Reinecke's salt is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one ele ...

with the formula NH₄ r(NCS)₄(NH₃)₂� H₂O. The dark-red

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macr ...

line compound is soluble in boiling water,

acetone Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscible wi ...

, and

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a h ...

. The chromium atom is surrounded by six nitrogen atoms in an octahedral geometry. The NH₃ ligands are mutually ''trans'' and the Cr–NCS groups are linear. The salt crystallizes with one molecule of water.

Structure

It was first reported in 1863. NH₄ r(NCS)₄(NH₃)₂is prepared by treatment of molten NH₄SCN (melting point around 145–150 °C) with (NH₄)₂Cr₂O₇.

Use

This salt was once widely used to precipitate primary and secondary

amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent su ...

s as their ammonium salts. Included in the amines that effectively form crystalline precipitates are those derived from the amino acids, including proline and hydroxyproline. It also reacts with Hg²⁺ compounds, giving a red color or a red precipitate.

References

{{reflist Chromium complexes Reagents for organic chemistry Ammine complexes Thiocyanates Chromium(III) compounds Ammonium compounds