2. Answer the following

iv. Which steps are involved in manufacture of potassium dichromate from chromite ore ?


The manufacture of potassium dichromate (K2Cr2O7) from chromite ore involves several steps. Chromite ore is a source of chromium, and potassium dichromate is a common chemical compound derived from chromium. Here are the key steps involved in the process:

  1. Mining and Ore Extraction: The process begins with the mining of chromite ore (FeCr2O4), which is the primary source of chromium. This ore is usually found in underground mines.

  2. Ore Processing: The mined chromite ore is processed to remove impurities and convert it into a more usable form. This typically involves crushing the ore and then subjecting it to various chemical and physical processes, such as gravity separation and magnetic separation, to separate the chromite from other minerals.

  3. Conversion to Sodium Chromate: The chromite ore is then mixed with sodium carbonate (Na2CO3) and roasted in the presence of air. This process converts the chromium in the ore into sodium chromate (Na2CrO4), which is water-soluble.

  4. Leaching: The sodium chromate solution is leached to separate it from the insoluble impurities. This step involves dissolving the sodium chromate in water and then separating it from the residue.

  5. Formation of Sodium Dichromate: The sodium chromate solution is further processed to convert it into sodium dichromate (Na2Cr2O7). This is typically done by adding sulfuric acid (H2SO4) to the solution, which reacts with the sodium chromate to form sodium dichromate.

  6. Precipitation of Sodium Dichromate: Sodium dichromate is less soluble in water than sodium chromate. By carefully controlling the pH of the solution and adding additional sodium dichromate, sodium dichromate crystals can be precipitated from the solution.

  7. Conversion to Potassium Dichromate: To obtain potassium dichromate, the sodium dichromate is treated with potassium chloride (KCl). This results in the formation of potassium dichromate (K2Cr2O7) and sodium chloride (NaCl) as a byproduct. The potassium dichromate can then be separated from the solution and purified.

  8. Crystallization and Drying: The potassium dichromate is further purified through crystallization, and the resulting crystals are dried to obtain the final product, potassium dichromate.

  9. Packaging and Storage: The purified potassium dichromate is packaged for distribution and storage. It is important to handle this compound with care, as it is toxic and a strong oxidizing agent.

It’s worth noting that the production of potassium dichromate involves several chemical reactions and processes that require careful control to ensure the purity and safety of the final product. Additionally, the use of chromates and dichromates in industrial processes is subject to environmental regulations due to their toxic nature and potential environmental impact. Proper waste management and disposal are essential in this manufacturing process.