Sodium sulphate anhydrous is a white crystalline compound with the formula, Na2SO4. It also exists as a decahydrate, Na2SO4.10H2O, called Glauber’s salt. It is a stable compound and soluble in water.
Sodium sulphate anhydrous is available in the form of thenardite ore. It is commercially prepared from two processes, Mannheim and Hargreaves process. The anhydrous form is obtained from hydrate form by gentle heating.
Mannheim process: It is the process of preparing hydrochloric acid from sodium chloride and sulphuric acid. Sodium sulphate is produced as a by-product
NaCl + H2SO4 à Na2SO4 + HCl
Hargreaves Process: In this process, sodium chloride reacts with sulphur dioxide to form sodium sulphate.
4NaCl + 2SO2 + O2 + 2H2O à 2Na2SO4 + 4HCl
Another process to produce the sulphate is from rayon production. The excess sulphuric acid produced in the manufacture is neutralised using sodium hydroxide