Citric acid is soluble in water to a great degree. In water of a temperature of 212 degrees Fahrenheit, 84 percent of the citric acid added to the solution is dissolved.
At lower temperatures, citric acid retains its high solubility. For example, at 68 degrees Fahrenheit, close to normal room temperature, citric acid has a solubility in water of 59 percent. Because of its high solubility, citric acid is preferred in its anhydrous crystal form by the food industry, where it is widely used to add acidity to products. The anhydrous crystals are much more stable and can be stored for long-term, industrial use without fear of the acid melting away due to contact with moisture in the air.