Potassium chromate

Dikaliumchromat, Chromate Potassium

Lemon-yellow, crystalline solid

Fixed

2.73 g · cm -3 ( 18 ° C)

965 ° C

1000 ° C.

• Slightly soluble in water ( 637 g · l -1)
• Insoluble in ethanol

Risk

Repealed as carcinogenic

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Potassium chromate is a potassium salt of chromic acid ( H2CrO4 ) with the formula K2CrO4. It is a non-flammable, lemon yellow, toxic and environmentally hazardous solid. The salt is a strong oxidizing agent and is corrosive to skin and mucous membranes.

Production and representation

By the reaction of potassium carbonate and potassium dichromate is produced.

Properties

Anhydrous potassium chromate forms lemon-yellow, prismatic crystals that convert above 670 ° C in a red hexagonal α - modification.

In case of contact with combustible materials, the salt is flammable.

Use

Potassium chromate was almost completely replaced by the cheaper sodium chromate and is only for very specific applications, such as in photography or as an indicator in the titration of sodium chloride by Mohr used ( DAB7 ).

Safety

Potassium chromate is toxic and hazardous to the environment. It leads to irritation and adverse effects on skin and mucous membranes and damaged kidneys, blood and liver. Potassium also acts mutagenic and carcinogenic.

Potassium caused to injured skin poorly healing wounds.

Proof

The chromate anion ( CrO42 ) can be in aqueous solution with metal cations such as Ba2 Pb2 , Hg22 and, depending on the cation yellow to brownish red, precipitation failures:

It should be noted here that in very acidic solutions, the chromate - dichromate equilibrium is shifted increasingly to the dichromate.