Typical desiccants consist of silica gel, and molecular sieves. Common desiccants include phosphorus pentoxide and silica gel. Other molecular sieves are used as desiccants (some examples include activated charcoal and silica gel). Another form of electronic dry box technology utilizes multi-porous molecular sieve desiccants to adsorb moisture. Lithium chloride and lithium bromide are hygroscopic and are used as desiccants for gas streams. Sodium-potassium alloys are used as desiccants in drying solvents prior to distillation. For example, desiccants absorb water, drying out (desiccating) the surrounding materials. Glycols are also used as liquid desiccants for natural gas and in air conditioning systems. Because of this, anhydrous salts containing alkali metal cations are often used as desiccants. Although some desiccants are chemically inert, others are extremely reactive and require specialized handling techniques. Commonly encountered pre-packaged desiccants are solids that absorb water. This moisture and humidity control technology is renewable without having to replace desiccants. Industrially, desiccants are widely used to control the level of water in gas streams. The desiccants can be dried and reused. The enthalpy exchange is accomplished through the use of desiccants.