Sodium carbonate anhydrous is white powder or fine grains, easily soluble in water, and the aqueous solution is alkaline. It has strong hygroscopicity and can absorb moisture in the air and form hard lumps. Sodium carbonate decahydrate is a colorless crystal, which will lose water of crystallization and become sodium carbonate monohydrate when placed in air at room temperature. Whether it is sodium carbonate decahydrate or sodium carbonate monohydrate, it will become anhydrous sodium carbonate when heated. Sodium carbonate is very stable and does not decompose easily when heated. Acid can release carbon dioxide:
Na2CO3+2HCl====2NaCl+H2O+CO2↑
Sodium carbonate solution can also absorb carbon dioxide and become sodium bicarbonate:
Na2CO3+H2O+CO2====2NaHCO3
Of the three kinds of soda, sodium carbonate is the most widely used. It is a very important chemical product, is an important raw material for glass, soap, textile, paper, tanning and other industries. It is also used in the metallurgical industry and for water purification. It can also be used in the manufacture of other sodium compounds. As early as in the 18th century, it was listed as one of the basic chemical raw materials - three acids and two bases - together with sulfuric acid, hydrochloric acid, nitric acid and caustic soda. In daily life, soda also has many uses, for example, it can be used directly as a detergent, and adding some soda when steaming steamed buns can neutralize the acids produced during fermentation.
Pharmaceutical industry has a wide range of uses, can be used as a digestive agent and acidulant; food industry, can be used as raw materials for baking powder and refreshing beverages; in the plastics and rubber industry, can be used as a foaming agent; in the fire can be used as a fire-fighting agent, in addition to tanning, dyeing and finishing, agriculture, such as dipping seeds.