Chromium is a metallic chemical element with the symbol Cr, atomic number 24 and atomic weight 51.9961. It is a silver-grey, lustrous, brittle, hard metal that can be highly polished. Its most important use is in the steel industry where it is a constituent of several alloy steels. It is also used in the production of corrosion-resistant coatings and its compounds are used as mordants in textile dyeing and paint pigments.
The French pharmacist and chemist Nicolas-Louis Vauquelin discovered chromium in 1798 after experimenting with crocoite (a mineral consisting of lead chromate). Here is the method he used in isolating chromium:
- He first added hydrochloric acid to the crocoite in question which precipitated lead.
- He then filtered the lead from the solution and added the filtrate to a charcoal crucible (a container in which substances can be subjected to very high temperatures) which he placed in another crucible made of porcelain which was filled with charcoal powder.
- He then placed the apparatus in a forge for an hour during which a large fire was sustained by a pair of bellows with three pipes.
- After cooling and breaking the porcelain crucible, he found what he described as “a metallic mass of white grey colour, shining, very brittle, and upon the surface of which were many feathered crystals of the same colour perfectly metallic” in the charcoal crucible.
Here is a photograph of high-purity chromium:
[ux_image_box img=”1501″ image_width=”60″ link=”https://en.wikipedia.org/wiki/Chromium” target=”_blank”]
Here is a lithograph of Nicolas-Louis Vauquelin:
[ux_image_box img=”1504″ image_width=”40″ link=”https://www.britannica.com/biography/Nicolas-Louis-Vauquelin” target=”_blank”]