Acid Blue 9 (CI 42090) is a chemical compound, a dye mainly used in cosmetics and is better known by the name  or Brilliant Blue FCF or FD&C Blue No. 1.

It appears as a powder or blue liquid.

The name defines the structure of the compound:

• CI stands for Colour Index, a reference database maintained by the Society of Dyers and Colourists and the American Association of Textile Chemists and Colourists. The Colour Index assigns unique numbers to each dye or pigment.
• 42090 is the specific Colour Index number assigned to a synthetic blue dye known as FD&C Blue No. 1 or Brilliant Blue FCF.

The synthesis process takes place in different steps:

• Production of basic compounds. The first stage begins with the production of basic compounds such as aniline, a benzene derivative, in reaction with other chemicals to produce a compound called sulphanilic acid.
• Diazotization. Sulphanilic acid is diazotised by converting an amine group of sulphanilic acid into a diazonium compound.
• Coupling. The diazonium compound is coupled with another compound, typically an H acid (8-amino-1-naphthol-3,6-disulphonic acid). This coupling reaction leads to the formation of the bright blue dye FCF.
• Purification. The dye is purified, typically through a washing and filtration process.

Cosmetics

It was admitted to the list of authorised colourants in cosmetic products by Directive 76/768/ECC.

It is used as a direct colouring agent in hair colouring products. Its concentration in the finished cosmetic product must not exceed 0.5%. It is also subject to cosmetic restrictions IV/63 and III/190.

Food

In the food industry, it is included in the list of colouring food additives under the number E133. In 1970 FAO/WHO Expert Committee on Food Additives established an acceptable daily intake (ADI) of 0-12.5 mg/kg body weight. The Scientific Committee on Food of the EEC recommended an ADI of 10 mg/kg body weight in 1983.

CI 42090 Acid Blue 9 studies

• Molecular Formula: C₃₇H₄₂N₄O₉S₃
• Molecular Weight: 782.942 g/mol
• UNII: 86R7G3C26F
• CAS: 2650-18-2  1334-07-2  29519-65-1  37307-55-4  37307-56-5  37307-78-1  51609-24-6  55819-29-9  86924-52-9  99149-43-6  511534-54-6
• EC Number: 220-168-0  223-339-8
• PubChem Substance ID 329769043
• MDL number MFCD00012141
• Colour Index Number 42090

Synonyms:

• FD&C Blue No. 1
• CI 42090
• C.I. Acid Blue 9
• Acid Blue 9
• E133
• Kiton Pure Blue L
• Pro-Jet Blue OAM
• Erioglaucine (VAN)
• Daiwa Blue 109H
• Japan Blue 205
• Eriosky Blue
• Amacid Blue FG Conc
• Duasyn Acid Blue AE
• Orient Water Blue 9
• Schultz No. 770
• Caswell No. 007A
• CI Direct Brown 78
• Edicol Supra Blue E6
• Vitasyn Blue AE 85
• AF Blue No. 1
• Alphazurine (indicator)
• Xylene Blue VSG
• Acid Sky Blue A
• Alphazurine FG
• Erioglaucine E
• Alphazurine FGND
• Neptune Blue WF
• Fenazo Blue XR
• Patent Blue AE
• Calcocid Blue EG
• Kiton Blue AR
• Neptune Blue BRA
• Patent Blue 2Y
• Tortrazine C extra
• Calcocid Blue 2G
• Water Blue 9
• Bucacid Azure Blue
• Hidacid Azure Blue
• Acid Blue AE-SF
• Bleu Brilliant FCF
• Brilliant Blue Lake
• Aizen Brilliant Blue FCF
• Maple Brilliant Blue FCF
• C.I. Direct Brown 78
• Triantine Light Brown 3RN
• Acilan Turquoise Blue AE
• Peacock Blue X-1756
• CI ACID BLUE 9
• CI Acid Blue 9, diammonium salt
• D and C Blue No. 4
• Duasyn Acid Blue AE-SF
• A.F. Blue No. 1
• C.I. Acid Blue 9, diammonium salt
• Dolkwal Brilliant Blue