Delphinidin

The concentration of H+ ions present is used to define degrees of acidity or alkalinity on a specific scale, called the pH scale. The scale ranges from 0 to 14, with each unit representing a tenfold change in H+ concentration. Pure water has a pH of 7—the point on the scale where the number of H+ and OH– ions is exactly the same, or the neutral point.1 The lower a number is below 7, the higher the degree of acidity; conversely, the higher a number is above 7, the higher the degree of alkalinity.
Vinegar, for example, has a pH of 3, tomato juice has a pH of 4.3, and egg white has a pH of 8. Precipitation with a pH of less than 4.5 is now commonly referred to as acid rain (acid deposition). Acid rain is associated with industrial emissions, and appears to be causing damage to vegetation, soil organisms, and buildings in some parts of the world, including North America.

When an acid and a base are mixed, the H+ ions of the acid bond with the OH– ions of the base, forming water (H2O). The remaining ions bond together, forming a salt. If hydrochloric acid (HCl) is mixed with a base—for example, sodium hydroxide (NaOH)—water (H2O) and sodium chloride (NaCl), a salt, are formed.