|Atomic mass||22.9898 amu|
In 1807, sodium metal was successfully isolated by inserting electrodes into a bath of molten sodium hydroxide (NaOH). Molten sodium metal was found forming around the cathode. This process is called electrolysis.
Sodium is a very soft, silvery-white metal. It is so soft that it can be easily cut with a knife. Compounds of sodium are very common, but the metal itself cannot be found in nature in its pure form. Pure sodium metal has virtually no practical application since it reacts vigourously under normal environmental conditions. It isso reactive that the pure metal has to be stored in containers filled with a non-reactive liquid such as kerosene.
Today sodium is produced commercially by the same procedure used for isolating the first samples of the pure metal nearly two centuries ago. The procedure is based on the electrolysis of molten sodium chloride (NaCl), table salt. Electrolyzing molten sodium chloride produces chlorine gas at the anode and sodium metal at the cathode. The commercial electrolytic process is called the Downs process.
There are many different sodium compounds that are useful. Listed below are some common ones:
- sodium bromide, NaBr. This compound is used in medicine and photography.
- sodium chlorate, NaClO3</sub. This is a powerful oxidizing agent. It is used in explosives, in matches, as a weed killer, and in the textile industry.
- sodium chloride, NaCl. This is also known as table salt.
- sodium hydroxide, NaOH. This compound is used in the chemical industry. The only common household application is as a drain cleaner.
- sodium bicarbonate, NaHCO3. This is also known as baking soda. It is used as a leavening in bakery products, in stomach antacids, in effervescent beverages, and as a fire-extinguishing agent.
- sodium carbonate, NaCO3. This compound is called "washing soda" because of its use in water softening. It is also commonly used as a cleaning agent and bleach.
- sodium hexametaphosphate, Na2[Na4(PO3)6]. This is also known as Calgon. Calcium ions in water can be prevented from precipitating with soap or forming boiler scale by tying them up in soluble complex ions with the use of Calgon.
- sodium cyanide, NaCN. This is used in the steel industry. Large amounts of this highly toxic compound are used each year to case-harden steel.
- sodium nitrate, NaNO3. This is a common component in fertilizers and explosives.
- sodium sulfate, NaSO4. Depending upon its water content, they have different names:
- anhydrous sodium sulfate, NaSO4, is free of water. It is used as a drying agent in chemistry laboratories.
- sodium sulfate decahydrate, NaSO4.10H2O. This is known as Glauber's salt. It is used in the manufacture of glass and as a purgative in medicine.
- sodium thiosulfate, Na2S2O3. This compound is used in photography as "hypo".