Carmine Blue V
Patent blue is aniline dye and it is one of the most common dyes used. It is a sodium or calcium salt of diethylammonium hydroxide inner salt. It has the chemical designation of (4-(alpha-(p-(diethylamino)phenyl)-2,4-disulfobenzylidene)-2,5-cyclohexadiene-1-ylidene)diethylammonium hydroxide. Patent blue was developed by Guerbet and approved by Health Canada on December 31, 1979. The isomer isosulphan is used in the United States for the same indications than patent blue.