Strontium chloride

Strontium chloride
Names
	IUPAC name Strontium chloride
	Other names Strontium(II) chloride, frozone
Identifiers
CAS Number	10476-85-4 ; 10025-70-4 (hexahydrate) ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:36383 ;
ChEMBL	ChEMBL2219640 ;
ChemSpider	55440 ;
ECHA InfoCard	100.030.870
EC Number	233-971-6;
PubChem CID	61520;
UNII	EKE8PS9J6Z ;
CompTox Dashboard (EPA)	DTXSID6040616 ;
	InChI InChI=1S/2ClH.Sr/h21H;/q;;+2/p-2 Key: AHBGXTDRMVNFER-UHFFFAOYSA-L ; InChI=1S/2ClH.Sr/h21H;/q;;+2/p-2; Key: AHBGXTDRMVNFER-UHFFFAOYSA-L;
	SMILES [Sr+2].[Cl-].[Cl-];
Properties
Chemical 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 (1,605 °F; 1,147 K) (anhydrous) ; 61 °C (hexahydrate)
Boiling point	1,250 °C (2,280 °F; 1,520 K) (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
Magnetic susceptibility (χ)	−63.0·10−6 cm3/mol
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
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 otherwise noted, 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

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 (142 °F). Full dehydration occurs at 320 °C (608 °F).[2]

Structure

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

Strontium chloride is the precursor to other compounds of strontium, such as yellow strontium chromate, strontium carbonate, and strontium sulfate. Exposure of strontium chloride to the sodium salt of the desired anion (or alternately carbon dioxide gas to form the carbonate) leads to precipitation of the salt:[6][2]

SrCl₂ + Na₂CrO₄ → SrCrO₄ + 2 NaCl

SrCl₂ + Na₂CO₃ → SrCO₃ + 2 NaCl

SrCl₂ + H₂O + CO₂ → SrCO₃ + 2 HCl

SrCl₂ + Na₂SO₄ → SrSO₄ + 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

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.[7]

Biological research

Brief strontium chloride exposure induces parthenogenetic activation of oocytes[8] which is used in developmental biological research.

Ammonium storage

A commercial company is using a strontium chloride-based artificial solid called AdAmmine as a means to store ammonium at low pressure, mainly for use in NO_x 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.[9] Earlier company research also considered using the stored ammonium as a means to store synthetic Ammonium fuel under the trademark HydrAmmine and the press name "hydrogen tablet", however, this aspect has not been commercialized.[10] Their processes and materials are patented. Their early experiments used magnesium chloride, and is also mentioned in that article.

References

Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
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
Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
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
"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
Aydoğan, Salih; Erdemoğlu, Murat; Aras, Ali; Uçar, Gökhan; Özkan, Alper (2006). "Dissolution kinetics of celestite (SrSO₄) in HCl solution with BaCl₂". Hydrometallurgy. 84 (3–4): 239–246. doi:10.1016/j.hydromet.2006.06.001.
"Archived copy". Sensodyne. Archived from the original on 2008-09-18. Retrieved 2008-09-05.CS1 maint: archived copy as title (link)
O'Neill GT, Rolfe LR, Kaufman MH. "Developmental potential and chromosome constitution of strontium-induced mouse parthenogenones" (1991) Mol. Reprod. Dev. 30:214-219
Amminex A/S: The solid , retrieved 2013-06-12
Tue Johannesen: "'Solidified' ammonia as energy storage material for fuel cell applications", presentation slides, Amminex , posted at the NH3 Fuel association website in May 2012, retrieved 2013-06-12

External links

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[1] Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8

[Ullmann-2] 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

[Greenwood-3] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.

[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

[hydrometallurgy-6] Aydoğan, Salih; Erdemoğlu, Murat; Aras, Ali; Uçar, Gökhan; Özkan, Alper (2006). "Dissolution kinetics of celestite (SrSO₄) in HCl solution with BaCl₂". Hydrometallurgy. 84 (3–4): 239–246. doi:10.1016/j.hydromet.2006.06.001.

[7] "Archived copy". Sensodyne. Archived from the original on 2008-09-18. Retrieved 2008-09-05.CS1 maint: archived copy as title (link)

[8] O'Neill GT, Rolfe LR, Kaufman MH. "Developmental potential and chromosome constitution of strontium-induced mouse parthenogenones" (1991) Mol. Reprod. Dev. 30:214-219

[9] Amminex A/S: The solid , retrieved 2013-06-12

[10] Tue Johannesen: "'Solidified' ammonia as energy storage material for fuel cell applications", presentation slides, Amminex , posted at the NH3 Fuel association website in May 2012, retrieved 2013-06-12