Chromic Thiocyanate, Cr(SCN)3, is prepared by dissolving freshly precipitated chromic hydroxide in thiocyanic acid and evaporating the green-violet solution over sulphuric acid, or by concentrating a solution of chromithiocyanic acid either by heating or over sulphuric acid. It is obtained as a grey, amorphous, deliquescent mass, which readily dissolves in water to form a violet solution. When freshly prepared, the solution does not answer to the ordinary precipitation reactions for the Cr•• and SCN' ions. However, hydrolytic dissociation gradually takes place, especially under the influence of sunlight; the solution becomes green, and precipitates are obtained with silver nitrate and ammonia solutions. It is soluble in the chief organic solvents.
Ammoniated compounds, of composition Cr(NH3)2(SCN)3.H2O; Cr(NH3)2(SCN)3.2H2O; NH4CNS.Cr(NH3)2(SCN)3; NH4CNS. Cr(NH3)4(SCN)3; Cr(NH3)2(SCN)4.NH4I, have been prepared.
Thiocyano salts of chromium with organic bases, e.g. pyridine and ethylenediamine, have also been obtained. |