Alkali is a chemical substance, usually referring to compounds such as hydroxides and carbonates of alkali metals or alkaline earth metals.

The chemical composition of bases mainly involves alkali metal and alkaline earth metal elements, as well as anions such as hydroxides and carbonates formed by combining with them. The following will introduce in detail the composition, properties and applications of bases in chemistry and daily life.

The main components of bases:

Alkali metals: Alkali metals are the elements in the first group of the periodic table, including lithium (Li), sodium (Na), and potassium (K) , rubidium (Rb), cesium (Cs) and francium (Fr). These metals have low density, low melting point, and extremely reducing properties. They occur in nature as cations and are commonly found in minerals, soil, and the earth's crust.

Alkaline earth metals: Alkaline earth metals are elements in the second group of the periodic table, including beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). Alkaline earth metals have higher densities and melting points and are also commonly found in nature.

Hydroxide: A base combines with a hydroxide ion (OH-) to form a hydroxide, often called a base hydroxide. For example, sodium hydroxide (NaOH, common caustic soda) is a common base. Hydroxide produces an alkaline solution in water, the alkalinity of which is determined by the concentration of hydroxide ions.

Carbonates: Alkali metals and alkaline earth metals combine with carbonate ions (CO3^2-) to form alkali metal carbonates or alkaline earth metal carbonates. For example, sodium hydrocarbonate (NaHCO3, baking soda) and sodium carbonate (Na2CO3, barite) are both alkaline substances.

Properties and applications of alkalis:

Alkalinity: Alkali are alkaline, and their aqueous solutions are alkaline. Alkaline solutions will cause the acid indicator to change color, usually blue or bluish-green.

Neutralization reaction: Bases can react with acids to produce salts and water. This neutralization reaction is often used in chemical experiments and industry to adjust pH and control reaction conditions.

Cleaning agents and fertilizers: Some alkaline compounds, such as sodium hydroxide and potassium hydroxide, are used as cleaning agents to remove grease and impurities. Sodium carbonate is also often used as agricultural fertilizer to improve the acidity and alkalinity of the soil.

Glass and ceramic manufacturing: Sodium hydroxide and sodium carbonate play an important role in glass and ceramic manufacturing and can adjust the properties and melting point of substances.

Food industry: Alkaline substances are widely used in the food industry, such as baking soda for baking, sodium hydroxide for food processing, etc.

Pharmaceuticals and cosmetics: Alkaline substances also have certain applications in pharmaceutical preparations and cosmetics. For example, sodium hydroxide is used to make soaps and detergents, and sodium carbonate is used as a regulator in pharmaceutical preparations.