What does the pH measure?
Soil pH indicates how acid or basic a soil is. It is a logarithmic function of the hydrogen ion concentration [H+]: pH = -log [H+]. A pH of 6.0 is ten times more acid than a pH of 7.0; a pH of 5.0 is 100 times more acid than a pH of 7.0, and so on. A pH of 7.0 is neutral; below 7.0, the soil is acid; above 7.0, the soil is basic. For example, battery acid has a very low pH (<3.0); household ammonia is basic and has a high pH (>10.0). [Acidic < pH 7.0 > Basic].
It measures acidity or alkalinity. The scale is logarithmic, and runs from 0 to 14. A pH of 7 indicates a neutral solution, while lower pH is acidic and higher pH is alkaline. Because the scale is logarithmic, a pH of 5 is ten times more acidic than a pH of 6. What pH literally measures is the concentration of H+ ions in a solution. pH stands for the French “pouvoir hydrogène,” meaning “hydrogen potential.” pH is important for many things in biochemistry. Certain bodily fluids have a particular pH that aids their function, like highly acidic gastric acid. At the same time, the pH of the environment can have a significant effect on life, such as the harm caused by acid rain.
