Alkalis are hydroxides of alkaline, alkaline-earth metals and ammonium. Perfectly soluble bases in water concern them. OH− anions and a cation of metal are formed at dissociation of alkalis.
In a periodic system hydroxides of metals of subgroups Ia and IIa (since calcium), for example, Ba(OH)2 (caustic barite), KOH (caustic potassium), NaOH (caustic rubbed) carrying the narrow-minded name "caustic alkalis" belong to alkalis. Caustic alkalis are called hydroxides of NaOH sodium, lithium of LiOH, RbOH rubidium, GAME potassium and CsOH caesium. They represent white, solid and very hygroscopic substances. Alkalis are the strong bases which are well dissolved in water with considerable heat release at reaction. Solubility in water and force of the basis increase at increase in radius of a cation in each group of a periodic system. The strongest alkalis are caesium hydroxide in the Ia group and radium hydroxide in the IIa group. The water solution of gas-ammonia which is called liquid ammonia is a weak alkali. Extinguished lime is also sodium alkali. In addition, caustic alkalis can be dissolved in methanol and ethanol. All alkalis in a firm state absorb water and carbon dioxide from air (and in a condition of solution), gradually turning into carbonates. At important chemical property – abilities of formation of salts in reaction with acids of alkali became widespread in the industry. Can carry electric current therefore they are also called electrolytes. It is possible to receive alkalis by impact of water on oxides of alkaline metals or by electrolysis of chlorides. Properties of alkalis: dissolve fat, some of them can dissolve animal and vegetable fabrics, destroy clothes and irritate the skin, can interact with some metals (aluminum), protect steel from corrosion. Alkalis and acids are dangerous, they need to be stored only in the special vessels designated by labels and not in drinking tanks at all. During the work it is necessary to put on goggles.