Potassium DiChromate (5kg)
Potassium dichromate, K2Cr2O7, is a common inorganic chemical reagent, most commonly used as an oxidizing agent in various laboratory and industrial applications. As with all hexavalent chromium compounds, it is acutely and chronically harmful to health. It is a crystalline ionic solid with a very bright, red-orange color. The salt is popular in the laboratory because it is not deliquescent, in contrast to the more industrially relevant salt sodium dichromate.
Potassium dichromate is usually prepared by the reaction of potassium chloride on sodium dichromate. Alternatively, it can be also obtained from potassium chromate by roasting chromite ore with potassium hydroxide. It is soluble in water and in the dissolution process it ionizes:
- K2Cr2O7 → 2 K+ + Cr2O2−7Cr2O2−7 + H2O ⇌ 2 CrO2−4 + 2 H+
Like other chromium(VI) compounds (chromium trioxide, sodium dichromate), potassium dichromate has been used to prepare “chromic acid” for cleaning glassware and etching materials. Because of safety concerns associated with hexavalent chromium, this practice has been largely discontinued.
Potassium dichromate occurs naturally as the rare mineral lopezite. It has only been reported as vug fillings in the nitrate deposits of the Atacama desert of Chile and in the Bushveld igneous complex of South Africa.
Potassium dichromate is one of the most common causes of chromium dermatitis; chromium is highly likely to induce sensitization leading to dermatitis, especially of the hand and fore-arms, which is chronic and difficult to treat. Toxicological studies have further illustrated its highly toxic nature. With rabbits and rodents, concentrations as low as 14 mg/kg have shown a 50% fatality rate amongst test groups. Aquatic organisms are especially vulnerable if exposed, and hence responsible disposal according to the local environmental regulations is advised.
As with other Cr(VI) compounds, potassium dichromate is carcinogenic. The compound is also corrosive and exposure may produce severe eye damage or blindness. Human exposure further encompasses impaired fertility, heritable genetic damage and harm to unborn children.