Salting out

Salting out is a process that can be used to precipitate proteins out of solution in the process of protein purification, or to precipitate impurities out of solution during the manufacture of inorganic salts like potassium nitrate for gunpowder. This effect is also used in the process of brewing where alcohol is precipitated out of the yeast solution.

Process

The salting out process is based on the principle that the solubility of a protein (or other molecule) in water depends on the concentration of salt. At low salt concentrations, the protein's surface is highly charged and water molecules are attracted to these charges. This keeps the protein dissolved in water. As the salt concentration increases, the salt ions shield the charges on the protein surface, which makes the protein molecules aggregate and precipitate out of solution.

Applications

Salting out has a wide range of applications in both industrial and laboratory settings. It is commonly used in the purification of proteins, as well as in the manufacture of inorganic salts. In the brewing industry, it is used to precipitate alcohol out of yeast solutions.

Factors affecting salting out

Several factors can affect the efficiency of salting out. These include the type of salt used, the concentration of the salt, the temperature of the solution, and the specific properties of the protein or other molecule being precipitated.

See also

• Protein purification
• Inorganic salts
• Brewing