Research Glossary - S
- salt
- any ionic compound composed of cations (positively charged ions) and anions (negative ions) so that the product is neutral (without a net charge). These component ions can be inorganic such as chloride (Cl−), as well as organic such as acetate (CH3COO−) and monoatomic ions such as fluoride (F−), as well as polyatomic ions such as sulfate (SO42−). Salts are formed when acids and bases react together. Salts that contain a hydroxide ion (OH−) or some other negatively-charged oxygen containing ions (such as carbonate and phosphate) are basic salts; salts that contain a hydrogen ion (H+) are acid salts. Normal salts are those that are neither acid nor basic salts. Zwitterions contain an anionic center and a cationic center in the same molecule but are not considered to be salts; examples include amino acids, many metabolites, peptides and proteins.
The name of a salt starts with the name of the cation (e.g. sodium or ammonium) followed by the name of the anion (e.g. chloride or acetate). Salts are often referred to only by the name of the cation (e.g. sodium salt or ammonium salt) or by the name of the anion (e.g. chloride or acetate).
Common salt-forming cations include:
- ammonium NH4+
- calcium Ca2+
- iron Fe2+ and Fe3+
- magnesium Mg2+
- potassium K+
- pyridinium C5H5NH+
- quaternary ammonium NR4+
- sodium Na+
Common salt-forming anions (and the name of the parent acids in parentheses) include:
- acetate CH3COO− (acetic acid)
- carbonate CO32− (carbonic acid)
- chloride Cl− (hydrochloric acid)
- citrate HOC(COO−)(CH2COO−)2 (citric acid)
- cyanide C≡N− (hydrogen cyanide)
- hydroxide OH− (water)
- nitrate NO3− (nitric acid)
- nitrite NO2− (nitrous acid)
- oxide O2− (water)
- phosphate PO43− (phosphoric acid)
- sulfate SO42− (sulfuric acid)
