Chlorine is usually prepared in the laboratory from hydrochloric acid, which is a convenient source of chlorine. When concentrated hydrochloric acid is gently heated with the oxidizing agent, such as Mn02′ KMnO, or KCI03, chlorine gas is produced.
In this method Mn02′ is taken in a round bottom flask, as shown in the figure fitted with a cork, containing a delivery tube. Concentrated hydrochloric acid is added in the flask over Mn02. On gentle heating greenish yellow chlorine gas comes
out which is collected by the upward displacement of air in a gas jar through the delivery tube. Since it is a poisonous gas so efficient ventilation in the laboratory is necessary.