Reinecke salt

Structural formula
General
Surname	Reinecke salt
other names	Ammonium tetrathiocyanato diammine chromate (III) Ammonium pure nacrate
Molecular formula	NH 4 [Cr (SCN) 4 (NH 3 ) 2 ]
Brief description	dark red crystals
External identifiers / databases
CAS number 13573-16-5 13573-17-6 (hydrate) EC number 237-003-3 ECHA InfoCard 100.033.625 PubChem 44134924 ChemSpider 21106473 Wikidata Q808801
properties
Molar mass	336.43 g mol −1 354.47 g mol −1 (hydrate)
Physical state	firmly
Melting point	268–272 ° C (decomposition)
solubility	soluble in hot water and ethanol
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 302-312-332-410 P: 261-280-304 + 340-301 + 312-501
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

The Reinecke salt is a complex compound of trivalent chromium with the constitutional formula NH ₄ [Cr (SCN) ₄ (NH ₃ ) ₂ ]. It forms dark red crystals that are soluble in hot water and ethanol . The salt was first produced in 1863 by Albert Reinecke from Detmold by fusing ammonium thiocyanate and potassium dichromate .

properties

The salt consists of an ammonium ion and a complex anion, which consists of a Cr ³⁺ ion as the central atom and six ligands . The complex is coordinated in an octahedral manner.

Reinecke salt

Hg 2+ precipitated with Reinecke salt forms a flaky pink precipitate.

use

The Reinecke salt is used in analysis to detect cations . For example, with mercury (II) ions, a poorly soluble, light red precipitate of so-called mercury (II) pure nectar is formed:

${\displaystyle \mathrm {Hg^{2+}+2\ NH_{4}[Cr(SCN)_{4}(NH_{3})_{2}]\longrightarrow } }$ ${\displaystyle \mathrm {Hg[Cr(SCN)_{4}(NH_{3})_{2}]_{2}\downarrow +2\ NH_{4}^{+}} }$

Copper (I) ions form a yellow, poorly soluble precipitate:

${\displaystyle \mathrm {Cu^{+}+NH_{4}[Cr(SCN)_{4}(NH_{3})_{2}]\longrightarrow } }$ ${\displaystyle \mathrm {Cu[Cr(SCN)_{4}(NH_{3})_{2}]\downarrow +NH_{4}^{+}} }$

The detection with Reinecke salt is very sensitive. This method can also be used for quantitative determination via photometry . If, for example, pure mercury (II) is precipitated in the presence of thiourea , a complex is formed which is soluble in ketones and which can be photometrically measured at 520-540 nm .

In addition to inorganic cations, a large number of reactions with organic cations are now known, in particular with ammonium ions of primary and secondary amines .

Individual evidence

1. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Inorganic Compounds, pp. 4-48.
2. ↑ ^{a b c} Entry on Reinecke salt. In: Römpp Online . Georg Thieme Verlag, accessed on November 12, 2014.
3. ↑ ^{a b c} data sheet ammonium tetrathiocyanatodiammine chromate (III) from AlfaAesar, accessed on May 8, 2017 ( PDF )(JavaScript required) .
4. ^ Academy of Sciences in Göttingen (ed.): Messages from the Royal. Society of Sciences and the Georg August University in Göttingen . Dieterichsche Verlagbuchhandlung, Göttingen 1867, p. 394 ( full text in Google Book Search).
5. ↑ Albert Reinecke: About Rhodanchromammonium -verbindungen. Annalen der Chemie und Pharmazie, Volume 126, Pages 113-118 (1863). doi : 10.1002 / jlac.18631260116 .
6. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 , p. 1452.
7. ↑ Jander-Blasius: Textbook of analytical and preparative inorganic chemistry. 5th edition, S. Hirzel, Stuttgart-Leipzig 1965, pp. 263, 272.
8. ↑ Bruno Lange, Zdenĕk J. Vejdĕlek: Photometric analysis. Verlag Chemie Weinheim 1980, p. 222.
9. ↑ Tim Peppel, Christin Schmidt, Martin Köckerling: Synthesis, Properties, and Structures of Salts with the Reineckate Anion, [Cr ^III (NCS) ₄ (NH ₃ ) ₂ ] ^- , and Large Organic Cations. Journal for inorganic and general chemistry 2011, 637, 1314–1321, doi : 10.1002 / zaac.201100091 .