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 and as CI 77492 as colorants.
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.
Applications:
Cosmetics, construction, paints, detergents, waterproof flooring, ceramics, PVC, plastics, glues, pharmaceuticals, medicine.
Yellow Iron Oxide 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.
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
The Panel on Food Additives and Nutrient Sources added to Food provides a scientific opinion re‐evaluating the safety of iron oxides and hydroxides used as food additives (E 172): yellow iron oxide (FeO(OH)·H2O), red iron oxide (Fe2O3) and black iron oxide (FeO·Fe2O3). Brown Iron Oxide has been included in this assessment for completeness, due to its importance as a commercial blend. The Panel considered that the particle size and particle size distribution should be included in the specifications. In 1980, an ADI of 0‐0.5 mg/kg bw/day was established by JECFA. Absorption of iron from iron oxides is low. The acute oral toxicity of iron oxides is greater than 10 g iron oxide/kg bw. From a subacute and a subchronic toxicity study, the Panel identified a NOAEL for red iron oxide of 1 000 mg/kg bw/day, the highest dose tested. Red (Fe2O3) and black (FeO·Fe2O3) iron oxide, both in nano‐ and micro‐form, were positive in in vitro genotoxicity assays in mammalian cells. Due to the limitations of the database, and considering the impossibility to read‐across between iron oxides with different redox state, the Panel considered that the genotoxicity of iron oxides cannot be evaluated based on the available data. Concerning carcinogenicity and reproductive and developmental toxicity, no signs of toxicity were observed in unpublished studies which were not available and could not be evaluated by the Panel. The Panel concluded that an adequate assessment of the safety of E 172 could not be carried out because a sufficient biological and toxicological database was not available. Refined exposure estimates show that exposure to E 172 ranged from 0.03 mg/kg bw/day for infants to 3.7 mg/kg bw/day for toddlers at the mean and from 0.1 mg/kg bw/day for infants to 9.5 mg/kg bw/day for toddlers at the 95th percentile for the non‐brand‐loyal scenario (2).
Iron oxide CI 77492 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:
- CI77492
- E172 (iii)
- Ferric oxide
References_________________________________________________________________
(1) 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.
(2) 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 CI 77492 E172 (iii) 
Hydrogen peroxide as oxidizing agent
