Salt (chemistry)


Salt (chemistry)
The blue salt copper(II) sulfate in the form of the mineral chalcanthite

In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations (positively charged ions) and anions (negative ions) so that the product is electrically neutral (without a net charge). These component ions can be inorganic such as chloride (Cl), as well as organic such as acetate (CH3COO) and monatomic ions such as fluoride (F), as well as polyatomic ions such as sulfate (SO42−).

There are several varieties of salts. Salts that hydrolyze to produce hydroxide ions when dissolved in water are basic salts and salts that hydrolyze to produce hydronium ions in water are acid salts. Neutral 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.

Molten salts and solutions containing dissolved salts (e.g., sodium chloride in water) are called electrolytes, as they are able to conduct electricity. As observed in the cytoplasm of cells, in blood, urine, plant saps and mineral waters, mixtures of many different ions in solution usually do not form defined salts after evaporation of the water. Therefore, their salt content is given for the respective ions.

Contents

Properties

Color

Potassium dichromate, a bright orange salt used as a pigment
Manganese dioxide, an opaque black salt

Salts can appear to be clear and transparent (sodium chloride), opaque, and even metallic and lustrous (iron disulfide). In many cases the apparent opacity or transparency are only related to the difference in size of the individual monocrystals. Since light reflects from the grain boundaries (boundaries between crystallites), larger crystals tend to be transparent, while polycrystalline aggregates look like white powders.

Salts exist in many different colors, e.g.,

Most minerals and inorganic pigments as well as many synthetic organic dyes are salts. The color of the specific salt is due to the presence of unpaired electrons in the d-orbital of transition elements.

Taste

Different salts can elicit all five basic tastes, e.g., salty (sodium chloride), sweet (lead diacetate, which will cause lead poisoning if ingested), sour (potassium bitartrate), bitter (magnesium sulfate), and umami or savory (monosodium glutamate).

Odour

Salts of strong acids and strong bases ("strong salts") are non-volatile and odourless, whereas salts of either weak acids or weak bases ("weak salts") may smell after the conjugate acid (e.g., acetates like acetic acid (vinegar) and cyanides like hydrogen cyanide (almonds)) or the conjugate base (e.g., ammonium salts like ammonia) of the component ions. That slow, partial decomposition is usually accelerated by the presence of water, since hydrolysis is the other half of the reversible reaction equation of formation of weak salts.

Degenerationism

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:

Iron(II) oxide (FeO)
Iron(III) oxide (Fe2O3)

Common salt-forming anions (parent acids in parentheses where available) include:

Formation

Solid lead(II) sulfate (PbSO4)

Salts are formed by a chemical reaction between:

See also

References


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Salt (disambiguation) — Salt is an edible mineral used as a flavor enhancer and preservative for food, but may also refer to: Chemistry * Salt (chemistry), a neutral compound composed of ions. * Sodium chloride, the main ingredient in edible salt * Sea salt, is a less… …   Wikipedia

  • salt — [sɔ:lt, sɒlt] noun 1》 (also common salt) sodium chloride, a white crystalline substance which gives seawater its characteristic taste and is used for seasoning or preserving food.     ↘literary something which adds freshness or piquancy. 2》… …   English new terms dictionary

  • salt something out — cause soap to separate from lye by adding salt ■ Chemistry cause an organic compound to separate from an aqueous solution by adding an electrolyte …   Useful english dictionary

  • Chemistry: A Volatile History — is a 2010 BBC documentary on the history of chemistry presented by Jim Al Khalili. It was nominated for the 2010 British Academy Television Awards in the category Specialist Factual. Contents 1 Episode 1 – Discovering the Elements 1.1… …   Wikipedia

  • Salt metathesis reaction — Salt metathesis (from the Greek μετάθεσις transposition ) is a molecular process involving the exchange of bonds between the two reacting chemical species, which results in the creation of products with similar or identical bonding… …   Wikipedia

  • salt — ► NOUN 1) (also common salt) sodium chloride, a white crystalline substance which gives seawater its characteristic taste and is used for seasoning or preserving food. 2) Chemistry any compound formed by the reaction of an acid with a base, with… …   English terms dictionary

  • chemistry — /kem euh stree/, n., pl. chemistries. 1. the science that deals with the composition and properties of substances and various elementary forms of matter. Cf. element (def. 2). 2. chemical properties, reactions, phenomena, etc.: the chemistry of… …   Universalium

  • Salt — This article is about common table salt. For other uses, see Salt (disambiguation). Table salt (NaCl) crystal …   Wikipedia

  • salt — /sɒlt / (say solt), /sɔlt / (say sawlt) noun 1. a crystalline compound, sodium chloride, NaCl, occurring as a mineral, a constituent of sea water, etc., and used for seasoning food, as a preservative, etc. 2. Chemistry a compound which upon… …   Australian English dictionary

  • salt — salt1 saltlike, adj. /sawlt/, n. 1. a crystalline compound, sodium chloride, NaCl, occurring as a mineral, a constituent of seawater, etc., and used for seasoning food, as a preservative, etc. 2. table salt mixed with a particular herb or… …   Universalium


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.