CHENGYU are exported all over the world and different industries with quality first. Our belief is to provide our customers with more and better high value-added products. Let's create a better future together.
Iron oxide is just rust to you and me, but ferric oxide to chemists. Although it exists in abundance in nature, it is impossible to purify to acceptable safety standards. As a result, all iron oxide today is synthetically prepared. Depending on how iron oxide is prepared, it can develop different colors: yellow, red, brown and black. Different colors of iron oxide depend upon the oxidative state of the iron atom, with Fe+3 appearing brown and Fe+2 appearing red. Different colors of iron oxide also depend upon the amount of water added to the iron atom (iron hydroxides). This variation gives rise to the yellow, red, brown, and black colors.
Iron oxide is an insoluble mineral pigment. Consequently, its use in foods is limited. In comparison, iron oxide is used extensively in the cosmetic industry where it is combined with titanium dioxide to make a host of red, pink, beige, tan, and black colors. It is also combined with mica, making a wide variety of “pearlescent” colors used extensively in the cosmetic industry.
$\begingroup$
How does the color of rust change depending on its makeup and state, or more to the point, how would one put the rust into that state?
If you are looking for more details, kindly visit Iron Oxide Colors for Roofing.
For example, Wikipedia shows Iron(III) Oxide as being red in the α hydrate state and yellow in the β hydrate state, while a brown pigment is shown here as being iron oxide with a +3 oxidation state (which I understand to be Iron(III) Oxide, whose color above depends on its hydration state). Finally, a black pigment can be made using Iron(II,III) Oxide.
So my question is: I have crude brown Fe2O3(aq) (which I made from simple NaCl hydrolysis of iron); If I let it dry I presume I will get brown pigment. What do I have to do to it in order to make it enter the α or β hydration states? Finally, how would one convert Iron(III) Oxide into Iron(II,III) Oxide?
I understand most of this information is explained on the wiki pages that I linked, but I'm having a hard time sorting through it and would love if someone could help me cut through it and let me know what's more or less possible in a very small home lab, as opposed to some sort of industrial process that I likely don't have access to. Thank you for your patience as I begin what I hope to be a wonderful new hobby.
For more information, please visit oxide pigments.