Brine

Brine is water saturated or nearly saturated with salt (NaCl). It is used (now less popular than historically) to preserve vegetables, fish, and meat. Brine is also commonly used to age Feta cheese. Although brine is used in preservation much like sugar or vinegar, it can be used to great effect in transportation. Brine is a common fluid used in the transport of heat from place to place. It is used because the addition of salt to water lowers the freezing temperature of the solution and a relatively great efficiency in the transport can be obtained for the low cost of the material. At a concentration of 23.31%, the freezing point of the solution is lowered to -21 °C (-6 °F), this is called the eutectic point.

Brine is also used to pre-treat roads for winter storms. The solution is poured onto the roadways along with actual salt pellets to create a safer roadway when winter weather is in the forecast.

Brine is also used in removing heat from ice surfaces such as hockey or figure skating rinks. The brine is cycled through the refrigeration plant and returned under the slab of ice at a colder temperature. Brine is used in cruise vessels' cooling systems.

Brines are also used in the offshore oil and gas industry where a pipeline prior to commissioning is flooded with a meg/brine mix to prevent the formation of hydrates on production start up. This is dependent on the well properties. It is useful to refrigeration and heating.

Brine is electrolyzed in the chloralkali process to make sodium hydroxide, chlorine and hydrogen, as well as the hypochlorite and chlorate salts on an industrial scale. In this case, the chloride ions are oxidized to chlorine, while water is reduced to hydrogen gas and hydroxide anions, which, together with the sodium ions already present, give sodium hydroxide on evaporation.

It is also used in the Solvay process to produce sodium carbonate, and in the solution mining of salt from underground deposits. Brines are also used in the pharmaceutical industry.