Preparation of chlorine hydrate
Chlorine is dissolved in water at 0°C, forming a thin slurry which is then filtered through a glass filter funnel surrounded by a jacket cooled with ice water. The obtained chlorine hydrate is placed in one arm of a thick-wall U tube and the tube is sealed off. The chlorine hydrate is decomposed by heating (into liquid chlorine under its own pressure and chlorine-saturated water) and the chlorine formed is condensed by immersing the other arm of the U tube in a refrigerant. Then the refrigerant is removed while the other side of the tube, which contains water saturated with chlorine, is immersed in a vessel full of cold water. After some time large, very glittering, pale-yellow crystals of chlorine hydrate are formed in this arm.
Handbook of Preparative Inorganic Chemistry, by G Brauer, V I, 274, 1965