Sodium bicarbonate

Sodium bicarbonate is a white, crystalline chemical compound with the formula NaHCO3. It is a salt made of a sodium cation and a bicarbonate anion. Most people know it by common names like baking soda, bread soda, or bicarbonate of soda. In the United States, "baking soda" is the most frequent term used. In the United Kingdom, Australia, and New Zealand, people often call it "bicarbonate of soda." It has a slightly salty and alkaline taste. This taste is similar to sodium carbonate, also known as washing soda. In nature, it appears as the mineral nahcolite or as a part of the mineral trona.

One of its most famous roles is as a leavening agent in cooking. A leavening agent is a substance that makes dough or batter expand. This happens through a chemical reaction that releases carbon dioxide gas. When sodium bicarbonate meets an acid, it reacts to produce salt, water, and gas. Common kitchen acids include vinegar, citric acid, lactic acid, and cream of tartar. The gas creates bubbles that lift the batter, creating a light texture in cakes and breads.

Heat can also trigger a process called thermal decomposition. This is when heat alone causes the compound to break down. When heated above a certain temperature, sodium bicarbonate turns into sodium carbonate, water, and carbon dioxide. If a baker uses only heat without an acid, they only release half the available gas. This can also leave a bitter, soapy taste and a yellow color in the food. Because of this, many bakers use baking powder instead. Baking powder is a mixture containing about 30% bicarbonate and various acidic ingredients. These acids are activated by water, so the powder works without needing extra acid from the recipe.

Sodium bicarbonate is also a vital tool for fire safety. It can extinguish small grease or electrical fires if it is thrown over the flames. When it heats up, it undergoes an endothermic reaction. This means it absorbs heat from the fire while releasing carbon dioxide and water. The gas helps smother the fire by depriving it of oxygen. It also forms intermediates that can scavenge free radicals, which are particles that help fire spread. In grease fires, it can even create a soapy foam through a process called saponification. However, it should never be used on deep fryer fires, as the sudden gas release might cause grease to splatter.

In the medical field, this compound has several important uses. It can act as an antacid to treat heartburn by neutralizing stomach acid. In hospitals, doctors may use an intravenous solution of sodium bicarbonate to treat acidosis. This is a condition where the blood pH becomes too low. The bicarbonate helps move the blood's chemistry back to a healthy balance. It is also used in medically supervised cardiopulmonary resuscitation. Additionally, it can be used to treat certain overdoses, such as aspirin, by creating a basic environment that slows absorption. It can even be added to local anesthetics to make injections less painful.

Cleaning and industrial uses are also very common. A process called sodablasting uses sodium bicarbonate to remove paint or corrosion. This is safer for soft materials like aluminum, copper, or timber than using sand. It can also be used as a gentle scouring powder to remove rust. A solution of baking soda in warm water can even remove tarnish from silver if aluminum foil is present. During the Manhattan Project in the 1940s, a 2% solution was used to wash uranium oxides out of cotton cloth. This was important because the uranium was toxic and very difficult to remove with regular soap.

Finally, sodium bicarbonate is used in personal hygiene and agriculture. It is an ingredient in many mouthwashes because it cleans teeth and neutralizes mouth acid. It is also used in some deodorants and for nasal irrigation. In agriculture, it can be applied to leaves to prevent the growth of fungi. It is also used as a dietary supplement for sheep to help prevent bloat. Even in the home, it is a famous odor remover. A massive advertising campaign by Arm & Hammer in 1972 helped make the practice of keeping a box in the refrigerator a household standard.