The pH scale is a logarithmic scale that measures the amount of hydrogen ions versus the amount of hydroxyl ions found in a substance. The scale runs from zero to 14, with 7 being the neutral figure. Substances with a value of 0 to 6 are considered acidic, containing more hydrogen ions than hydroxyl ions, while substances with values ranging from 8 to 14 are considered basic with more hydroxyl ions than hydrogen ions.
The number 7 on the pH scale is based on the hydrogen and hydroxyl content of pure water. In pure water, there is an equal number of each type of ion, so the solution is considered neutral. In terms of hydrogen ions, referred to as H+, neutral is equal to 1. Each number on the pH scale is 10 times more acidic or basic than the previous number. For instance, a solution with a pH of 8 is 10 times more basic than a solution with a pH of 7, so the H+ count is actually 0.1, and a pH of 9 is 10 times more basic than a pH of 8, so the H+ count is .01.
Acidic foods are characterized by their sour taste, and even get their name because of that characteristic. The word "acid" is derived from the Latin word "acere" which means "sour." Some of the more well-known acidic substances include lemons, vinegar, tomatoes, coffee and, of course, sulfuric and hydrochloric acid. The most acidic substances on the pH scale have a hydrogen concentration of 10 million hydrogen ions when compared to pure water. Mildly acidic solutions are found close to 7 on the pH scale, while highly acidic solutions are found close to zero.
Basic substances are categorized by their bitter taste and slippery feel. Also known as alkalies, thanks to 17th century chemist Robert Boyle, some of the more well-known bases include ammonia, baking soda, soap and drain cleaner. The strongest of basic substances on the pH scale have a hydrogen concentration of 0.0000001 hydrogen ions when compared to pure water. Mildly basic solutions are found close to 7 on the pH scale while highly basic solutions are found close to 14.