For the laboratory preparation of oxygen from any of the compounds like lead dioxide, trilead tetroxide, potassium nitrate, sodium nitrate, potassium chlorate or potassium permanganate, the arrangement of apparatus is, as per the diagram (Fig.13.7).
Oxygen is usually collected over water because the solubility of the gas in water is not high. If the gas is needed dry, then it can be passed through a drying agent, like anhydrous calcium chloride or quick lime, or concentrated sulphuric acid, and then collected over mercury.
