Products
Pure sodium hydroxide is available as open goods in pharmacies and drugstores. Sodium hydroxide is also available in solution form.
Structure and properties
Sodium hydroxide (NaOH, Mr = 39.9971 g/mol) exists as a white, crystalline, and odorless mass in the form of cookies, beads, rods, or plates. It is deliquescent and rapidly adsorbs carbon dioxide and water from the air. Sodium hydroxide is very soluble in water. It should be stored tightly closed, in a non-metallic container. Aqueous solutions are called sodium hydroxide solutions and have a soapy feel.
Effects
Sodium hydroxide is a strong and corrosive base with a pKb of -0.56. The effects are due to the release of the hydroxide ions (OH–) in water. As a detergent, it is effective against fats, oils and proteins, among others, because it hydrolyzes their ester or amide bonds. Acids are neutralized by sodium hydroxide:
- NaOH (sodium hydroxide) + HCl (hydrochloric acid) NaCl (sodium chloride) + H2O (water)
Dosage
Caution: when dissolving the substance in water, a lot of heat is released (exothermic). When preparing solutions, the water should be measured first and then add the sodium hydroxide.
Fields of application
The following list shows a small selection of the areas of application:
- For the production of soaps (ester hydrolysis).
- As a reagent.
- To adjust the pH, as an auxiliary (acidity regulator).
- For drain cleaning, as a cleaning agent, for example, for the oven (finished products).
- For the preparation of lye pastries, e.g. lye rolls, lye pretzels and lye peaks.
- As a food additive.
- For chemical syntheses.
- Numerous industrial applications.
Due to the hazardous nature of the substance, the far less toxic sodium bicarbonate (sodium hydrogen carbonate) can also be used for lye pastries.
Precautions
Sodium hydroxide has strong corrosive properties and must therefore be handled with care. It should not be touched, drunk, inhaled or ingested directly. The risks depend on the concentration. Sodium hydroxide and its solutions can cause severe burns, chemical burns, ulceration and necrosis of the skin, mucous membrane and eyes. Therefore, gloves, safety goggles or face shield, respirator and suitable clothing should be worn during handling. In case of accidental contact with the eyes or skin, rinse with water for a sufficiently long time and then contact a doctor. Inhalation and ingestion are also acutely harmful. Sodium hydroxide must be kept out of reach of children. It can have harmful effects on the environment, depending on its buffering capacity. However, small amounts rapidly degrade to harmless metabolites and no bioaccumulation occurs. Full precautions can be found in the Material Safety Data Sheet.