CsCl

Cesium chloride (CsCl) is an inorganic compound composed of Cs+ and Cl− in a 1:1 ratio. It forms colorless to white crystalline solids that are highly soluble in water.

CsCl crystallizes in the cesium chloride structure (CsCl-type or B2), a simple cubic lattice with Cs+ and Cl− occupying alternating positions. Each ion is eight-coordinate, surrounded by eight counterions from the opposite lattice. The unit cell contains two formula units. In water, CsCl dissociates into Cs+ and Cl− and conducts electricity.

Melting point is about 645 °C. The solid dissolves in water to give an electrically conducting solution when dissolved; molten CsCl also conducts electricity, reflecting its ionic character.

Preparation and handling: Commercially produced by reacting CsOH with HCl, CsCl can also be formed by the direct reaction of Cs metal with Cl2. Purification is typically achieved by recrystallization from water or intermediate salt routes. It is a hygroscopic salt that should be stored in a dry environment.

Uses: CsCl is widely employed as a laboratory reagent and as a source of Cs+ and Cl− in various chemical syntheses. A notable application is in density-gradient ultracentrifugation, where CsCl solutions are used to form buoyant-density gradients for separating DNA, RNA, and other macromolecules. It also serves as a standard reference material and calibrant in certain analytical procedures.

Safety: CsCl is of moderate toxicity if ingested and can disturb electrolyte balance; handle with appropriate lab safety precautions, including gloves and eye protection, and avoid inhalation of dust. It should be stored away from incompatible materials and kept in a tightly closed container.