Strontium chromate
Crystal structure | ||||||||||||||||
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__ Sr 2+ __ Cr 6+ __ O 2− | ||||||||||||||||
Crystal system |
monoclinic |
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Space group |
P 2 1 / n (No. 14, position 2) |
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Lattice parameters |
a = 706.5 pm, b = 737.5 pm, c = 674.1 pm, β = 103.08 ° |
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General | ||||||||||||||||
Surname | Strontium chromate | |||||||||||||||
Ratio formula | SrCrO 4 | |||||||||||||||
Brief description |
lemon yellow solid |
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External identifiers / databases | ||||||||||||||||
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properties | ||||||||||||||||
Molar mass | 203.61 g mol −1 | |||||||||||||||
Physical state |
firmly |
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density |
3.89 g cm −3 |
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Melting point |
approx. 500 ° C (decomposition) |
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solubility |
slightly soluble in water (1.2 g l −1 at 15 ° C) |
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safety instructions | ||||||||||||||||
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Authorization procedure under REACH |
of particular concern : carcinogenic ( CMR ); subject to approval |
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MAK |
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Toxicological data | ||||||||||||||||
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 .
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
- ↑ 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) .
- ↑ 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 .
- ↑ Entry in the SVHC list of the European Chemicals Agency , accessed on July 17, 2014.
- ↑ Entry in the register of substances subject to authorization of the European Chemicals Agency , accessed on July 17, 2014.
- ↑ 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).
- ↑ Swiss Accident Insurance Fund (Suva): Limit values - current MAK and BAT values (search for chromium (VI) compounds ), accessed on October 27, 2015.
- ↑ a b G. Wyrouboff: About the crystal form of some dichromates. In: Journal for Crystallography and Mineralogy. 1894, 22, 207. Full Text
- ↑ Thomas Brock, Michael Groteklaes, Peter Mischke: Textbook of paint technology. Vincentz, Hannover 2000, ISBN 3-87870-569-7 , p. 155.
- ^ 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.
- ↑ 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)