Sulphates

Metal sulphates

1. Preparation of soluble metal sulphates

Soluble sulphates can be prepared in the laboratory by dissolving a metal, a carbonate, a hydroxide or an oxide in dilute H$_2$SO$_4$

2. Preparation of insoluble sulphates

Insoluble sulphates can be prepared by adding dilute sulphuric acid to lead or barium ions

Chemical properties

1. All sulphates react with barium chloride to give a white precipitate which is insoluble in dilute HCl
2. The sulphates of iron (II), copper (II) and zinc (called green, blue and white vitriol respectively) decompose when heated strongly to give the oxide of the metal, sulphur dioxide, sulphur trioxide and water
3. The sulphates of sodium, potassium, magnesium and calcium don't decompose on heating

Uses of sulphates

1. Sodium sulphate is used to treat wood pulp in the manufacture of paper
2. Anhydrous CaSO$_4$ is used as a source of sulphur dioxide for the manufacture of sulphuric acid
3. Ammonium sulphate is an important fertilizer
4. Aluminium sulphate is used in the purification of sewage as it precipitates proteins
5. CuSO$_4$ (copper (II) sulphate) is used as fungicide i.e. destroyer of fungi on plants
6. Also it is used as an electrolyte for electroplating copper