How is trioxonitrate (V) acid prepared in the laboratory?

Concentrated sulfuric acid ($\text{H}_2\text{SO}_4$) is reacted with a nitrate salt, typically potassium nitrate ($\text{KNO}_3$) or sodium nitrate ($\text{NaNO}_3$).

The nitrate salt is heated with concentrated sulfuric acid in an all-glass apparatus. The nitric acid produced is volatile and distills off as a gas, which is then condensed in a cooled receiver to form liquid nitric acid.

The reaction between potassium nitrate and concentrated sulfuric acid is:

The nitric acid gas ($\text{HNO}_3(g)$) is then condensed to form liquid $\text{HNO}_3(l)$.

The laboratory preparation of trioxonitrate (V) acid involves heating a nitrate salt (e.g., potassium nitrate) with concentrated sulfuric acid. The nitric acid produced is collected by distillation.