ferrocene

Thanks for this, Woelen - interesting points you raise, quite a few of them new to me. The evidence certainly suggests that Fe (VIII) does not exist. However, I remember reading (quite some time ago) why KBrO4 and the perbromates could not possibly exist - but that didn't stop them from existing. I also noted a detailed description of OsF8 - and subsequently a report saying it definitely does not exist. I am curious then as to what might be happening when Fe2O3, KOH and a large excess of KNO3 are heated. (Unfortunately, I didn't copy the equation that Mellor gave - but this was many years ago) I remember clearly that a dark green melt was produced, that it turned white when it cooled and solidified (contrary to what Mellor said). I cannot think of any iron compound which would behave in such a way under those conditions. There are a number of iron compounds which are white, but I can't think of any which would fit this particular bill. Unfortunately, I'm not in a position to try this experiment again.

Thanks for this. Who is the book's author and when was it written? If my memory serves me correctly, Mellor stated that K2FeO5 was obtained by heating Fe2O3, KOH and a large excess of KNO3. A green melt is obtained, which becomes a green solid on cooling. When I tried it, I certainly obtained a green melt, but it became white when cooled. Sadly, I can't remember anything else. I had doubts then about the existence of iron (VIII). If it doesn't exist, then I wonder why not?

Does anyone have information about the chemistry of iron in oxidation state VIII ? (The chemistry of iron (VI) is well documented) Mellor’s Treatise on Inorganic Chemistry devotes only a couple of paragraphs to the preparation of potassium perferrate K2FeO5 and iron tetraoxide FeO4. I remember as a teenager trying out the experiments described, but didn’t obtain the same results. I have googled extensively but found nothing of help. (How do I convert a number to sub-script?)