A cooling bath is a mixture used in a laboratory

Laboratory

A laboratory is a facility that provides controlled conditions in which scientific research, experiments, and measurement may be performed. The title of laboratory is also used for certain other facilities where the processes or equipment used are similar to those in scientific laboratories...

 when low temperatures are needed, for example to conduct low-temperature chemical reaction

Chemical reaction

A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...

s (such as when kinetic control of the reaction is desired), to collect highly volatile liquids from distillation

Distillation

Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....

, or in cold trap

Cold trap

In vacuum applications, a cold trap is a device that condenses all vapors except the permanent gases into a liquid or solid. The most common objective is to prevent vapors from a vacuum pump from contaminating the experiment or sample of interest. Cold traps also refer to the application of cooled...

s. It usually consists of a solid that melts or sublimes at a low temperature, or a liquid that boils at a low temperature, mixed with some other substance that modulate the temperature of the bath or improve heat conduction.

Types

The simplest and cheapest cooling bath is an ice/water mixture, which maintains a temperature of 0 °C. For lower temperatures, three main types of cooling baths are typical:

Ice

A slurry of ice

Ice

Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

 and an inorganic salt such as sodium chloride

Sodium chloride

Sodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...

 or calcium chloride

Calcium chloride

Calcium chloride, CaCl2, is a salt of calcium and chlorine. It behaves as a typical ionic halide, and is solid at room temperature. Common applications include brine for refrigeration plants, ice and dust control on roads, and desiccation...

 can provide temperatures down to about −40 °C. The temperature depends on the amount and type of salt used, based on the freezing point depression effect.

Dry ice

A slurry of dry ice

Dry ice

Dry ice, sometimes referred to as "Cardice" or as "card ice" , is the solid form of carbon dioxide. It is used primarily as a cooling agent. Its advantages include lower temperature than that of water ice and not leaving any residue...

 and a suitable organic solvent, such as acetone

Acetone

Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...

, can provide temperatures down to about −100 °C (with diethyl ether

Diethyl ether

Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...

). Temperatures in the range of -12 °C to -78 °C can be conveniently generated with ethylene glycol

Ethylene glycol

Ethylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet-tasting liquid...

/ ethanol / dry ice mixtures.