The soda is a corrosive chemical solution and transparent.

The hydroxide ion is a strong base.

Manufacturing Techniques

History

In the ancient times , people used soda plant. Soda, then the word for " soda , came from the ashes obtained by combustion of plant halophytes such as Salicornia or Welded. Caustic soda is then obtained by causticizing (see below). In 1791 , the chemist Nicolas Leblanc invented a method to obtain the sodium carbonate from seawater, a process that will be superseded by the Solvay process in 1861 (by Ernest Solvay ). These methods can reduce the cost price of soda. In the late nineteenth ^century the advent of electricity allows the direct production of caustic soda by electrolysis of a solution of sodium chloride. Today 99% of the original soda is produced electrochemically.

sodium hydroxide pellets.

Electrolysis of brine (salt saturated water)

Soda ash is obtained by electrolysis of chloride sodium NaCl.

The soda is obtained for the moment mainly by electrolysis with mercury cathode (anode titanium cathode: mercury). This operation produces the same time the chlorine , caustic soda and the hydrogen. But mercury is a heavy metal harmful bioaccumulation and very low dose, even more when transformed into mono-or di- methyl mercury by bacteria. It is volatile and non-degradable and easily pass the barrier of the lungs, making it one of the major pollutants of the environment, increasing in all seas. That's why this method will disappear by 2020 and is being replaced by membrane electrolysis ^{Beginning of sodium carbonate}

This technique was once used. It is still used in North America where natural deposits of sodium carbonate. It is an addition of lime (raw) with sodium carbonate. We talk causticising or caustic. The reaction is written:
Na ₂ CO ₃ + Ca (OH) ₂ CaCO ₃ +2 NaOH

Lime Manufacture:

By calcination of limestone (CaCO ₃₎ to 900 C is obtained from the lime (calcium oxide CaO) and low release of carbon dioxide (CO _2):

The reaction is accompanied by a mass loss of about 45%, corresponding to the loss of carbon dioxide by chemical formulation follows:

CaCO ₃ CaO + CO ₂

The transformation of quicklime into hydrated lime, is made by adding water (H ₂ O). This operation produces the extinction of calcium hydroxide Ca (OH) ₂ with evolution of considerable heat;

Uses

Solubility curve of sodium hydroxide in water.

• Sodium hydroxide is used in large quantities by several industries, mainly as a base especially for the manufacture of pulp and paper , chemicals and plastics, soap and detergent products in general, certain textiles , artificial l Aluminium (processing bauxite ). Soda is used to regulate the pH and regenerate ion exchange resins for water treatment stations.
• In food it serves to clean the facilities (circuit, bottles), modify starch, chemical peeling, etc.. It is also a food additive (E524 ) is used as acidity regulator and is used in a wide range of products .
• The unblocking chemicals are often based on sodium hydroxide.
• World production in 1998 was about 45 million tonnes. Sodium hydroxide is the base most commonly used in laboratories.
• The soda can be used to store solar energy in chemical form. Indeed, the reaction between soda and water is highly exothermic. Once diluted soda, just use direct solar energy to evaporate water and return to the initial state.
• Soda ash is also used as a reagent for chemistry tests. Indeed, in the presence of certain cations , metal soda precipitate a certain color.

• Soda ash is used in some hair relaxers, but tends to be abandoned in modern cosmetics.

Health effects

Sodium hydroxide reacts violently with water in appreciable quantities only, and may cause dangerous splashing. When mixed with water, the temperature of the mixture increases until it reaches a temperature close to that of boiling water, 100 C. Caustic soda is irritating and corrosive to the skin , the eyes , respiratory and digestive tracts. It must be handled with gloves, eye protection and respiratory protection. In case of skin contact, rinse thoroughly with water and see a doctor.

In case of accidental ingestion, do not induce vomiting because of the risk of burning double (round trip). We must call the emergency control center or fish as soon as possible. Boire acids (lemon juice, oranges, kiwis etc ...) would counteract the effect of the base on the walls of the stomach and especially drink plenty (+ one liter per quarter hour) water as cold as possible to minimize corrosion and elevated temperature too brutal walls of the stomach, it will also result in limit corrosion of the walls of the esophagus

Environmental effects

Caustic soda increases the pH of streams, representing a potential threat to aquatic fauna and flora.

Caustic soda should not be confused with sodium bicarbonate , or with sodium carbonate.

Caustic soda seeps into the ground, can affect agriculture as the environment of plants, minerals and animals near and far (river, groundwater).

References