Characters. - A white crystalline heavy powder.

Preparation. - Heat mercury 20 oz. with sulphuric acid 12 fl. oz. in a porcelain vessel, stirring constantly until the metal disappears, then continue the heat until a dry white salt remains.

Reactions. - It is rendered yellow by affusion with water, the subsulphate being formed. Entirely volatilised by heat.

Preparations in which Sulphate of Mercury is used. Hydrargyri Perchloridum. Hydrargyri Subchloridum.