Brilliant blue FCF (Blue 1) is a synthetic organic compound used primarily as a blue colorant for processed foods, medications, dietary supplements, and cosmetics. It is classified as a triarylmethane dye and is known under various names, such as FD&C Blue No. 1 or acid blue 9. It is denoted by E number E133 and has a color index of 42090. It has the appearance of a blue powder and is soluble in water and glycerol, with a maximum absorption at about 628 nanometers. It is one of the oldest FDA-approved color additives and is generally considered nontoxic and safe. Production Brilliant blue FCF is synthetic dye produced by the condensation of 2-formylbenzenesulfonic acid and the appropriate aniline followed by oxidation. It can be combined with tartrazine (E102) to produce various shades of green. It is usually a disodium salt. The diammonium salt has CAS number . Calcium and potassium salts are also permitted. It can also appear as an aluminum lake. The chemical formation is C37H34N2Na2O9S3. Related dyes are C.I. acid green 3 (CAS#4680-78-8) and acid green 9 (CAS#4857-81-2). In these dyes, the 2-sulfonic acid group is replaced by H and Cl, respectively. Many attempts have been made to find similarly colored natural dyes that are as stable as brilliant blue FCF. Blue pigments must possess many chemical traits, including pi-bond conjugation, aromatic rings, heteroatoms and heteroatom groups, and ionic charges in order to absorb low energy red light. Most natural blue dyes are either unstable, blue only in alkaline conditions, or toxic; good candidates for further research into use as natural dyes include anthocyanin and trichotomine derivatives. No replacement for brilliant blue FCF has been found for use in beverages. Applications Like many other color additives, the primary use of Blue No. 1 is to correct or enhance natural coloring or to give colorless compounds a vivid hue. In the United States, of the two approved blue dyes (the other being Indigo carmine, or FD&C Blue #2), brilliant blue FCF is the more common of the two. As a blue color, brilliant blue FCF is often found in cotton candy, ice cream, canned processed peas, packet soups, bottled food colorings, icings, ice pops, blueberry flavored products, children's medications, dairy products, sweets soft drinks, and drinks, especially the liqueur Blue Curaçao. It is also used in soaps, shampoos, mouthwash and other hygiene and cosmetics applications. Brilliant blue FCF is