Dichromate

Dichromate (ll) is a divalent inorganic anion obtained by the removal of both protons from dichromic acid. It is a chromium oxoanion and a divalent inorganic anion. It is a conjugate base of a hydrogen dichromate. It is used as a strong oxidizing agent in organic chemistry.

In chemistry, an oxidizing agent is a type of substance that has the ability to oxidize other substances. Oxidation is a phenomenon where a substance can accept electrons from other substances. In simple terms loss of electrons or an increase in the oxidation state of an atom, an ion, or of certain atoms in a molecule. Some of the most common oxidizing agents of dichromate are potassium dichromate and sodium dichromate.

What is dichromate?

Dichromate is a salt, typically red or orange, containing the anion with the chemical formula Cr2O72-.  They are oxyanions of chromium. It is a strong oxidizing agent in organic chemistry. The most common compound known is potassium and sodium dichromate.

Dichromate structure

The formula of dichromate is Cr2O72-. The dichromate structure has 2 chromium ions as central metal ions forming a bridge with a common oxygen atom. It has four double bonds 2 on each chromium ion in such a manner that they are in the opposite direction.

Physical properties of dichromate

The physical properties of dichromate are as follows:

Chemical properties of dichromate

• It reacts with hydrogen sulfide and oxidizes it to sulfur, similarly it oxidizes sulfites to sulfates, chlorides to chlorine, nitrites to nitrates, thiosulphates to sulfates, and Sulfur to stannic salts.

       Cr2O72- + 3H2S + 8H+ → 2Cr3+ + 3S + 7H2O

• Acidified solution of dichromate forms a deep blue color with peroxide to the formation of 

[CrO(O2)2].

                       Cr2O72- + 4H2O2 + 2H+ → 2CrO5 + 5H2O.

Uses of dichromate

• It is used as an oxidizing agent.

• It is used in volumetric examinations.

• Used in photography for hardening of gelatin film.

• Used in the preparation of other chromium compounds such as chrome alum, chrome yellow, and chrome red.

• It is used in coloring and calico printing.

• Used in chrome tanning in the leather industry.

Potassium dichromate

Potassium dichromate is an inorganic chemical compound. It is an orange crystalline solid with the chemical formula K2Cr2O7. It is a crystalline ionic solid, with a bright red-orange color. It is odorless and insoluble in acetone as well as alcohol but dissolves in water.

Properties of potassium dichromate

• Potassium dichromate exists as a solid at room temperature and has an orange-red crystal.

• Potassium dichromate is odorless.

• The melting point of potassium dichromate is 3980c, and its boiling point is 5000c.

• Highly corrosive and non-combustible.

• It is highly soluble in water at a high temperature. But potassium dichromate does not dissolve in alcohol as well as acetone.

Potassium dichromate structure

The chemical formula is K2Cr2O7. It is an ionic compound with two potassium ions(k+) and the negatively charged dichromate ion ( Cr2O7–), in which two hexavalent chromium atoms(with oxidation state +6) are each attached to three oxygen atoms as well as a bridging oxygen atom. 

Potassium dichromate uses

• It is used in coloring and calico printing.

• Potassium dichromate is chiefly utilized in the creation of potassium chrome alum and the cowhide tanning industry.

• In photography, potassium dichromate (K2Cr2O7) is utilized with solid mineral acid as an oxidizing specialist to harden the gelatin film. 

• Commonly it is utilized for the finishing, finishing, and tanning of wood which gives it a gleaming get done with a rich earthy colored surface.

Sodium dichromate

Sodium dichromate is an inorganic compound. It is also known as bichromate of soda, sodium dichromate, or sodium dichromate. Sodium dichromate is a red to reddish-orange crystalline solid. It is known as a powerful oxidizing agent and is highly corrosive. It is odorless and dissolves in water-methanol and ethanol. It is commonly used as a corrosion inhibitor. On heating, it liberates toxic chromium fumes.

Structure of sodium dichromate

The chemical formula is Na2Cr2O7. It is an ionic compound with two potassium ions(Na+) and the negatively charged dichromate ion (Cr2O7–), in which two hexavalent chromium atoms (with oxidation state +6) are each attached to three oxygen atoms as well as a bridging oxygen atom.

Properties of sodium dichromate

Uses of sodium dichromate

• Used as a catalyst.

• Used as an oxidizing agent in the manufacturing of synthetic organic chemicals.

• Used in the refining of petroleum.

• Used in metal treatments such as electro-engraving of copper.

• Used in Colorimetry experiment to determine the amount of copper.

• Used as an insecticide and fungicide.

• Used as a colorant in a glass.

Conclusion

Dichromate (2–) is a divalent inorganic anion obtained by the removal of both protons from dichromic acid. It is a chromium oxoanion and a divalent inorganic anion. It is a conjugate base of a hydrogen dichromate. It is used as a strong oxidizing agent in organic chemistry. It is used as an oxidizing agent. It is used in volumetric examinations.