Anhydrous Citric Acid refers to a tricarboxylic acid that is found in citrus fruits. These are used as an excipient in pharmaceutical preparations due to their antioxidant properties. It maintains the stability of active ingredients that are used as preservatives. Anhydrous Citric Acid is found naturally in citrus fruit such as lemons and limes that are used as a natural preservative that has the water molecules removed and is usually in a dry and powdered formulation.