Iron Oxide Black, known as iron oxide black, is chemically classified as an inorganic colorant. This pigment is composed primarily of ferrous-ferric oxide (Fe3O4) and is widely used in various industrial and cosmetic applications due to its distinctive black color and excellent stability.
Chemical Name
oxoiron;oxo(oxoferriooxy)iron Iron Oxide Black
Chemical Composition and Structure
Iron Oxide Black is an inorganic compound with the chemical formula Fe3O4. It consists chiefly of ferrous-ferric oxide, which includes iron in both the +2 and +3 oxidation states combined with oxygen. This composition gives the pigment its characteristic black color.
Physical Properties
This pigment typically appears as a fine black powder. It has a high density and excellent covering power. Iron Oxide Black is known for its chemical stability, resistance to light and heat, and inert nature, making it suitable for long-lasting applications. Its opacity and strong tinting strength make it a versatile pigment for various uses.
Iron Oxide Black is an insoluble powder but miscible in oils and water. It has high covering power and high tinting strength. It is easily dispersible, shows excellent light fastness and resistance to external weathering. Non-toxic, non-irritating.
Iron oxide and hydroxide are chemicals of various colors used as food additives in the food industry and are labeled with the number E172 as food additives.
The complete table includes:
- E172 (i) black iron oxide, CI 77499
- E172 (ii) red iron oxide, CI 77491
- E172 (iii) yellow iron oxide, CI 77492
Typical characteristics of commercial dyes:
Item | Red | Yellow | Black | Green | Orange | Blue | Brown |
Content % | ≥96 | ≥86 | ≥90 |
| ≥88 |
| ≥88 |
Oil absorption ml/100g | 15-25 | 25-35 | 15-25 | 25-35 | 20-30 | 25-35 | 20-30 |
Res.on 325 mesh % | ≤0.3 | ≤0.3 | ≤0.5 | ≤0.3 | ≤0.3 | ≤0.3 | ≤0.3 |
Water soluble salts % | ≤0.3 | ≤0.3 | ≤0.5 | ≤0.3 | ≤0.3 | ≤2.5 | ≤0.5 |
Moisture % | ≤1.0 | ≤1.0 | ≤1.0 | ≤1.0 | ≤1.0 | ≤1.0 | ≤1.0 |
PH value | 3-7 | 3-7 | 5-8 | 6-9 | 3-7 | ≥6.0 | 4-7 |
Tamped apparent density g/cm3 | 0.7-1.1 | 0.4-0.6 | 0.8-1.2 | 0.4-0.8 | 0.4-0.6 | 0.4-0.8 | 0.8-1.2 |
Particle Shape | Spherical | Acicular | Spherical | Irregular | Irregular | Irregular | Irregular |
Dye Strength % | 95~105 | 95~105 | 95~105 | 95~105 | 95~105 | 95~105 | 95~105 |
Dye Difference △E | ≤1.0 | ≤1.0 | ≤1.0 | ≤1.0 | ≤1.0 | ≤1.0 | ≤1.0 |
Industrial surface treatments:
- With Triethoxycapilisilane, are easily dispersible in oil, has optimal hydrophobicity.
- With Lauroyl Lysine has optimal skin affinity, is hydrophobic and will look smooth and soft.
- With Perfluorooctyl Triethoxysilane is suitable for long lasting makeup products, excellent hydrophobicity and oleophobicity.
- With Titanium dioxide you can create different shades of color, but it is a chemical compound that is harmful to human health.
Chemical Industrial Synthesis Process
- Preparation of reagents. The main raw materials include ferrous sulfate (FeSO₄) and ferric sulfate (Fe₂(SO₄)₃), along with an oxidizing agent such as air or hydrogen peroxide.
- Synthesis of ferrous-ferric oxide. The production of Iron Oxide Black begins with the precipitation of ferrous-ferric oxide. Ferrous sulfate and ferric sulfate are dissolved in water and oxidized by adding an oxidizing agent.
- Formation of the precipitate. The solution is treated to form a precipitate of ferrous-ferric oxide (Fe₃O₄), also known as magnetite.
- Filtration. The resulting suspension is filtered to separate the solid precipitate from the aqueous solution.
- Washing. The ferrous-ferric oxide is washed with deionized water to remove any soluble impurities.
- Drying. The washed ferrous-ferric oxide is dried at controlled temperatures to remove residual moisture and obtain a dry powder.
- Grinding. The dried ferrous-ferric oxide is ground to obtain a fine and uniform powder. This step may involve the use of ball mills or other grinding machinery.
- Classification. The dried powder is classified to ensure a uniform particle size. This step may involve sieving or the use of air classifiers.
- Stabilization. The Iron Oxide Black powder is stabilized to ensure its stability during transportation and storage, preventing oxidation and aggregation.
- Quality control. The Iron Oxide Black undergoes rigorous quality testing to ensure it meets standards for purity, color intensity, and safety. These tests include chemical analysis, spectroscopy, and physical tests to determine particle size and rheological properties.
What it is used for and where
Cosmetics
Restricted cosmetic ingredient as IV/137 a Relevant Item in the Annexes of the European Cosmetics Regulation 1223/2009. Substance or ingredient reported:
- Iron Oxide Black. Wording of conditions of use and warnings: Purity criteria as set out in Commission Directive 95/45/EC (E172)
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.
Iron Oxide Black is used in cosmetic products such as eyeliners, mascaras, eyeshadows, and foundations due to its intense black color and high opacity. It provides long-lasting color.
Applications.
Cosmetics, construction, paints, detergents, waterproof flooring, ceramics, PVC, plastics, glues, pharmaceuticals, medicine.
Paints and Coatings: In the paint industry, iron oxide black is used to achieve deep black shades and enhance UV resistance. Its stability and strong tinting properties make it ideal for both decorative and protective coatings.
Plastics and Polymers: This pigment is employed in the production of plastics and polymers to improve color uniformity and opacity. It is commonly used in products like automotive parts, packaging materials, and consumer goods.
Ceramics and Glass: Iron Oxide Black is used in the production of ceramics and glass to achieve stable black colors. It is particularly valued for its resistance to high-temperature processes.
Inks: The pigment is also used in printing inks to produce intense black colors, ensuring high-quality and durable prints.
Ultraviolet rays from the sun cause skin aging and smartphones emit high-energy visible light from which you should protect yourself. Iron oxides (yellow, red and black) in sunscreens have the property of effectively blocking high-energy visible light especially when combined with zinc oxide (1).
Safety
Iron Oxide Black is generally considered safe for use in consumer products when handled according to proper safety procedures. It is important to avoid inhalation of the powder and minimize direct contact with skin and eyes (1).
Studies
Ultraviolet rays from the sun cause skin aging and smartphones emit high-energy visible light from which you should protect yourself. Iron oxides (yellow, red and black) in sunscreens have the property of effectively blocking high-energy visible light especially when combined with zinc oxide (1).
As regards food safety, being an additive also added in fruits and vegetables, for these foods a maximum permissible level of 6 milligrams per kilo body and the formula "enough" in 48 categories of food (Regulation (EC) No 1333/2008). Within these categories of foods, iron oxides and hydroxides are allowed in liquid food supplements, food supplements in syrup, in solid form, including capsules and tablets and similar forms, excluding chewable. However, EFSA recommends further scientific analysis (3).
Iron oxide CI 77499 studies
- Molecular Formula : Fe2O3 Fe2H6O3
- Molecular Weight : 159,69 g/mol
- CAS : 1309-37-1 1332-37-2
- UNII
- EC Number: 215-168-2
- DSSTox Substance ID:
- MDL number
- MFCD00011008
- PubChem Substance ID 329753614
- InChI=1S/2Fe.3H2O/h;;3*1H2
- InChl Key YOBAEOGBNPPUQV-UHFFFAOYSA-N
- SMILES O.O.O.[Fe].[Fe]
- IUPAC iron;trihydrate
- ChEBI
Synonyms:
Iron Oxide Black
Pigment Black 11
Black Iron Oxide
CI77499
E172 (i)
Ferric oxide
References____________________________________________________________________
(1) Aquilina, G., Azimonti, G., Bampidis, V., de Lourdes Bastos, M., Bories, G., Chesson, A., ... & Wester, P. (2016). Safety and efficacy of iron compounds (E1) as feed additives for all species: ferric oxide based on a dossier submitted by Poortershaven Industriële Mineralen BV. EFSA JOURNAL, 14(6), 1-26.
Abstract. The additive under assessment, ferric oxide, contains between 57% and 69% iron (Fe). The EFSA FEEDAP Panel could not conclude on the safety of ferric oxide for the target animals owing to that (i) the application of ferric oxide red is for all animal species, (ii) lifetime administration to animals is not excluded and (iii) a sufficient biological and toxicological database was not available. Regarding (i) the very low absorption of iron from the ferric oxide by target animals and (ii) the homoeostatic regulation of iron metabolism in animals, any influence of feeding the ferric oxide on the iron content of edible tissues and products is not expected. The use of ferric oxide in animal nutrition is unlikely to result in a direct exposure of the consumer to this oxide. Consequently, the supplementation of feed for food-producing animals with ferric oxide would likely not constitute a risk to consumers. Ferric oxide is an irritant to skin and eyes by mechanical action. Owing to the nickel content in the additive, the ferric oxide
(2) Bernstein EF, Sarkas HW, Boland P. Iron oxides in novel skin care formulations attenuate blue light for enhanced protection against skin damage. J Cosmet Dermatol. 2021 Feb;20(2):532-537. doi: 10.1111/jocd.13803.
(3) EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS)
First published: 08 December 2015 https://doi.org/10.2903/j.efsa.2015.4317
Iron Oxide Black 
Hydrogen peroxide as oxidizing agent
