Strontium chloride

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Strontium chloride
Strontium chloride hexahydrate
Identifiers
CAS number 10476-85-4 YesY, 10025-70-4 (hexahydrate)
PubChem 61520
ChemSpider 55440 YesY
UNII EKE8PS9J6Z YesY
EC number 233-971-6
ChEBI CHEBI:36383 YesY
ChEMBL CHEMBL2219640
Jmol-3D images Image 1
Properties
Molecular formula SrCl2
Molar mass 158.53 g/mol (anhydrous)
266.62 g/mol (hexahydrate)
Appearance White crystalline solid
Density 3.052 g/cm3 (anhydrous, monoclinic form)
2.672 g/cm3 (dihydrate)
1.930 g/cm3 (hexahydrate)
Melting point 874 °C (anhydrous)
61 °C (hexahydrate)
Boiling point 1250 °C (anhydrous)
Solubility in water anhydrous:
53.8 g/100 mL (20 °C)
hexahydrate:
106 g/100 mL (0 °C)
206 g/100 mL (40 °C)
Solubility ethanol: very slightly soluble
acetone: very slightly soluble
ammonia: insoluble
Refractive index (nD) 1.650 (anhydrous)
1.594 (dihydrate)
1.536 (hexahydrate) [1]
Structure
Crystal structure Deformed rutile structure
Coordination
geometry
octahedral (six-coordinate)
Hazards
EU Index Not listed
Main hazards Irritant
Flash point Non-flammable
Related compounds
Other anions Strontium fluoride
Strontium bromide
Strontium iodide
Other cations Beryllium chloride
Magnesium chloride
Calcium chloride
Barium chloride
Radium chloride
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Strontium chloride (SrCl2) is a salt of strontium and chloride. It is a typical salt, forming neutral aqueous solutions. Like all compounds of Sr, this salt emits a bright red colour in a flame; in fact it is used as a source of redness in fireworks. Its chemical properties are intermediate between those for barium chloride, which is more toxic, and calcium chloride.

Preparation[edit]

Strontium chloride can be prepared by treating strontium hydroxide or strontium carbonate with hydrochloric acid:

Sr(OH)2 + 2 HCl → SrCl2 + 2 H2O

Crystallization from cold aqueous solution gives the hexahydrate, SrCl2·6H2O. Dehydration of this salt occurs in stages, commencing above 61 °C. Full dehydration occurs at 320 °C.[2]

Structure[edit]

The solid adopts a deformed rutile structure.[3] In the vapour phase the SrCl2 molecule is non-linear with a Cl-Sr-Cl angle of approximately 130°.[3] This is an exception to VSEPR theory which would predict a linear structure. Ab initio calculations have been cited to propose that contributions from d orbitals in the shell below the valence shell are responsible.[4] Another proposal is that polarisation of the electron core of the strontium atom causes a distortion of the core electron density that interacts with the Sr-Cl bonds.[5]

Uses[edit]

Strontium chloride is the precursor to other compounds of strontium, such as yellow strontium chromate, which is used as a corrosion inhibitor for aluminium. The precipitation proceeds analogously to the related, isostructural sulfate:[2]

SrCl2 + Na2CrO4 → SrCrO4 + 2 NaCl

Strontium chloride is often used as a red colouring agent in pyrotechnics. It imparts a much more intense red colour to the flames than most other alternatives. It is employed in small quantities in glass-making and metallurgy. The radioactive isotope strontium-89, used for the treatment of bone cancer, is usually administered in the form of strontium chloride. Sea water aquaria require small amounts of strontium chloride, which is consumed in the production of the exoskeletons of certain plankton.

Dental care[edit]

SrCl2 is useful in reducing tooth sensitivity by forming a barrier over microscopic tubules in the dentin containing nerve endings that have become exposed by gum recession. Known in the U.S. as Elecol and Sensodyne, these products are called "strontium chloride toothpastes", although most now use potassium nitrate instead which works as a nerve calming agent rather than a barrier.[3]

Biological research[edit]

Brief strontium chloride exposure induces parthenogenetic activation of oocytes[6] which is used in developmental biological research.

Ammonium storage[edit]

A commercial company is using a strontium chloride-based artificial solid called AdAmminetm as a means to store Ammonium at low pressure, mainly for use in NOx emission reduction on Diesel vehicles. They claim that their patented material can also be made from some other salts, but they have chosen strontium chloride for mass production.[7] Earlier company research also considered using the stored ammonium as a means to store synthetic Ammonium fuel under the trademark HydrAmminetm and the press name "hydrogen tablet", however this aspect has not been commercialized.[8] Their processes and materials are patented. Their early experiments used magnesium chloride, and is also mentioned in that article.

References[edit]

  1. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
  2. ^ a b J. Paul MacMillan, Jai Won Park, Rolf Gerstenberg, Heinz Wagner, Karl Köhler, Peter Wallbrecht "Strontium and Strontium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH: Weinheim. DOI 10.1002/14356007.a25 321
  3. ^ a b Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0080379419. 
  4. ^ Ab initio model potential study of the equilibrium geometry of alkaline earth dihalides: MX2 (M=Mg, Ca, Sr, Ba; X=F, Cl, Br, I) Seijo L., Barandiarán Z J. Chem. Phys. 94, 3762 (1991) doi:10.1063/1.459748
  5. ^ "Ion model and equilibrium configuration of the gaseous alkaline-earth dihalides" Guido M. and Gigli G. J. Chem. Phys. 65, 1397 (1976); doi:10.1063/1.433247
  6. ^ O'Neill GT, Rolfe LR, Kaufman MH. "Developmental potential and chromosome constitution of strontium-induced mouse parthenogenones" (1991) Mol. Reprod. Dev. 30:214-219
  7. ^ Amminex A/S: The solid [1], retrieved 2013-06-12
  8. ^ Tue Johannesen: "'Solidified' ammonia as energy storage material for fuel cell applications", presentation slides, Amminex [2], posted at the NH3 Fuel association website in May 2012, retrieved 2013-06-12

External links[edit]