Acid Black 2 is a chemical compound, a synthetic azine dye known as CI 50420.

Azine is a compound resulting from the reaction of two different carbonyl compounds with hydrazine.

Chemical Name: 

disodium;4-amino-5-hydroxy-3-[(4-nitrophenyl)diazenyl]-6-phenyldiazenylnaphthalene-2,7-disulfonate

Processo industriale di sintesi chimica

• Preparation of reagents. The main raw materials include aniline, nitrobenzene, and concentrated sulfuric acid.
• Synthesis of intermediates. The production of CI 50420 begins with the nitration of aniline to form nitroaniline derivatives. These intermediates are crucial for subsequent synthesis steps.
• Reduction. The nitroaniline derivatives are reduced in the presence of a reducing agent, such as sodium sulfide, to obtain the corresponding amine compounds.
• Polymerization. The amine intermediates undergo a controlled polymerization reaction in the presence of an oxidizing agent, such as hydrogen peroxide, to form the nigrosine pigment.
• Sulfonation. The crude nigrosine is treated with concentrated sulfuric acid to introduce sulfonic groups into the molecule, making the pigment water-soluble and enhancing its coloring properties.
• Neutralization. The sulfonated mixture is neutralized with a base, such as sodium hydroxide, to obtain the sulfonated nigrosine salt.
• Purification. The crude CI 50420 product is purified using techniques such as filtration and crystallization to remove impurities and achieve a high-purity colorant.
• Stabilization. The purified CI 50420 is stabilized to ensure its stability during transportation and storage, preventing degradation and oxidation.
• Quality control. The CI 50420 undergoes rigorous quality testing to ensure it meets standards for purity, color intensity, and safety. These tests include chemical analysis, spectroscopy, and microbiological testing.

What it is used for and where

Cosmetics

Restricted cosmetic ingredient as IV/84 (CI 50420) II/1359 (CI 50420: when used as a substance in hair dye products) a Relevant Item in the Annexes of the European Cosmetics Regulation 1223/2009. Substance or ingredient reported:

• Sulfonated nigrosine color

Cosmetics - INCI Functions

• Colorant. This ingredient has the function of colouring the solution in which it is inserted in a temporary, semi-permanent or permanent manner, either alone or in the presence of the complementary components added for colouring.

Safety

It is an ingredient that has some important health-related contraindications: it should not come into contact with mucous membranes.

 It is an ingredient that makes the final product more attractive from an aesthetic point of view, but can pose a potential health risk with undesirable side effects especially when used continuously as it can be absorbed through the skin or mucous membranes.

Molecular Formula  C₂₂H₁₄N₆Na₂O₉S₂

Molecular Weight    616.5 g/mol

CAS    8005-03-6

UNII    SZT789770M

EC Number  213-903-1

DTXSID1020934

Synonyms:

CI 50420

Naphthol Blue Black