Different coloured iron oxide?

[Sonny Jim]

I've recently preapred a batch of Iron Oxide via the elextrolysis of iron, and I'm confused. After emptying the cell, I blowtorched the dried gunk in order to convert it into Fe2O3, but in two different sessions. The thing is, the final product from each heating session has ended up a slightly different colour. One is slightly darker than the other, but lighter than it was before heating. Each batch was heated until it gave off no more gas.

Is this the same chemical? And if so, how come the colour is different?

[mongo blongo]

I did make a thread asking the very same question some time ago because it confused the shit out of me too :).
I have since found out that it is the crystal size that changes the color. It's because on one of your batches you gave it more heat or it took longer to dry than the other.
They make use of this in the pigment industry. They can produce all kinds of color like yellow,red,orange,etc by changing the size of the crystal. They do this by bubbling air through Iron II sulphate solution which will precipitate out iron oxide. They use what are known as seed crystals for the newly forming crystals to latch onto and they mimic the shape and size of the seed crystals. So if they wanted a yellow pigment they throw in some yellow iron oxide crystals to start it off.
The crystals are extremely small so you could not change the color by grinding the crystals.

Seriously dude you should try another way of making Fe2O3! :)
You live in the UK so you could easily find some sulphate of Iron from a garden center or B&Q and some ammonia from hyper-value.
Dissolve as much iron sulphate as you can in some hot water and add some ammonia and filter the green\blue precipitate and dry it (it's Iron hydroxide which will get oxidized by the air into Fe2O3). Much cheaper and less time consuming and you can make like 700g a time.
I hope this helps :)

[Sonny Jim]

Thanks very much. That's cleared a great deal up, and I'll be sure to try that method you mentioned. I was using the electrolysis method because I have aquired a DC converter that has quite a weak power output, but can run for as long as you leave it switched on. Then throw in the multitude of iron junk I have 'borrowed' from the college tech block and it seemed the most convenient way.

Admittadely though, I did not know about the method you suggested, and it sounds a much better idea to me. Thanks again. :D