Question

What is `"sulfurous acid"`?

Answer 1

I am not sure what you are asking.

Explanation:

Sulfurous acid is supplied as an aqueous solution labelled `H_2SO_3`. It has smell that is not entirely unpleasant; I tend to like it because it has a clean, medicinal smell. It could equally be represented as `O_2S*H_2O`, i.e. the water adduct of `SO_2`. Both `SO_2` and `SO_3` have some water solubility, and are the acid anhydrides of sulfurous and sulfuric acid.