An acid is a solution with a pH <7. The pH of Lemon juice is around 2.


A base is also known as an alkali. A solution with a pH >7. Bleach has a pH around 12.


Has a scale of zero to 14. pH of <  7 is an acid 7 is neutral pH > 7 is a base.    

pH meter

An electronic instrument used to measure the pH (acidity or alkalinity) of a substance.


The adjusting of a solution’s pH through the addition of an acid or a base. Performed by automatic titrators or manually with the use of a pH meter.