Sodium carbonate, also known as soda ash, is also called baking soda or soda by some people in daily life. Today, I hereby publish an article to distinguish easily confused names.
1. Soda
Soda is a transliteration of soda, and its chemical formula is Na2CO3. It has many names. Its scientific name is sodium carbonate and its popular name is soda ash. Those with crystal water are called hydrated sodium carbonate, including sodium carbonate monohydrate (Na2CO3 · H2O), sodium carbonate heptahydrate (Na2CO3 · 7H2O) and sodium carbonate decahydrate (Na2CO3 · 10H2O).
Among the three kinds of soda, sodium carbonate is the most widely used. It is a very important chemical product and an important raw material for glass, soap, textile, papermaking, tanning and other industries. It is also used in metallurgical industry and purified water. It can also be used in the manufacture of other sodium compounds. As early as the 18th century, it was 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 directly used as a detergent. When steaming steamed bread, add some soda to neutralize the acidic substances produced in the fermentation process.
2. Baking soda
The chemical formula of baking soda is NaHCO3. It also has many names. Its scientific name is sodium bicarbonate. It is also called weighing sodium carbonate or acid sodium carbonate. In addition to baking soda, there are baking soda, fermentation soda and heavy alkali.
Baking soda is a white crystal, soluble in water, and the aqueous solution is weakly alkaline. In hot air, it can decompose slowly, releasing part of carbon dioxide; Fully liberated carbon dioxide when heated to 270 ℃:
It can also react with acids (such as hydrochloric acid) to release carbon dioxide:
These properties of baking soda make it have many important uses in production and life. In fire extinguishers, it is one of the raw materials that produce carbon dioxide; In the food industry, it is a main raw material of fermentation powder; It is also a common raw material in the manufacture of cool drinks; Medically, it is a kind of medicament for treating gastric acid excess.
3. Bicarbonate of soda
Baking soda is the common name of sodium thiosulfate, also known as hypo. The hydrate contains five crystal waters (Na2S2O3 · 5H2O), so it is also called sodium thiosulfate pentahydrate.
Baking soda is a colorless and transparent crystal, which is easily soluble in water, and the aqueous solution is weakly alkaline. It loses crystal water due to weathering in dry air above 33 ℃.
It is relatively stable in neutral and alkaline solutions and will decompose rapidly in acidic solutions:
Sodium bicarbonate has strong complexing ability and can form complex with silver bromide:
According to this property, it can be used as a fixer. During the phase washing, the excessive sodium bicarbonate reacts with the silver bromide in the non photosensitive part of the negative to convert it into soluble, and the AgBr is removed to fix the developing part.
Baking soda also has strong reducibility, which can reduce chlorine and other substances:
Therefore, it can be used as dechlorination agent for bleached cotton fabrics. Similarly, iodine stains on fabrics can also be removed with it. In addition, baking soda is also used for tanning leather, electroplating and extracting silver from ore.
The above three kinds are the three commonly used "sodas". Besides, sometimes "smelly soda" is mentioned.
Odorous soda is the common name of sodium sulfide, with the chemical formula of Na2S, also known as odorous alkali, yellow alkali and sulfide alkali. It has a bad smell. Soluble in cold water, very soluble in hot water, slightly soluble in alcohol.
Sodium sulfide is an inorganic compound, and pure sodium sulfide is a colorless crystalline powder. It has strong moisture absorption and is easily soluble in water. The aqueous solution shows strong alkaline reaction. Burns can occur when touching skin and hair. Therefore, sodium sulfide is commonly known as alkali sulfide.
Sodium sulfide may explode due to impact or rapid heating, and its chemical properties are unstable. In case of acid, it will release toxic hydrogen sulfide gas:
Sodium sulfide can be used in the dye industry to produce sulfur dyes. It is the raw material of sulfur blue and sulfur blue. Dyeing and printing industry is used as a dye aid for dissolving sulfur dyes. In the leather industry, it is used for hydrolyzing to remove hair from raw hides, and in the paper industry, it is used as a cooking agent for paper. It can also be used as mordant for cotton fabric dyeing in textile industry and antipyretic in pharmaceutical industry. Sodium sulfide can also be used for the treatment of conductive layer in direct electroplating. Colloidal palladium sulfide is formed by the reaction of sodium sulfide and palladium to form a good conductive layer on the non-metallic surface.