Acids are familiar to us because of their power as corrosive agents and solvents, bringing into solution compounds that are insoluble in water alone

Strong acids will attack many metals, converting them to soluble ions and liberating bubbles of hydrogen gas in the process.

Acids also will dissolve carbonates such as limestone, and certain other minerals and inorganic compounds. The weaker acids that are safe to taste, such as citric acid in lemons and acetic acid in vinegar, have a characteristic mouth puckering sharp taste that we immediately recognize and designate as "acid".

Bases also are useful for dissolving water-insoluble substances, especially oils, greases, and other organic compounds. Sodium hydroxide, for example, will attack the oils of the skin and turn them into soap, which is why solutions of household lye feel slippery to the touch.

We have seen previously that there are many substances, amphoteric oxides among them, that are insoluble in plain water but are dissolved either by an acid or a base, or both.