The potassium dichromate is a lab reagent that’s chemical formula is [K₂Cr₂O₇]. It 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.
Features of Potassium Dichromate
- Potassium dichromate for analysis EMSURE® ACS, ISO, Reag. Ph Eur
- Synonyms: Potassium bichromate, Potassium pyrochromate
- Chemical Formula: K₂Cr₂O₇
- Boiling point: >500 °C (1013 hPa)
- Density: 2.680 g/cm3 (20 °C)
- Melting Point: 390 °C
- pH value: 3.5 – 5.0 (29.4 g/l, H₂O, 25 °C)
- Bulk density: 1250 kg/m3
- Solubility: 115 g/l
- Categories of danger: carcinogenic, mutagenic, toxic for reproduction, oxidizing, very toxic, corrosive, sensitizing, dangerous for the environment
- Pack Size: 500gm
- Brand: Merck
- Origin: Germany
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Uses of Potassium Dichromate
- The potassium dichromate is mainly used in the production of potassium chrome alum, and in the leather tanning industry.
- Potassium dichromate can be used as a raw material for the manufacturing of chromic acid which is used as an etchant for glass materials and also for the purpose of cleaning glassware. Nowadays its use is very limited because of its hazardous nature.
- It is also used in the construction industry as an ingredient in cement which increases the hardening time of the concrete mixture and improves its density and colour. Long-term exposure to potassium dichromate by construction workers causes skin diseases.
- In the photography industry, it is used as an oxidising agent and in photography screen printing.
- It is also used as a hardening agent for organic solvents like gelatin, dye, carbon black and gum arabic. These hardened solvents find their uses in the creation of metal printing plates used in photomechanical printing processes.
- The solution of potassium dichromate solution with dilute H2SO4 is used for the development of negatives in photography.
- It is also used in screen printing photography because it has the property of tanning leathers and skin on exposure to light.
- Potassium dichromate acts as an excellent chemical reagent in analytical chemistry because of its non-hygroscopic properties. One of the major uses is in the determination of the concentration of ethanol.
- One important application for potassium dichromate is in old police breathalyzer tests for the determination of drink and drive cases.
- When alcohol vapour makes contact with the orange dichromate-coated crystals, the colour changes from Cr(VI) orange to Cr(III) green. The degree of the colour change is directly related to the level of alcohol in the suspect’s breath.
- Schwerter’s solution ( solution of 35% nitric acid and potassium dichromate) is used for the analysis of various metals and their purity. This is more common for silver so it is called the silver test. It also gives different colours for different purity grades of silver.
- Potassium dichromate paper is widely used for the analytical test of sulfur dioxide, as it gives a cloud change from orange to green.
- Many times it is also used for the staining, polishing and tanning of wood which gives it a glossy finish with a rich brown texture.