Definition of acid

1. An acid is a chemical compound that produces hydrogen ions [glossary item missing] when dissolved in water.

Strong or weak indicate the concentrations of hydrogen ions produced. Common strong acids include hydrochloric acid (HCl), nitric acid (HNO₃), and sulfuric acid (H₂SO₄). A common weak acid is acetic acid [glossary item missing] (CH₃COOH or HC₂H₃O₂); vinegar is a 3% solution of acetic acid.

Another weak acid important in geology is carbonic acid [glossary item missing] (H₂CO₃) which forms whenever atmospheric - or other - carbon dioxide (CO₂) dissolves in water (H₂).

Stronger acids will attack many minerals and can be used to help identify them. For example, acids attack carbonate minerals, such as calcite, causing carbon dioxide bubbles to be given off in an affect known as effervescence [glossary item missing].

Strong acids are dangerous and should be handled with care, only while wearing safety glasses and with plenty of water available.

2. Synonym of acidic