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Information About Sodium Hydroxide (NaOH)

Abhay Burande Jan 27, 2019
Sodium hydroxide (NaOH), also known as caustic soda, or lye, is an important inorganic compound. Here we will take you through how it is manufactured, its characteristics, and symptoms and effects of sodium hydroxide poisoning.
Sodium hydroxide is also known as sodium hydrate, caustic soda, or lye. It is a white solid and is available in flakes, pellets, granules, and a 50% saturated solution. Since it absorbs carbon dioxide from the air, it has to be stored in an airtight container.
It can be dissolved in water accompanied by liberation of heat. It can also be dissolved in ethanol, methanol, and potassium hydroxide.
It is a very important compound for the chemical industry, especially as a strong chemical base for soaps and detergents, and as a cleaner for unclogging the drains. Before moving on to other details, let us first see some of its characteristics.

Characteristics of Caustic Soda

  • The melting point of NaOH is 318ºC and boiling point is 1390ºC.
  • It vapor pressure is 1 mm Hg at 739ºC.
  • Its specific gravity is 2.12.
  • It is incompatible with a large variety of materials like many metals, cyanides, phenols, ammonium compounds, acids, nitro compounds, and combustible organics.
  • It is highly corrosive and leads to severe burns.
  • It causes serious permanent eye damage and is very harmful if ingested.
  • It is harmful even if it comes in contact with skin contact or inhaled with dust.

Manufacturing Process

Membrane cell process

There exists a Nafion membrane to separate the cathode and anode reactions. Across this membrane, only sodium ions and a small quantity of water pass through it. A standard quality of NaOH is produced through this method. It requires very consumption of electric energy and the quantity of steam required for concentration of the caustic soda is very less.

Diaphragm cell process

In this process, a steel cathode is used. During this process, the anode area is separated from the cathode area using a permeable diaphragm that is often made of asbestos fibers. Brine is added into the anode compartment, and this flows across the diaphragm into the cathode compartment.
Chlorine ions are oxidized to produce chlorine, and water gets split into caustic soda and hydrogen at cathode. The diaphragm prevents the reaction of caustic soda and chlorine from taking place. Caustic brine in a diluted condition leaves the cell. This has to be concentrated usually to 50% and the salt should be removed.
An evaporative process is used where there are three tons of steam per ton of caustic soda. This salt is then separated from the caustic brine and is used to saturate dilute brine. The chlorine is purified by liquefaction and evaporation, hence, removing the oxygen.

Mercury cell process

It is also known as the Castner-Kellner process. A saturated brine solution is made to float on top of the cathode, which is a thin layer of mercury. Chlorine is formed at the anode, and sodium ions are reduced to sodium metal at the cathode. This forms an amalgam with mercury. The amalgam then reacts with water to form NaOH.

Symptoms of NaOH Poisoning

It may happen that you may ingest, inhale, or come in contact with NaOH accidentally. Let us see the symptoms that will help you take immediate action in such a situation.

Gastrointestinal symptoms

  • Severe abdominal pain
  • Vomiting blood
  • Diarrhea
  • Burns of the esophagus and stomach
  • Blood in the stool

Respiratory symptoms

  • Throat swelling
  • Difficulty in breathing
  • Inflammation
    of lungs
  • Sneezing

Skin symptoms

  • Burns
  • Irritation
  • Necrosis in the skin or underlying tissues

Other symptoms

  • Severe pain or burning in the nose, eyes, ears, lips, and tongue
  • Loss of vision
  • Severe pain in the throat
  • Severe change in pH ― very high or little acid in the blood that damages all the body organs
  • Hypotension (low blood pressure) raises rapidly
  • Collapse

Effects on Health

As mentioned earlier, you may be exposed to NaOH through breathing, drinking, touching, or even eye contact. It may cause mild or serious effects on health, depending upon the exposure.
  • It is very corrosive and can lead to severe burns in all tissues that are connected to it. It has a tendency to eat away any part of the body that comes in contact with it.
  • If solid or liquid sodium hydroxide are ingested, they may lead to spontaneous vomiting, chest and abdominal pain, and difficulty while swallowing.
  • Inhaling low levels of sodium hydroxide as dusts, mists, or aerosols can cause irritation of the nose, throat, or respiratory airways.
  • Corrosive injury to the mouth, esophagus, throat, and stomach is very fast and may cause hemorrhage, perforation, or narrowing of the gastrointestinal tract.
  • Inhaling high levels of NaOH can lead to swelling or spasms of the upper airway, which may lead to obstruction and loss of measurable pulse, inflammation and collection of fluid in the lungs.
  • Skin contact may lead to severe burns with deep ulcerations.
  • Eye contact may cause pain and irritation and in many cases, clouding of the eye and even blindness.
Even though sodium hydroxide is an important compound, it can prove to be quite dangerous. Therefore, make sure that you are very careful while handing it. In case of any kind of exposure to it, mild or serious, get immediate medical help. You don't want the problem to worsen, do you?