Separation of Thiourea and Ammonium Thiocyanate

Ammonium thiocyanate and thiourea are interchangeable isomers. The authors found that treating a mixture of these two with mercuric chloride gives a precipitate of thiourea above pH 4, while the ammonium thiocyanate does not give precipitate below pH 6; thus, the thiourea is precipitated with mercuric chloride at pH 46 to separate from ammonium thiocyanate. The limit of detection of NH4SCN in large amount of (NH2)2CS (1:10000) with mercuric chloride was 1γ. Also, the limit of detection of (NH2)2CS in large amount of NH4SCN (1:10000) with selenious acid was 5γ.