Ostwald method of manufacture of HNO3 produces HNO3 of moderate concentration which is concentrated to about 68%o by mass by distillation. Further concentration to about 98% is achieved by dehydration with:

Ostwald method of manufacture of HNO3 produces HNO3 of moderate concentration which is concentrated to about 68%o by mass by distillation. Further concentration to about 98% is achieved by dehydration with concentrated H2SO4