Brine is a solution of salt (usually sodium chloride) in water. In different contexts, brine may refer to salt solutions ranging from about 3.5% (a typical concentration of seawater, or the lower end of solutions used for brining foods) up to about 26% (a typical saturated solution, depending on temperature). Other levels of concentration are called by different names:
|Fresh water||Brackish water||Saline water||Brine|
|< 0.05%||0.05–3%||3–5%||> 5%|
It is held that 0 °F (−17.78 °C and 255.37 Kelvin) was initially set as the zero point in the Fahrenheit temperature scale, as it was the coldest possible temperature that Daniel G. Fahrenheit could reliably reproduce by freezing brine. By reference, seawater usually freezes at -2°C (271.15 K).
|NaCl, wt%||Freezing point (°C)||Density (g/cm3)||Refractive index at 589 nm||Viscosity (cP )|
At 100 °C (373.15 K, 212 °F), saturated sodium chloride brine is about 28% salt by weight i.e. 39.12 g salt dissolves in 100 mL of water at 100 °C. At 0 °C (273.15 K, 32 °F), brine can only hold about 26% salt.
The thermal conductivity of seawater (3.5% dissolved salt by weight) is 0.6 W/mK at 25 °C. The thermal conductivity decreases with increasing salinity and increases with increasing temperature; these graphs and online calculations plot thermal conductivity for varying salinity and temperature:
Electrolysis of brine
- 2 NaCl(aq) + 2 H2O(l) → 2 NaOH(aq) + H2(g) + Cl2(g)
Brine is a common fluid used in large refrigeration installations for the transport of thermal energy from place to place. It is used because the addition of salt to water lowers the freezing temperature of the solution and the heat transport efficiency can be greatly enhanced for the comparatively low cost of the material. The lowest freezing point obtainable for NaCl brine is −21.1 °C (−6.0 °F) at 23.3wt% NaCl. This is called the eutectic point.
In lower temperatures, a brine solution can be used to de-ice or reduce freezing temperatures on roads.
- Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. pp. 8–71, 8–116. ISBN 0-8493-0486-5.
- CRC Handbook of Chemistry and Physics, 63rd Edition 1982-1983.
- Dittman, Gerald L. (February 16, 1977). "Calculation of Brine Properties.". Lawrence Livermore Laboratories. Livermore CA.
- webserver.dmt.upm.es Archived March 21, 2011, at the Wayback Machine.
- Iowa Department of Transportation