Friday, November 14, 2008

What is Sodium hydroxide?

Sodium hydroxide (NaOH), also known as lye, caustic soda and as sodium hydrate, is a caustic metallic base. Sodium hydroxide forms a strong alkaline solution when dissolved in a solvent such as water. It is used in many industries, mostly as a strong chemical base in the manufacture of pulp and paper, textiles, drinking water, soaps and detergents and as a drain cleaner. Worldwide production in 1998 was around 45 million tonnes. Sodium hydroxide is the most used base in chemical laboratories.

Pure sodium hydroxide is a white solid; available in pellets, flakes, granules and as a 50% saturated solution. It is deliquescent and readily absorbs carbon dioxide from the air, so it should be stored in an airtight container. It is very soluble in water with liberation of heat. It also dissolves in ethanol and methanol, though it exhibits lower solubility in these solvents than potassium hydroxide. It is insoluble in ether and other non-polar solvents. A sodium hydroxide solution will leave a yellow stain on fabric and paper.

Sodium hydroxide uses (Wikipedia):

General Application

Sodium hydroxide is the principal strong base used in the chemical industry. In bulk it is most often handled as an aqueous solution, since solutions are cheaper and easier to handle. It is used to drive chemical reactions and also for the neutralization of acidic materials. It can be used also as a neutralizing agent in petroleum refining. It is sometimes used as a cleaner.

A solution of sodium hydroxide in water was traditionally used as the most common paint stripper on wooden objects. Due to its caustic nature and the fact that it can damage the wood surface raising the grain and staining the color, its use has become less common.

Other paint stripper formula:
  1. General Purpose Stripper - DCM Free
  2. Methylene Chloride-Free Paint Stripper
  3. General Purpose Stripper
  4. General Purpose Stripper - Dibasic Ester Based
  5. Solvent Based Paint Stripper
Soap production

Sodium hydroxide was traditionally used in soap making (cold process soap, saponification). The Arabs began producing soap in this way in the 7th century, and the same basic process is used today.

For the manufacture of biodiesel, sodium hydroxide is used as a catalyst for the transesterification of methanol and triglycerides. This only works with anhydrous sodium hydroxide, because combined with water the fat would turn into soap, which would be tainted with methanol. It is used more often than potassium hydroxide because it is cheaper and a smaller quantity is needed.

Domestic uses

Sodium hydroxide is used in the home as a drain cleaning agent for clearing clogged drains. It is distributed as a dry crystal or as a thick liquid gel. The chemical mechanism employed is the conversion of grease to a form of soap. Soap is water-soluble, and can be dissolved by flushing with water. Sodium hydroxide also decomposes complex molecules such as the protein that composes hair. Such drain cleaners (and their acidic versions) are highly caustic and should be handled with care.
Sodium hydroxide has been used as a relaxer to straighten hair. However, because of the high incidence and intensity of chemical burns, chemical relaxer manufacturers have now switched to other alkaline chemicals, although sodium hydroxide relaxers are still available, used mostly by professionals.

Cleansing agent

Sodium hydroxide is frequently used as a cleaner in breweries, where it is simply called "caustic". It is added to water, heated, and then used to clean the large stainless steel tanks where beer is brewed, fermented, and stored. It can dissolve oils and protein-based deposits. A sodium hydroxide soak solution is used as a powerful degreaser on stainless and glass bakeware. It also the most common ingredient in oven cleaners.

Lye is created out of a chemical reaction between soda, known as sodium carbonate, and calcium hydroxide, or lime. In raw form, it's made into solid flakes, chips, or grains. Chemical suppliers provide lye to manufacturers to make a wide variety of products, such as fabric, paper, personal soap, laundry detergent, pool-cleaning supplies, metal polishers, and drain de-cloggers. Since households utilize so many poisonous products, they must take care to keep cleaners out of the reach of children and only use them as directed. For instance, carefully follow the directions to clean a sterling silver gravy boat with lye-based polish, because even the fumes can be dangerous. Never use products like drain de-clogger or paint stripper without enough air circulation.

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