The Probert Encyclopaedia of Science & Technology

ALKALI

Alkali is a term first used to designate the soluble parts of the ashes of plants, especially of sea-weed. Now the term is applied to various classes of bodies having the following properties in common: (1) solubility in water; (2) the power of neutralizing acids, and forming salts with them; (3) the property of corroding animal and vegetable substances; (4) the property of altering the tint of many colouring matters thus, they turn litmus, reddened by an acid, into blue; turmeric, brown; and syrup of violets and infusion of red cabbages, green. The alkalis may be regarded as water in which part of the hydrogen is replaced by a metallic radicle. The caustic alkalis are strong alkalis which have a powerful corrosive action on the skin, and the common ones are potassium hydroxide or caustic potash, sodium hydroxide or caustic soda, and lithic hydroxide. A solution of ammonia in water is termed ammonia hydroxide or volatile alkali. It is a much feebler alkali than the others, and when the solution is heated all the ammonia is driven off. Other alkalis are calcium hydroxide or slaked lime, a solution of which in water is known as lime water; barium hydroxide and strontium hydroxide, derived from the metals barium and strontium.
Research Alkali