Strontium's Scarlet Sparkles

Home , Celestine (mineral), Strontianite, Strontium, Strontium carbonate, Strontium chloride

in your element Strontium’s scarlet sparkles From sugar beets to TV screens, François-Xavier Coudert explores the history, applications and perils of the Scottish element, strontium

trontium takes its name from The former occurs in large sedimentary applications, including imitation diamonds the Scottish village of Strontian deposits, from which 300,000 tons of (strontium titanate), glow-in-the-dark toys S(Sròn an t-Sìthein), making it the celestine are mined annually, mostly (europium-doped strontium aluminate), only element named after a place in the from China. and toothpastes for sensitive teeth United Kingdom. Adair Crawford in The first industrial use of strontium was (strontium chloride). 1790 recognized that the ore extracted in the production of sugar from sugar beet One application of element 38, from the lead mines of Strontian, and in the nineteenth century. Beet molasses, however, has stood the test of time: the sold as ‘aerated barytes’, had different a by-product of sugar use of its red flame, described as crimson, chemical properties from the production from sugar scarlet or carmine, depending on the barium minerals known at the time. beet, contains 50% author. Chemical News noted in 1918 that This was confirmed by other sugar by weight. This strontium’s sole employment in the UK was chemists, in particular sugar was extracted in the manufacture of signal lights, flares and Friedrich Gabriel Sulzer in by desugarization using fireworks. Today, pyrotechnics still accounts © KAYCIE D. 2011–2015 D. © KAYCIE 1791 and Thomas Charles Hope the so-called strontian process: for 30% of the use of primary strontium

in 1793, who named this strontium hydroxide Sr(OH)2 compounds, in the form of chloride, sulfate, mineral ‘strontianite’ and reacted with soluble sugars in near- carbonate, nitrate or oxalate. If you see ‘strontites’, respectively. boiling molasses to form poorly soluble purple fireworks, they also likely contain The isolation of strontium strontium saccharate compounds. strontium salts, in combination with copper in its metallic form is credited These were subsequently filtered salts (which emit blue light). to Sir Humphry Davy in 1808. and recovered by cooling and In the human body strontium is Earlier that year, Jöns Jacob exposure to carbonation. absorbed in the same manner as its Berzelius and Magnus Martin Strontium hydroxide was neighbour in group 2, calcium, and af Pontin had performed an then regenerated by mostly deposited in the bones. This makes electrolysis of calcium oxide at calcination in the presence strontium fairly innocuous, and it has a mercury electrode to of steam. Nowadays, even been investigated for the prevention produce a calcium– desugarization is instead and treatment of bone diseases such as mercury amalgam. performed using a osteoporosis. Concurrently however this Learning of this similar lime-based process, or through also makes its longest-lived radioactive result, Davy applied ion-exclusion chromatography. isotope 90Sr — generated by nuclear the new technique to four The second large-scale application reactors and nuclear tests — dangerous different alkaline earths and subsequently of strontium was in colour television as it promotes bone cancer. In controlled proceeded to distil the mercury off, thus cathode ray tubes, accounting for up to amounts, 89Sr and 90Sr have also found use isolating a small quantity of the elements 75% of US strontium consumption in in radiotherapy for the treatment of cancers that he named barium, strontium, the latter part of the twentieth century. It that have spread to the bone. calcium, and magnium (now known was used in the faceplate glass to block Aside from anthropogenic applications, as magnesium). X-ray emissions without compromising element 38 is also involved in a biological Strontium is a soft silvery or yellowish the transparency of the tube. Strontium riddle. The Acantharea class of protozoa metal that behaves in a similar manner carbonate was added to the glass melt, have skeletons made of celestine, to the other alkaline earth metals in where it was converted to strontium oxide. puzzling scientists as to the evolutionary group 2. Although abundant in the Earth’s With replacement of cathode ray tubes by benefits behind this peculiar choice of crust — ranking 15th at 340 ppm, very flat-panel displays, the largest remaining building material. ❐ close to barium — relatively few strontium consumer of strontium compounds is the minerals are known. The most common production of ferrite ceramic magnets. FRANÇOIS-XAVIER COUDERT is at CNRS

are celestine (strontium sulfate, SrSO4, Strontium ferrite, SrFe12O19, is among the and Chimie ParisTech, PSL Research named for its delicate blue color) and most common ferrite permanent magnets, University, Paris, France.

strontianite (strontium carbonate, SrCO3). used for devices such as refrigerator e-mail: [email protected] magnets, loudspeakers and small electric Twitter: @fxcoudert motors. Other uses of strontium in our daily lives correspond more to niche Corrected after print: 29 October 2015 Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs 940 NATURE CHEMISTRY | VOL 7 | NOVEMBER 2015 | www.nature.com/naturechemistry

Correction In the In Your Element article ‘Strontium’s scarlet sparkles’ (Nature Chem. 7, 940; 2015), the years in the first paragraph were incorrect. These were corrected in the online versions after print on 29 October 2015.

1034 NATURE CHEMISTRY | VOL 7 | DECEMBER 2015 | www.nature.com/naturechemistry