The dark-red crystalline compound is soluble in boiling water, acetone, and ethanol.

[2] It can be classified as a metal isothiocyanate complex.

The NH3 ligands are mutually trans and the Cr–NCS groups are linear.

[3] NH4[Cr(NCS)4(NH3)2] is prepared by treatment of molten NH4SCN (melting point around 145–150 °C) with (NH4)2Cr2O7.

Included in the amines that effectively form crystalline precipitates are those derived from the amino acids, including proline and hydroxyproline.