Sodium Hydroxide, also known as caustic soda, is a heavy chemical in that it is used and needed in large amounts in the industries. It is a soluble base or alkali  manufactured by the electrolysis of concentrated brine, NaCl.In the laboratory, sodium hydroxide may be prepared by the action of sodium trioxocarbonate (IV) on calcium hydroxide:
Na₂CO_3(aq) + Ca(OH)_2(s) -----------> CaCO_3(s) + 2NaOH(aq)

Properties of NaOH

1. It is a white crystalline and deliquescent solid, often found as pellets;
2. It has melting point range of between 315^oC and 325^oC;
3. It reacts with dilute acids to form salt and water only. This reaction is called neutralization reaction:
   NaOH_(aq) + HCl_(aq)------->NaCl_(aq) + H₂O_(l)
4. Ammonia gas,NH₃ is formed, when an ammonium salt reacts with the solution of sodium hydroxide:
   NaOH_(aq) + NH₄Cl_(s)------->NaCl_(aq) + H₂O_(l) + NH_3(g)
5. Some metals like aluminum and zinc easily dissolve in sodium hydroxide to form sodium aluminate (III) and sodium zincate (II) respectively while hydrogen gas is given off;
   2Al_(s) + 6H₂O_(l) + 2NaOH_(aq)--->2NaAl(OH)_4(aq) + 3H_2(g)
   Zn_(s) + 2H₂O_(l) +2NaOH_(aq) ---------->Na₂Zn(OH)_4(aq) + H_2(g)
6. Sodium hydroxide reacts with several common non-metals to form the corresponding sodium salts of the non-metals;
7. Sodium hydroxide is a precipitating agent. This property is very useful in the identification of metal cations in the laboratory because of the color of the hydroxides formed as well as their solubility in the excess NaOH.
8. Sodium hydroxide precipitates them as insoluble hydroxides which are gelatinous as in those of zinc, aluminum and sometimes lead or uniform as in calcium and magnesium or barium.
   2NaOH_(aq) + Pb(NO₃)_2(aq)--->Pb(OH)_2(s) + 2NaNO_3(aq)
   Zn(OH)_2(aq) + 2NaOH_(aq)--------> Na₂Zn(OH)_4(aq)
9. The hydroxides of zinc, aluminum, tin and lead are amphoteric in nature and so would dissolve again in the excess of the sodium hydroxide to form complex salts. This will be a topic for another day.
10. Concentrated NaOH attacks glass and this explains why glass stoppers are never used to cover the reagent bottles containing the hydroxide. The stoppers will become sealed and cause such bottles extremely difficult to open.

Uses of Sodium Hydroxide

1. Sodium hydroxide is usually employed in the laboratories as strong alkali and as an analytical and precipitating reagent as discussed earlier.
2. It is also used for absorbing carbon(IV)oxide gas.
3. In the industries, NaOH is used for the following:

1. Purification of bauxite in preparedness for the extraction of aluminum;
2. Bleaching of cotton textiles;
3. Making of soap, artificial silk (rayon)and paper

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