Sodium

Brief overview

Sodium metal (Na), also known as Natrium, is a highly flammable, light-weight silver solid chemical. As it releases hydrogen, it will ignite spontaneously when it is in contact with water or moist air. When reacted with water, it produces sodium hydroxide and hydrogen. When metallic sodium is exposed to air, its color changes from silver to opaque gray because it forms a sodium oxide coating. Sodium metal is odorless and has a low melting point of about 97.5°C. Sodium metals do not exist as pure solids because they are too reactive. Sodium can be found in nature, such as the crust and sea water. It usually contains salt (sodium chloride) or sodium hydroxide.

Sodium does not react with nitrogen, but it reacts with ammonia to produce sodium amide. It also does not react with paraffinic hydrocarbons and hardly reacts with carbon. The reaction between sodium and alcohol is also explosive, but it occurs at a slower rate than sodium and water. When it reacts with hydrogen, it forms sodium hydride. The reaction occurs at temperatures above 200°C. Sodium also reacts with several halides and the reaction is divided into two steps.

Manufacturing Process

Commercially there are two method of manufacturing sodium metal, which is Castner Process and Down Cell.

Castner Process

One of the most common methods of producing sodium metal is The Castner Process. This process occurs by electrolysis reaction of molten NaOH (sodium hydroxide) at temperature 330oC. This method was first introduced by Hamilton Castner in 1888. In this process, cathode and anode are made from nickel or iron. When sodium hydroxide is electrolyzed, sodium metal will form at cathode. Reaction that occurs in cathode and anode is shown below:

Cathode Reaction: 2Na⁺ + 2e^- → 2Na

Anode Reaction: 2OH^- → ½ O₂ + H₂O + 2e^-

Hydrogen gas also formed from this reaction as by-product. As the result, the presence of hydrogen gas decreasing the efficiency of this process.

Downs Cell

This manufacturing method is an electrolyte reaction using molten sodium chloride. Down cell uses an iron cathode and a carbon anode. In this process, another compound is added such as calcium chloride and sodium fluoride to lower the melting point. Products from this reaction are sodium metal and chlorine gas. Sodium is formed at cathode and chlorine at anode. The reaction in anode and cathode is shown below:

Cathode reaction: 2Na⁺ + 2e^- → 2Na

Anode reaction: 2Cl^- → Cl₂ + 2e^-

The major product from this process is sodium metal. Downs Cell is more efficient than the Castner Process.

Intermediate Chemical

Sodium metal is largely use in chemical industry for producing various compounds. It improved the structure of certain alloys, smoothen the surface of metal, and purify molten metal. Sodium and potassium alloys can be used as heat transfer agent, dry solvents, and chemical reducing agent. Sodium and mercury alloy (amalgam) is useful in fluorescent lamp that consumes less electricity and one of the most efficient energy light sources.

Pharmaceutical Industry
Sodium also used in pharmaceutical for several drug productions. Reacting sodium metal with alcohol produces the starting material for drugs production. Sodium salt, such as sodium bromide can be used to treat seizures and headache. Diclofenac sodium is used to treat pain and reduce inflammation that accompanies rheumatoid arthritis and osteoarthritis. People who suffer from muscle injuries also can use sodium, in the form of naproxen sodium, with the right dosage.

Nuclear Power Industry
Sodium is used in nuclear power plant as a coolant. Nuclear fission reaction that occurs in the core of a nuclear reactor produces large amount of heat energy. Sodium in the form of liquid is stored into pipes that surround the core of reactor. The heat that produced from the reactor then absorbed by the sodium liquid and stored to another place. The sodium that has absorbed the heat is wrapped around pipes filled with water to create steam. The steam is used to operating some device.

Rubber Industry

Sodium is used as a catalyst for the manufacture of elastomers. Real rubber made from collected rubber sap is expensive and therefore produces synthetic rubber. It is common to use small-molecule synthetic rubber raw materials that constantly react with themselves to form polymers. Sodium metal is added to the process to accelerate the reaction.

Other Applications

Sodium metal is used to make tetraethyl lead (PbEt4), but it has not been used in many countries due to pollution problems. Another use of sodium metal is to prepare metallic titanium from TiCl4. Sodium compounds such as sodium bicarbonate, sodium chloride, sodium carbonate and sodium hydroxide can be used in various industries, including the paper industry, the glass manufacturing industry, the soap industry, the textile industry, and the petroleum industry.