Sr - Strontium
|Chemical Element||Strontium||Melting Point °C||217|
|Chemical Symbol||Sr||Boiling Point °C||685|
|Atomic Number||38||Density g/cm3||4.8|
|Atomic Weight||87.62||Oxide||SeO2 and SeO3|
Strontium is a silvery-white, relatively soft metal, which is a member of Group 2, also known as the Alkaline Earth Group of the Periodic Table, and is the 16th most abundant element in the Earth’s crust. The bulk metal is protected to a certain degree by an oxide film, but even so, it has to be stored under paraffin as it is highly reactive, tarnishing rapidly when exposed to air. The metal will burn in air if ignited, and burns with a crimson flame; also strontium reacts vigorously with water, producing hydrogen. When finely powdered, if strontium comes into contact with air, it will spontaneously ignite to produce both strontium oxide and strontium nitride.
Strontium was first identified and named in 1789 by the English scientist, Adair Crawford. Crawford came across strontium after a new stone had been found in a lead mine in Strontian, on the west coast of Scotland. The stone eventually ended up with Adair Crawford, who had received it from a mineral specimen dealer. Believing that the mineral was in fact a barium mineral, he passed it on to Crawford, as he knew he was interested in baryta (barium oxide) for its medicinal purposes. Crawford analysed this stone and came to the conclusion that it was a new ‘earth ‘, which he named strontia (strontium oxide). When Crawford published a paper on his research in 1790, he inspired Thomas Charles Hope of Edinburgh to begin a fuller investigation, eventually concluding that there was a new element present. Strontium was not isolated until 1808 by Humphry Davy, using the electrolysis of a mixture of strontium chloride and mercury oxide, the same process that he had used for the isolation of barium, sodium and potassium.
The main producers of the element are UK, Mexico, Turkey and Spain, who together produce 140,000 mt per year. The total reserve is unassessed, and there is little demand for the element due to its high price and similar properties to calcium and barium.
Strontium occurs in nature forming 0.034% of igneous rock in the form of celestite and carbonate strontianite. Celestite is found in sedimentary deposits, which are of sufficient size to justify the development of mining facilities.
Principle uses include pyrotechnics for fireworks and warning flares, due to the brilliant red colour it burns. Also strontium carbonate is used in special TV and computer screen glass and as a ‘getter’ to remove the last traces of air in a vacuum.
- Emsley, John. Nature’s Building Blocks, An A-Z Guide to the Elements, New Edition, Oxford University Press, 2011
- Gray, Theodore. The Elements, A Visual Exploration of Every Known Atom in the Universe, Black Dog & Leventhal Publishers, Inc, NY, 2009
- Stwertka, Albert. A Guide to the Elements, 3rd Edition, Oxford University Press, 2012