The chemical formula for sodium bicarbonate, also known as baking soda, is NaHCO3. Sodium bicarbonate is a salt formed through the reaction of a sodium-containing base, such as NaOH, and carbonic acid, written as H2CO3 or OC(OH)2. In carbonic acid, which is formed when carbon dioxide dissolves in water, the carbon atom is attached to three oxygen atoms, and two of the three oxygens also have hydrogen atoms attached.
When NaOH and OC(OH)2 react, the OH-group (or hydroxyl ion) detaches a hydrogen ion, H+, from the OC(OH)2 to form water, leaving a negatively charged bicarbonate ion, HCO3-. Bonds between positively positively-charged cations, such as Na+, and negatively charged anions, such as HCO3-, are known as ionic bonds.
The bonds within the bicarbonate anion are called covalent bonds and involve the sharing of electrons. The bond between the carbon atom and one of the oxygens is called a double bond (because the carbon and the oxygen have both sigma and pi bonds between them), whereas the bonds between the carbon and the other two oxygens are single bonds. The bond between the oxygen and hydrogen atoms is also a covalent bond.
Sodium bicarbonate is available in food, pharmaceutical and industrial grades. All food-grade sodium bicarbonate is required to meet United States Pharmacopoeia and Food Chemicals Codex standards for purity. Pharmaceutical-grade sodium bicarbonate has to meet Food and Drug Administration standards for purity and has to be produced in an FDA-certified facility. Industrial grades are subject to less-stringent purity standards than food grades.
Food grade sodium bicarbonate is used both in animal feed and in cooking. Sodium bicarbonate plays a role in dairy operations as a rumen buffer. Sodium bicarbonate is used in turkey and broiler chicken diets as a source of sodium and in the diets of laying hens to improve eggshell quality for laying hens. In baking, sodium bicarbonate is a leavening agent---when sodium bicarbonate reacts with other ingredients, carbon dioxide (a gas) is produced, causing the baked good to rise.
Sodium bicarbonate used for medical purposes is in the form of a 5 percent solution for injection. It is used in the process of hemodialysis for patients with kidney failure and to treat patients with metabolic acidosis (an imbalance in the pH of the blood) because of kidney failure, severe dehydration or diabetes. It is also used to treat barbiturate overdoses and poisoning by methyl alcohol and salicylates.
Major industrial uses of sodium bicarbonate are in pool chemicals and in water treatment systems. It is also used as an environmentally friendly substitute for sand in sandblasting and as a source of carbon dioxide in fire extinguishers, although these extinguishers are no longer commonly used.