FD & C Red 40 Lake

Allura Red AC is a red azo dye that goes by several names, including FD&C Red 40.[1] It is used as a food dye and has the E number E129.

It is usually supplied as its red sodium salt, but can also be used as the calcium and potassium salts. These salts are soluble in water. In solution, its maximum absorbance lies at about 504 nm.[2]: 921 

Allura Red, FD&C Red No. 40 is manufactured by coupling diazotized 5-amino-4-methoxy-2-toluenesulfonic acid with 6-hydroxy-2-naphthalene sulfonic acid in an azo coupling reaction