The pH scale is a mathematical creation. It is a negative logarithm of the number of hydrogen ions (H+) in a solution, expressed as a number between 1 and 14, without units.

The pH Scale
 1  7 14
 The lower the pH, the more acid the substance.  Pure water has a neutral pH of 7  The higher the pH, the more alkaline the substance
An acid is a substance that, when dissolved in water, produces a net of hydrogen (H+) ions.    An alkali is a substance that, when dissolved in water, yields a net of hydroxide (OH-) ions. 

Instant Feedback:

Low pH is:

If you have one H+ and one OH- together, you have water.

(H+) + (OH-) = H2O

Points to remember:

  1. The pH scale goes from 1 to 14.
  2. Low pH is acid.
  3. High pH is alkaline.
  4. pH 7 is Neutral


Click here to enter the Tulane Univ. School of Medicine, Dept. of Anesthesia pH tutorial. Click on "Understand pH"