Bases are ionic compounds that contain metal and hydrogen ions. The word "base" came into use in 1717 by French chemist Louis Lémery. Lémery used the word as a synonym for Paracelsus' alchemical concept of a "matrix" in alchemy. Paracelsus proposed natural salts grew as a result of a universal acid mixing with a matrix.
While Lémery may have used the word "base" first, its modern usage is generally attributed to French chemist Guillaume-François Rouelle. Rouelle defined a neutral salt as the product of the union of an acid with another substance that acted as a "base" for the salt. Examples of Rouelle's bases included alkalis, metals, oils, or absorbent earth. In the 18th century, salts were solid crystals, while acids were liquids. So, it made sense to early chemists that the material that neutralized the acid somehow destroyed its "spirit" and allowed it to take solid form.
Bases taste bitter and are slippery when dissolved in water. For example, if you rub household ammonia between your fingers, you will feel the slipperiness of a base. Soap is slippery because it contains a base as well. When placed on red litmus paper, bases will turn blue. Bases also release hydroxide ions in water. Ammonium hydroxide, or ammonia, is a common base used in compounds like nitric acid and is also used in household cleaners.
Just as acids neutralize bases, a base will also neutralize an acid. For example, magnesium hydroxide, found in milk of magnesium, neutralizes stomach acid.
Many bases are encountered as solids. Ammonia is a gas showing basic properties. Aqueous solutions prepared by dissolving bases in water are used in laboratory experiments. Sodium hydroxide (NaOH), potassium hydroxide (KOH) and ammonia solution (NH4OH) can be given as the bases frequently used in the laboratory.
What is a base?
A base is a chemical compound that increases the hydroxyl ion (OH-) concentration of an aqueous solution. For instance, in aqueous solution, sodium hydroxide (NaOH) ionises as follows and contributes to raise the OH- ion concentration.
Based on the strength of releasing OH- ions in the aqueous medium, bases are classified as strong bases and weak bases.
