Reinecke's salt is NH₄[Cr(SCN)₄(NH₃)₂], or ammoniumtetrathiocyanatodiamminechromate(III) (CAS number : 13573-16-5). It consists of dark-red crystals, soluble in boiling water and ethanol. Its molecular weight is 354.47 and its melting point 268-272°C Quartz crystal A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... Ethanol, also known as ethyl alcohol or grain alcohol, is a flammable, colorless chemical compound, one of the alcohols that is most often found in alcoholic beverages. ...

Chromium is here in the 3+ oxidation state, surrounded by six ligands in an octahedral geometry; the NH₃ ligands are mutually trans. The oxidation state or oxidation number is defined as the sum of negative and positive charges in an atom, which indirectly indicates the number of electrons it has accepted or donated. ... It has been suggested that this article or section be merged with Ligand (biochemistry). ...

According to Organic Syntheses, NH₄[Cr(SCN)₄(NH₃)₂] is prepared by treatment of molten NH₄SCN (ca. 145–150 °C) with (NH₄)₂Cr₂O₇.

This salt was once widely used to precipitate primary and secondary amines as their ammonium salts. Included in the amines that effectively form insoluble precipitates are those derived from the amino acids, including proline and hydroxyproline. It is also a reacting agent on Hg²⁺-compounds, giving a red color or a red precipitate. Ammonia Amines are organic compounds and a type of functional group that contain nitrogen as the key atom. ... Fumes from hydrochloric acid and ammonia forming a white cloud of ammonium chloride Ammonium is also an old name for the Siwa oasis in western Egypt. ... L-Proline is one of the twenty proteinogenic units which are used in living organisms as the building blocks of proteins. ... 4-Hydroxyproline, or hydroxyproline(C5H9O3N), is an uncommon amino acid, abbreviated as HYP, e. ...

References

• Reinecke, Annalen. vol. 126, page 113ff (1863).
• Dakin, H. D. Organic Syntheses, Coll. Vol. 2, p.555 (1943); Vol. 15, p.74 (1935).