Two crystalline forms are known, both being very similar to the corresponding potassium sulfate. Orthorhombic β-K2CrO4 is the common form, but it converts to an α-form above 66 °C.[2] These structures are complex, although the sulfate adopts the typical tetrahedral geometry.[3]

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  Structure of β-K2CrO4.

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  Coordination sphere of one of two types of K+ site.

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  The environment about the tetrahedral CrO42− center in β-K2CrO4.

Production and reactions

It is prepared by treating potassium dichromate with potassium hydroxide.

In solution, the behavior of potassium and sodium dichromates are very similar. When treated with lead(II) nitrate, it gives an orange-yellow precipitate, lead(II) chromate.

Applications

Unli

ke the less expensive sodium salt, potassium salt is mainly used for laboratory work in situations where an anhydrous salt is required.[2] It is as an oxidizing agent in organic synthesis. It is used as in qualitative inorganic analysis, e.g. as a colorimetric test for silver ion. It is also used as an indicator in precipitation titrations with silver nitrate and sodium chloride (they can be used as standard as well as titrant for each other) as potassium chromate turns red in the presence of excess of silver ions.