[treelove]

Any titration or anything like that I could do?

[Arkcon]

That's a tough one, as asked, there are too many possibilities.  Can you burn it?  Then you can measure oxygen compounds afterward.  Is all th eoxygen reduced, or oxidized?  Then you can do a redox titration.  But that question of mine, itself, isn't specific enough -- how reduded or oxidized, it may no be possible to find a reaction.  You might want to consider ICP.  http://en.wikipedia.org/wiki/ICP-AES

[treelove]

Yeah I did burn it. I threw it in a flame but it didn't really change colors. My sample looks like a light green or bluish crystal. When I took it out of the flame it had melted together into a rock type thing. I broke it apart and I saw white, reddish and brown powder. I know it contains iron and I'm guessing oxygen. I found it had about 14-15% Fe, now I need to see how much oxygen is in it.

[Arkcon]

When I said burn, I meant that you wanted to know the oxygen content of a carbohydrate, for example, and could measure oxygen consumed, vs water and carbon dioxide produced.

[Borek]

Please give us a context for this question - what kind of a lab it is, and what are you asked to do.

[treelove]

find the molecular formula of an unknown compound... looking to find if there's oxygen in it and how much. it's not organic.

[Borek]

Is your sample soluble in water? Acid? Base?

[treelove]

yes it's soluble in water and i'm pretty sure it's an acid. my best guess is ferrous ammonium sulphate but i need to prove it.

[Borek]

Google qualitative inorganic analysis.