专利蓝V CAS号：3536-49-0

Patent Blue V, also called Food Blue 5, Sulphan Blue, Acid Blue 3, L-Blau 3, C-Blau 20, Patentblau V, Sky Blue, or C.I. 42051 and is a dark bluish synthetic triphenylmethane dye used as a food coloring. As a food additive, it has E number E131. It is a sodium or calcium salt of [4-(α-(4-diethylaminophenyl)-5-hydroxy- 2,4-disulfophenylmethylidene)-2,5-cyclohexadien-1-ylidene] diethylammonium hydroxide inner salt.[clarification needed]; It is not widely used, but in Europe it can be found in Scotch eggs, certain jelly sweets, blue Curaçao, certain jello varieties (though not in actual Jell-O brand products), among others. An important advantage is the very deep color it produces even at low concentration, a disadvantage is that it fades fairly when exposed to light.