Determination of some organic thio-compounds by precipitation of mercuric sulphide from mercury(II) ammine complexes--II: determination of thiourea and some of its derivatives

A gravimetric method based on precipitation of mercuric sulphide has been developed for determination of thiourea and some of its derivatives (acetylthiourea and sym-diphenylthiourea). Concentrated nitric acid is added to 0.1M mercuric nitrate, the solution is made alkaline with concentrated ammonia solution and thiourea (dissolved in concentrated ammonia solution), acetylthiourea (dissolved in methanol) or diphenylthiourea (dissolved in acetone) is added and the mixture is boiled. The precipitate is filtered off, washed, and dried at 110 degrees . The determination takes about 40 min. The method gives satisfactory results for thiourea and very good ones for diphenylthiourea and acetylthiourea.