woelen

A project is not the same as an experiment. In a project, you work towards a pre-defined goal. Any project in any science is welcome here. If you have built a nice device, have written a nice piece of software, or have achieved a nice result after a thorough investigation, please let us know about it. In this section we do not want oneliners like "I have built a rocket, look how awesome it is". Threads on projects should give detailed descriptions on how you proceeded, such that others can benefit from the info. Discussions on how to achieve a certain goal also are very helpful. Helping each other with projects adds even more fun to working on them. I also want to add that this should not become a place with just a lot of links to other sites. What we want to see here is discussion of YOUR projects and the things which really raise YOUR interest.

In this forum every piece of apparatus, devices, glassware, etc. can be discussed. Properties of the equipment, ways to make special equipment from standard products, creative use of standard products in a special way, all this kind of things can be discussed here. We do not appreciate threads with pointers to manufacturers of certain equipment, this is not meant to be a forum, filled with advertisements. There is no objection of mentioning a certain company, but it must be in the context of useful information about the device or apparatus being discussed. We would really love to see creative ideas of how the functionality of hard to obtain devices can be mimicked with the help of easier and cheaper devices. That would be the true spirit of a thread in the amateur science forum. The only guidelines for the equipment forum is that the equipment must be something, used in (amateur) science. Discussion about equipment, needed for certain sports, outdoor activities, parties, weapons, etc. are not at the right place in this forum. Discussion of illegal devices is not allowed and if dangerous devices are discussed, then explicitly mention the risks of making/using them.

This is the place, where you can write about the experiments YOU have done, or are planning to do. This is not the place to write about something, which others have done, and it also is not the place to talk about some school lab, which you have to do. It should be about your own experiences, you have chosen out of interest. What we want to achieve with this forum is that people actually DO science and not only talk about science. Experiments can be described for all sciences. The most obvious thing may be chemistry, physics, electronics. But also mathematical experiments (e.g. computing and investigating properties of certain mathematical objects, recreational mathematics) and software experiments can be described here. Everything, which is fun, which is your choice to do, and which you want to share with others is welcomed here. The only guideline is that the described experiments must not involve illegal actions and if an experiment imposes a certain risk, then this must be stated explicitly.

Why doesn't it exist? That is an interesting question. There definitely is a pattern among all transition metals. All first row transition metals are most stable in lower oxidation states, while the second and third row transition metals are more stable in their higher oxidation states. E.g. V - Nb - Ta. Vanadium has extensive aqueous chemistry for +2, +3, +4 and +5 oxidation state, +5 is actually a fairly strong oxidizer. Nb only has fleeting existance in the +4 oxidation state in aqueous chemistry, +5 is by far the most stable oxidation state, and Ta is more or less limited to the +5 oxidation state, and only under very specific anhydrous conditions it exists in lower oxidation states. The effect is more marked with Cr - Mo - W. Cr is strongly oxidizing in the +6 oxidation state, while for Mo and W this is the most stable oxidation state. With Mn - Tc - Re this effect is even stronger. Permanganate is one of the strongest common oxidizers, while pertechnate and perrhenate are not oxidizing. I do have some ammonium perrhenate, and that chemical is rather inert. Only strong reductors, like sodium borohydride and metallic zinc in acid (nascent hydrogen) are sufficiently strong reductors to reduce the ReO4(-) ion to a lower oxidation state. The triad Fe - Ru - Os is the turn-over point. Fe(VIII) would be so strongly oxidizing, that it cannot exist anymore in normal environments. Molecules or ions with this would be so unstable that they fall apart through internal oxidation/reduction. Even iron(VI) already is very strongly oxidizing. On the other hand, RuO4 is only a moderately strong oxidizer and the same is true for OsO4. Ru(VI) is quite stable in alkaline environment, Ru(VII) is quite stable in acidic environments. For the further transition metals, a similar thing is true, but less pronounced. Usually the first row allows oxidation states +2 (and sometimes +3) and the higher rows then allow +3 and sometimes +4. Platinum also allows +6, but that is an extremely strong oxidizer, e.g. PtF6 is capable of oxidizing oxygen. I think that really understanding this pattern requires quantum mechanics. What I did is just describing observations, QM computations, however, reveal these properties.

I have the book "Chemistry of the Elements" and this books says that no compounds of iron(VIII) have been isolated and confirmed by independent groups. So, any compounds like FeO4 or K2FeO5 are very doubtful. I think that no iron(VIII) compounds exist, and certainly not at room temperature. ================================================== For layout: Use [ ce]...[ /ce] sections: [ ce]K_{2}FeO_{4}[ /ce] ---> [ce]K_{2}FeO_{4}[/ce] [ ce]CrO_{4}^{2-}[ /ce] ---> [ce]CrO_{4}^{2-}[/ce] You need to skip the spaces after the [ of course. See also here: http://www.scienceforums.net/forum/showthread.php?t=10188

My single favorite. If you want to play around in a practical way with the borders of mathematics (e.g. numerical mathematics, number theory, prime numbers, etc.), using your own software, then have a look at this: http://www.swox.com/gmp It really is great for mathematics hobbyists and researchers, who write their own software. A perfect piece of work.