Strontium chromate

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Crystal structure
Unit cell of strontium chromate
__ Sr 2+ __ Cr 6+ __ O 2−
Crystal system

monoclinic

Space group

P 2 1 / n (No. 14, position 2)Template: room group / 14.2

Lattice parameters

a = 706.5 pm, b = 737.5 pm, c = 674.1 pm, β = 103.08 °

General
Surname Strontium chromate
Ratio formula SrCrO 4
Brief description

lemon yellow solid

External identifiers / databases
CAS number 7789-06-2
EC number 232-142-6
ECHA InfoCard 100.029.220
PubChem 24599
Wikidata Q735561
properties
Molar mass 203.61 g mol −1
Physical state

firmly

density

3.89 g cm −3

Melting point

approx. 500 ° C (decomposition)

solubility

slightly soluble in water (1.2 g l −1 at 15 ° C)

safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary
06 - Toxic or very toxic 08 - Dangerous to health 09 - Dangerous for the environment

danger

H and P phrases H: 302-330-317-335-340-350-361-410
P: 201-260-262-263-273-281
Authorization procedure under REACH

of particular concern : carcinogenic ( CMR ); subject to approval

MAK
  • Germany / EU: 5 μg m −3 (calculated as chromium)
  • Switzerland: 5 μg m −3 (calculated as chromium)
Toxicological data

3120 mg kg −1 ( LD 50ratoral )

As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Strontium chromate is a chemical compound from the group of strontium compounds and chromates .

presentation

Strontium chromate can be precipitated from an aqueous solution of strontium chloride and potassium chromate .

The synthesis from strontium carbonate and chromic acid is also described.

properties

Strontium chromate is a lemon yellow, non-flammable solid that is sparingly soluble in water. It decomposes from a temperature of around 500 ° C. Strontium together with sulfate ions strontium sulfate .

When heated with strontium carbonate , the hexavalent chromium is reduced to the pentavalent one, and strontium chromate (V) Sr 3 (CrO 4 ) 2 is formed .

Strontium dichromate is formed with chromic acid .

Strontium chromate crystallizes in the monazite structure, i.e. in the monoclinic crystal system in the space group P 2 1 / n (space group no.14 , position 2) with the lattice parameters a = 706.5  pm , b = 737.5 pm, c = 674 , 1 pm and β = 103.08 °. In the unit cell there are four  formula units . Template: room group / 14.2

use

Strontium chromate, like zinc chromate, is used as a corrosion- preventing primer for zinc , magnesium , aluminum and alloys in the aircraft industry. It is also for the production of chromium - pigments used. Since, like all chromates, it is classified as carcinogenic, its use is limited today.

Individual evidence

  1. a b c d e f g h i Entry on strontium chromate in the GESTIS substance database of the IFA , accessed on July 23, 2016(JavaScript required) .
  2. Entry on strontium chromate in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
  3. Entry in the SVHC list of the European Chemicals Agency , accessed on July 17, 2014.
  4. Entry in the register of substances subject to authorization of the European Chemicals Agency , accessed on July 17, 2014.
  5. European Parliament and Council: Directive (EU) 2017/2398 of the European Parliament and of the Council of 12 December 2017 amending Directive 2004/37 / EC on the protection of workers from the risks related to exposure to carcinogens or mutagens at work ( Text with EEA relevance). In: http://data.europa.eu/eli/dir/2017/2398/oj . EU, December 12, 2017, accessed April 5, 2018 (English, German).
  6. Swiss Accident Insurance Fund (Suva): Limit values ​​- current MAK and BAT values (search for chromium (VI) compounds ), accessed on October 27, 2015.
  7. a b G. Wyrouboff: About the crystal form of some dichromates. In: Journal for Crystallography and Mineralogy. 1894, 22, 207. Full Text
  8. Thomas Brock, Michael Groteklaes, Peter Mischke: Textbook of paint technology. Vincentz, Hannover 2000, ISBN 3-87870-569-7 , p. 155.
  9. ^ KA Wilhelmi, O. Jonsson: X-Ray Studies on Some Alkali and Alkaline-Earth Chromates (V). In: Acta Chem. Scand. 1965, 19, doi : 10.3891 / acta.chem.scand.19-0177 , pp. 177-184.
  10. H. Effenberger, F. Pertlik: "Four monazite type structures: comparison of SrCrO 4 , SrSeO 4 , PbCrO 4 (crocoite), and PbSe0 4 " in Zeitschrift für Kristallographie 1986 , 176 , pp. 75 - 83. Full text (PDF File; 718 kB)