The measure of acidity or alkalinity in a liquid is known as pH, which stands for the “potential of hydrogen.” This scale ranges from 0 to 14, indicating the concentration of hydrogen ions in a solution. Pure water has a pH of 7.0, which is considered neutral. Values below seven are acidic, and the closer the number gets to zero, the stronger the acid is. Conversely, values above seven are alkaline, or basic. Because the scale is logarithmic, a change of one whole number represents a tenfold difference in acidity. Soda pop is widely known as a highly acidic beverage, placing it far down the acidic end of this scale.
Defining the Acidity: Typical pH Values of Soda Pop
Most commercial soda pops fall into a highly acidic pH range, typically measuring between 2.5 and 4.0. Some colas can have a pH as low as 2.37, making them over 10,000 times more acidic than neutral water. This range is comparable to the acidity levels found in lemon juice (around pH 2.25) or vinegar (pH 2.4 to 3.4). The specific type of soda determines where it falls within this narrow band. For instance, colas and lemon-lime drinks often have the lowest values, while some root beers have pH levels closer to 4.1 or 4.7.
The Chemical Causes of Low pH
The primary reason for soda pop’s low pH is the deliberate addition of various food-grade acids, which enhance flavor and act as preservatives. The most significant contributor in many popular cola beverages is phosphoric acid. This acidulant provides a sharp, tart taste and helps inhibit the growth of mold and bacteria, allowing for a longer shelf life. Phosphoric acid dissociates in the drink to release a high concentration of hydrogen ions, directly causing the extremely low pH values seen in colas.
Another common source of acidity is carbonic acid, which forms when carbon dioxide gas is dissolved into the water during carbonation. This process is responsible for the characteristic “fizz” of soda. While carbonic acid is a weaker acid than phosphoric acid, it still releases hydrogen ions into the solution, contributing to the initial drop in pH. Furthermore, fruit-flavored and citrus sodas rely heavily on citric acid and sometimes malic acid to provide their tangy taste. Citric acid is a flavor enhancer that can lower the pH into the 3.0 to 4.0 range.
Acidity’s Impact on Dental Health
The extremely low pH of soda pop directly causes dental erosion, which is the irreversible loss of tooth structure from chemical dissolution. Tooth enamel, the hardest substance in the human body, is primarily composed of calcium and phosphate minerals. When the mouth’s environment drops below a critical pH threshold of approximately 5.5, the minerals in the enamel begin to dissolve rapidly into the acidic liquid.
Since most soft drinks measure well below this 5.5 threshold, each sip initiates the demineralization process. The constant bathing of teeth in these low-pH beverages strips away the protective enamel layer. This gradual dissolving leaves the underlying dentin exposed, which can lead to increased sensitivity, discoloration, and a higher risk of developing cavities. The damage is a function of both the drink’s low pH and the frequency and duration of exposure, meaning sipping a soda over a long period is especially damaging.