What is sodium?
It is a highly reactive metal which a chemical symbol “Na” it placed in 3rd row and 1st column of the periodic table in a group of alkali metals, It is identified with its atomic number 11 and atomic mass 22.989.
Where do I find it?
Naturally, it is present in common salt called sodium chloride ‘NaCl’ , in chile saltpetre NaNO3, cryolite(Na3AlF6) and sodium sesqui carbonate.
Sodium metal extraction methods:
To extract sodium as it is we have two famous methods
- Castner Process: Principle method is Electrolysis of sodium hydroxide
- Down’s process: Based on Electrolysis of sodium chloride
By the application of electrolysis technique, sodium hydroxide is fused at a temperature of 318 oC so that at the cathode electrode sodium get deposited and liberating oxygen at anode electrode. Steps of the sodium metal extraction by Castner process:
- NaOH ↔ Na+ + OH– , this is fused sodium hydroxide reaction producing individual ions
- When the electrical supplying is given sodium ion move toward Na++ e– → Na
- At anode water and oxygen are evolved due to decomposing of OH- as per the reaction, 4OH– →2H2O +O2 +4e–
Above reaction are carried continuously producing sodium collected at receiver, oxygen and hydrogen. Some of the water is evaporated or decomposed to hydrogen and oxygen.
The electrolytic model explains the process of operation which operates at 318-330oC by using gas burners. Negative supply is given to solid NaOH filled with iron support and positive to the Nickel anodes the whole set up is fitted in the iron pot. The approximate dimension of the iron tank range about 1.5 ft wide and 2 ft high with a capacity of 480 kg of fused NaOH. Nickel gauze separates cathode and anode electrodes and prevents the molten sodium formed at the cathode to oxygen liberated at the anode.
Gas burners are used for the startup to raise the temperature to 315oC as the on the run the temperature is maintained by the reaction between electrode maintain the temperature. Sodium metal float to the surface collected in receiver provided with mantle at the top at the lid and seal from the atmosphere to prevent contact with oxygen. The molten sodium is removed as on when it reaches the level. A perfect seal is maintained with the iron pot and the lid with asbestos rings.
Limitation: sodium is soluble in sodium hydroxide as the temperature rises above 315oC and separation become inflexible.
Properties of sodium metal:
- Melting point: 97.5
- Boiling point: 883
- Sp gravity: 0.97 gm/cc
- Conduction: good conductor of electricity
- Appearance: silver white
- Density compared with water: lighter than water
- Solid sodium can be cut with a knife because it is soft.
- Highly reactive
- Burns with oxygen forming into sodium monoxide and sodium peroxide. 4Na + O2 →2 Na2O
- Liberate hydrogen when reacted with Hydrochloric acid. 2Na +2HCl → 2NaCl +H2
- It replaces hydrogen due to high electropositivity. 2Na + 2HNO3 →2NaNO3 +H2
- When exposed to open surrounding it reacts with moisture forming Na2O and to NaOH finally to Na2CO3.
- 2Na + O2 → Na2O2
- Na2O +H2O→ 2NaOH
- 2NaOH + CO2 → Na2CO3 +H2O
Sodium metal Uses:
It is a starting material for production and manufacturing of highly valuable chemical products like sodium hydroxide, NaCN, sodamide, dyes, perfumes, artificial rubber etc. It takes can be used as reducing agent in the form of sodium amalgam, as a detecting element of nitrogen, sulphur and halogens, deals in the extraction process of boron and silicon.