Mass : 294.185 g/mol

Potassium Dichromate is an ionic molecule which consists of two potassium ions that are positively charged (K⁺) and a dichromate ion that is negatively charged (Cr₂O₇^2-). In this compound, two hexavalent chromium ions are connected to three oxygen atoms and a bridging oxygen atom.

Potassium Dichromate Properties

When it decomposes, it becomes a vivid red-orange crystalline solid with a 2.676 g/mL density, a melting point of 398 °C, and a boiling temperature of 500 °C. 

It has no odour and is very water-soluble.

Potassium dichromate has a refractive index of 1.738.

It has a triclinic crystalline structure and a tetrahedral coordination geometry for the core atom of chromium.

Preparation of Potassium Dichromate 

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. 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

Compared to sodium chloride NaCl, potassium dichromate is only slightly soluble in water. As a result, when potassium dichromate cools, it separates into crystals.

Uses of Potassium Dichromate

The following are some of the most common industrial applications for potassium dichromate:

• Potassium dichromate is primarily utilised in the making of potassium chrome alum and leather tanning.
• Potassium dichromate is used as a starting material for producing chromic acid, which is used to manufacture glass and clean glassware. Due to its harmful nature, its use is restricted nowadays.
• It’s also utilised as a cement component and used by construction workers as it increases the hardening time and improves the density and colour of the concrete mix.
• Because it produces an orange-to-green cloud shift, potassium dichromate paper is commonly used for sulphur dioxide analytical testing.
• It’s frequently used for wood staining, polishing, and tanning, giving it a glossy finish with a rich brown texture.

Potassium Dichromate Health Hazards

The following are some of the most common health hazards of potassium dichromate:

• Potassium dichromate is a cancer-inducing substance. Long-term exposure to this substance can harm respiratory organs and possibly result in death in rare situations.
• Since it’s cancer-causing, consuming even a small amount of potassium dichromate can cause death. 
• This salt is highly corrosive, and swallowing even a small amount of it can harm the oesophagus, stomach and intestines.
• Ingestion or exposure to potassium dichromate can also cause vomiting, diarrhoea and excess urination.

Conclusion

Potassium dichromate is always treated with extreme caution and attention, as it can be harmful to people if exposed for an extended time. It is found in an ionic solid crystalline condition and has a beautiful, vivid red-orange colour. The non-deliquescent characteristic of potassium dichromate, as opposed to other industrially important salts like sodium dichromate, is widespread in analytical chemistry and industry. The most popular method for potassium dichromate is to use chromates made by reacting chromite ore with sodium/potassium carbonate.