Color of Fe2O3

[mongo blongo]

I make my Fe2O3 using Ammonia (9%) added to a solution of Iron II Sulphate. I then filter and cook the ppt which is oxidized by the air.
Each batch of the fully dry Fe2O3 ends up as a slightly different colour. I have had from light brown to dark red to bright orange.
Does anyone know why this is?
I was thinking that maybe a different % of the ppt is oxidized in each batch which could mean different amounts of iron is produced in a thermite reaction?
Any ideas?

[Marvin]

There are quite a few factors that might affects the result. How much water is in the final product, how hot are you cooking it? also how much of the material actually oxidises, FeO is pretty stable and I'm not sure how much roasting, or at what temperature is required to oxidise it. The partical size of ppts has a lot to do with aparent colour and how this is affected by the roasting Ive no idea. Add to that any ammonium sulphate/ferrous sulphate left in after filtering, the ammonia would probably be driven off leaving an acid to attack the oxide, which at a higher temp would itself be driven off. A lot of things could be going on that might affect the product, and without testing you cant be sure if its superficial or not.

[russian_chemist]

Thats the thing with making a compound, there are so many variables the outcome of the elements has to play against it could be anything.

The only thing that is a certain for me in colour is when i deal with one Element. Be it AN or whatever.

with fe203 i always see it come out the same colour as the brine of prilled Ammonium Nitrate after a good crystalisation. That is always the same for me.

Good luck

[mongo blongo]

AN is not an element and it should be white. :)
There is no particle size until it's dried (the ppt is like a slurry). There is little water in the ppt as I squeeze as much water out before cooking. I use a cast iron pot on a camping gas burner.
This still leaves the mistery of what factor changes the color.
Heat is most probably the factor. I say this because bits of the ppt land on the floor (cold) and it always seems to turn out bright orange stain rather than a darker red from the same batch.