Description
⌕ Enlarge Image
Chromium is one of the transition metals that has a silvery metallic color in its natural solid state. This metal is highly malleable, and it is known for taking on quite a shine through polishing. Chromium has an atomic weight of 51.9961, a melting point of 3465 °F, a boiling point of 4840 °F. Some common uses of chromium include: as a component in metal alloys, to manufacture stainless tell and harden steel compounds, as a coloring emerald green in glass and chrome yellow pigment, and in the tanning of leather.
Isolation
Chromium is found in its pure form in naturals, but it is very rare. Pure chromium for industrial purposes is usually isolated from chromite ore.
⌕ Enlarge Image
Large deposits of chromite ore, FeCr2O3 , is mined and used for chromium isolation reactions. During the isolation process, chromite is oxidized by exposure to the air and heated with liquid alkali; the result of this step is sodium chromate. The sodium chromate is then reacted with water, precipitated out, and reduced with carbon to produce chromium oxide. Further reduction with aluminum and chromium oxide produce pure chromium and aluminum oxide; this last reduction process can also take place using silicon instead of aluminum.
An additional isolation reaction produces chromium electroplating from the chromium oxide. In this process, chromium oxide is reacted with sulphuric acid. Chromium oxide can also be reduced to chromium by heating the chromium oxide and reacting it with charcoal; the resulting compounds from this reaction are carbon dioxide and pure chromium. A process of electrolysis can also separate chromium chloride to pure chromium and chloride.
Often, chromium is not reduced but is converted to ferrochromium for commercial purposes.