Sodium

Sodium (NA 23). Although not occuring naturally in a free state, this metal is, in combination, one of the most abundant of the elements. As common salt it occurs largely dissolved in seawater, salt lakes, and in saline deposits; it is found as nitrate in deposits on the soils in Chili, etc.; and occurs also naturally as carbonate, phosphate, and borate. The silicate exists in many rocks and minerals, being an important constituent of the micas. It is also found in many plants, particularly in marine vegetation. The metal itself was first prepared by Sir Humphry Davy, who obtained it in 1807 by the electrolysis of the fused hydrate. It is now manufactured by strongly heating a mixture of carbonate of soda and charcoal in iron retorts, recent years having brought great improvements in the details of the process. It is it silver-white metal, soft enough to be easily cut by a knife. It is a little lighter than water, having a specific gravity of .97. It melts at 97.6° C., and may he volatilised in absence of air, the vapour being of a blue colour. If exposed to the air, the surface of the metal immediately tarnishes and becomes covered with a coating of the hydrate. If placed upon water, it immediately melts into a small ball, which floats upon the liquid, decomposing it with the evolution of hydrogen -

2H₂O + Na₂ = 2NaOH + H₂

The substance NaOH which is formed is known as sodium hydrate or caustic soda and remains dissolved in sea water, to which it imparts powerful alkaline properties. It is a white solid which is prepared usually by the action or milk of lime upon a boiling solution or sodium carbonate. It is a strong caustic and alkali, and is extensively used for teohnica1, chemical, and manufacturing purposes. Sodium forms two oxides, which are, however, unimportant. Among its salts, however, are many important compounds. The carbonate is known under the name of soda (q.v.), and the nitrate forms the compound Chili saltpetre (q.v.). The silicate is soluble in water, and is known as soluble glass, being employed for fire-proofing, etc. The phosphate is important chemically, and the borate [BORAX] has many applications. The soaps are also but sodium salts of certain organic acid, while common salt is the chloride of sodium, NaCl. The metal itself is used in the preparation of other elements, notably aluminum, the recent falling in the price of this metal being chiefly due to the improvements in the processes of obtaining sodium.