The manufacture of glass is one of the most important uses of sodium carbonate. When it is combined with silica (SiO2) and calcium carbonate (CaCO3) and heated to very high temperatures, then cooled very rapidly, glass is produced. This type of glass is known as soda lime glass.
Soda ash also is used to clean the air and soften water.
Manufacture of Caustic Soda and dyestuffs
Metallurgy (processing of steel and extraction of iron etc),
Flat glass, sanitary pottery
national defence (TNT manufacturing, 60% gelatin-type dynamite ) and some other aspects, such as rock oil refining, paper manufacturing, paint, salt refining, softening of hard water, soap, medicine, food and so on.