Potassium chromate - K2CrO4

K₂CrO₄ 

Tarapacaite is the natural, mineral form of potassium chromate. It occurs very rarely and until now is known from only few localities in Atacama Desert.

Potassium Chromate is a yellowish, crystalline, inorganic compound that emits toxic chromium fumes upon heating. Potassium chromate is highly corrosive and is a strong oxidizing agent. This substance is used in the manufacture of dyes and in textile dyeing processes. Potassium chromate primarily affects the nose, throat and lungs causing ulcerations, shortness of breath, bronchitis, pneumonia and asthma but can also affect the gastrointestinal tract, liver, kidneys and immune system. This substance is a known human carcinogen and is associated with an increased risk of developing lung cancer and cancer of the sinonasal cavity.

Application: 

Unlike the less expensive sodium salt, the potassium salt is mainly used for laboratory work in situations where an anhydrous salt is required. It is an oxidizing agent in organic synthesis. It is used 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 an excess silver ions.

It is used in chemical analysis, in making pigments for paints and inks, as a fungicide, and to make other chromium compounds. Potassium chromate is a potassium salt consisting of potassium and chromate ions in a 2:1 ratio. It has a role as a carcinogenic agent and an oxidising agent.

Formula: K₂CrO₄

Molecular Weight: 194.189 g/mol
Form: Yellow powder
CAS Number: 7789-00-6

Density: 2.7320 g/cm³
Synonyms: Chromic acid, dipotassium salt, dipotassium;dioxido(dioxo)chromium, Tarapacaite, Chromate of potash, Chromate of potass, Caswell No. 687