Strontium hydroxide

Crystal structure
__ Sr 2+      __ OH -
General
Surname	Strontium hydroxide
other names	Strontian hydrate STRONTIUM HYDROXIDE ( INCI )
Ratio formula	Sr (OH) 2
Brief description	colorless and odorless crystals
External identifiers / databases
CAS number 18480-07-4 (anhydrous) 1311-10-0 (octahydrate) 21800-33-9 (monohydrate) EC number 242-367-1 ECHA InfoCard 100.038.501 PubChem 87672 ChemSpider 79094 Wikidata Q132428
properties
Molar mass	121.63 g mol −1 (anhydrous) 265.76 g mol −1 (octahydrate)
Physical state	firmly
density	3.63 g cm −3 (anhydrous) 1.90 g cm −3 (octahydrate)
Melting point	375 ° C (anhydrous) 100 ° C (octahydrate)
boiling point	Decomposes at 710 ° C
solubility	poor in water (20 g l −1 at 20 ° C, octahydrate) insoluble in acetone
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 314 EUH: 071 P: 260-280-303 + 361 + 353-305 + 351 + 338
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Strontium hydroxide is the hydroxide of the alkaline earth metal strontium . The empirical formula is Sr (OH) ₂ .

presentation

Strontium hydroxide can be produced by the reaction of strontium with water . Strontium hydroxide and hydrogen are produced .

${\displaystyle \mathrm {Sr+2\ H_{2}O\rightarrow Sr(OH)_{2}+H_{2}\uparrow } }$

Furthermore, strontium hydroxide is formed by the reaction of strontium oxide with water with a strong heat development .

${\displaystyle \mathrm {SrO+H_{2}O\rightarrow Sr(OH)_{2}} }$

Because of its poor solubility, the octahydrate can be prepared from any strontium salt (preferably the nitrate or chloride salt because of their high solubility) by adding a strong base such as sodium hydroxide or potassium hydroxide in an aqueous solution by precipitation.

${\displaystyle \mathrm {Sr(NO_{3})_{2}\cdot 4H_{2}O+2\ KOH+4\ H_{2}O\rightarrow Sr(OH)_{2}\cdot 8H_{2}O+2\ KNO_{3}} }$

properties

The salt forms colorless, transparent crystals . In the crystal structure of strontium each Sr ²⁺ - ion of seven OH ^- ions at an average distance of 2.6 angstroms surrounded.

When dissolved in water, strontium hydroxide is a medium-strength base . In this state it absorbs carbon dioxide (CO ₂ ) from the air with the formation of strontium carbonate . Strontium hydroxide is more soluble in water than the hydroxides of calcium and magnesium . It is less toxic than barium hydroxide .

The octahydrate crystallizes in the tetragonal crystal system in the space group P 4 / ncc (space group no. 130) with the lattice constants a = 901.7  pm and c = 1160.3 pm. When heated, the water of crystallization is released in three stages - first a hexahydrate is formed, then a monohydrate and finally the anhydrate , which also crystallizes in the tetragonal crystal system.

use

Strontium hydroxide is a pH control agent in hair removal products. Strontium hydroxide used to be used in the sugar industry to purify molasses .

Individual evidence

1. ↑ Entry on STRONTIUM HYDROXIDE in the CosIng database of the EU Commission, accessed on February 17, 2020.
2. ↑ ^{a b c d e f g} Entry on strontium hydroxide in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .
3. ↑ ^{a b c d e} Richard C. Ropp: Encyclopedia of the Alkaline Earth Compounds . Newnes, 2012, ISBN 0-444-59553-8 , pp. 122 ( limited preview in Google Book search).
4. ↑ Georg Brauer (Ed.), With the collaboration of Marianne Baudler a . a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume II, Ferdinand Enke, Stuttgart 1978, ISBN 3-432-87813-3 , p. 927.
5. ^ H. Ost: Textbook of Technical Chemistry , published by Robert Oppenheim, Berlin, 1890, p. 369ff.