Citric acid is a weak acid that originates from citrus fruits. It is used as a natural food preservative, and to add flavoring to food. Many sour candies get their mouth-puckering properties from salts that are derived from citric acid. Citric acid also has other applications, and is used for uncommon uses in many products and fields of work.
Tobacco is a green leafy plant with a lot of chlorophyll. Chlorophyll is alkaline, and this alkalinity gives cigarette smoke harsh flavors. Citric acid is added to tobacco during processing, to lower the leaves' alkalinity.
Citric acid is also added to cigarette paper to control the rate at which it burns. This treatment allows the paper and tobacco to burn at the same rate.
Fossil Fuel Power Plants
Citric acid chemically bound to ammonia is used to clean metal oxidation from steam boilers in fossil fuel power plants. The citric acid eats through oxidation deposits. It is safe to dispose of the citric acid slurry by burning or rinsing with lime.
Citric acid is used in many pharmaceutical applications. It is often used to flavor syrups and suspensions. The largest use for citric acid in medicine is for the bubbling effect that it results when combined with carbonates and bicarbonates. This is most commonly seen in antiacids and other tablets that bubble when dropped into water before consumption. Besides making the medication more flavorful, citric acid also enables the body to absorb the medication that it is combined with more effeciently.