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Metallic osmium in solid form is nontoxic. But as the compound osmium tetroxide, OsO4, it is extremely toxic, highly corrosive, extremely irritant to mucous membranes. Often considered as one of the most toxic compounds of inorganic chemistry. But then nickel, as tetracarbonyl nickel ( Ni(CO)4 ) could be considered even worse.

No. That "extremely tiny amount of cyanide gas can kill a person" is definitely a myth. Hydrogen cyanide is not extremely toxic. However, under some unfortunate circumstances, the death can be rapid, within minutes.

Highly improbable, although not impossible. Add excess ferrous sulfate, + eventually some ferric nitrate, dilute with plenty of water. Then it will be highly improbable that it will present a hazard of any kind. Of course, reasonable quantities are assuemd, some hundreds of grams at most. It is unlikely to present some hazard, unless the quantity is in orders of tens or hundreds of kilograms.

Nope! The hexacyanoferrate(II)ion is a very stable komplex, which is the reason that it is almost nontoxic (or at least has very low toxicity). On the contrary, one classic way of destructing dangerous alkali cyanide spills is by adding Fe2+ (as solid FeSO4.7H2O). The ferrous ion reacts with the free cyanide ions, giving the very stable complex hexacyanoferrate(II)ion. And this has a very low level of toxicity. Even better; adding some Fe3+ and you get a precipitate of Turnbull blue (=Prussian blue), a complicated phase often described as ~KFeFe(CN)6 (s). But it is possible to convert solid potassium hexacyanoferrate(II) (or hexacyanoferrate(III) ) to KCN by melting it. The potassium hexacyanoferrate is decomposed to nitrogen, ferric carbide, and potassium cyanide. And, boiling a water solution of hexacyanoferrate(II) or hexacyanoferrate(III) with acid gives gaseous hydrogen cyanide. Then you are in a lot of troble!

In what respectis is it "most noble"? Relative what? Sodium is more noble (i.e. less reactive) than lithium with respect to hydrogen, nitrogen, carbon. But sodium is less noble (i.e. more reactive) than lithium with respect to halogens, chalcogens, acids. We see that when reacting sodium and lithium respectively with water. Sodium reacts much more violently, even with ignition, if finely divided or larger chunks. Lithium does not ignite, although the reaction is vigorous.

The term nobility is not uniqely defined from a chemical point of view. Ir is not attacked by aqua regia in any concentration, not even finely divided metal. Au is readily attacked by and dissolved in aqua regia (fast), Pt is dissolved but much slower. But, Au is not oxidized in air at any temp, Ir is attacked even below 1000 deg C, IrO2 is formed. So, which one of these 2 metal is "the most noble"? It is a question of reactivity, and then the reactivity must be specified/defined towards/relative some other species. The electrochemical series is for species (not only metal ions) in water solution. The reason that the redox couple Li+/Li has a lower voltage than Na+/Na, which in turn is lower than K+/K, is solvatization. In water solution that will be hydratization. The result is that by the relative voltages of alkali metal ions i water solution, it looks like Li is the least noble alkali metal, and Cs is the most noble of them. We know from the reactivity of alkali metals towards oxygen and water that it is the opposite situation, at least for the metals exposed to air or moisture. And, the reactivity of alkali metals is not uniqely defined. The reactivity of alkali metals towards halogens, chacogens, acids (and water) increases with increasing atomic number. But, the reactivity of alkali metals towards hydrogen, nitrogen, carbon decreases with increasing atomic number. So Li is the most reactive alkali metal toward nitrogen, not Cs. Li reacts with atmospheric nitrogen at roome temperature and a atmospheric pressure.

Dont even think about it. The melting point for Li is 180,5 deg C, with a serious risk for ignition if the metal is exposed to air. I have once melted Li under (or rather over!) paraffinum oil, and it was just terrible: the oil was very hot, some nasty smoke emanating from the oil, turning somewhat brown-yellow (decomposiing) and the molten metal floating on top of it, totally impossible to get some control over. And with a severe risk of ignition all the time. I guess I was lucky that the bloody metal didn´t ignite right in my face. Don´t handle molten Li, it may ignite right up in your face!

The worst thing I have smelled is POCl3. There was no smell, just an intense burning pain up my nose, my face became violet, black and red. A friend thought I was going to faint. I never did, but the pain was tremendous. The smell was distorted in a strange way, everything smelled like dirty soil. Totally awful. it took about 4 hour before the pain had gone, and the smell was totally recovered.

"Ferrofluid Neodymium Rare Earth Magnetic Liquid - 8 ounces What is Ferrofluid? In short, it is a liquid that responds to magnets and magnetic fields. The longer answer is ferrofluid is an extremely fine powder, coated with a soap-like material called a surfactant, suspended in a mineral oil liquid base. The resulting magnetic suspension is called a ferrofluid. When no magnetic field is present, ferrofluid behaves and flows like a normal liquid. However, when a magnet or magnetic field is introduced, the ferrofluid is attracted to the field. Spikes then form along the magnetic field lines when the magnetic surface force exceeds the stabilizing effects of fluid weight and surface tension. " http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=6193681124&category=413&tc=photo

I am using pure paraffinum oil (thick viscous oil) for alkali metals. This oil is the purest, and with much better preserving properties than ligroin, kerosene etc. For lithium a small polyethylene mesh just above the metal pieces is added. This is to submerge the metal pieces in the oil, well below the surface. Stored in a small thickwalled glas bottle. And this bottle in a metal can, filled with vermiculite. Finally, all alkali metal storage bottles locked in a fire proof safe. By experience I have found that even sodium is preserved unattacked by moisture and oxygen for years under this oil. Potassium is more sensitive, will slowly corrode surfacially. But the real problems are with the 5 reactive lanthanides (La,Ce,Pr,Nd,Eu)! I have found that neodymium is just totally hopeless under paraffinum oil, corrodes heavily. The only method for these metals in the long run is packing under dry argon in sealed glass ampoules.

This one was fun! eating gallium! I haven´t tried that (although I once tasted 1M KCN-solution,; totally awful taste!) It´s correct, Ga is non-toxic by any administration route. Gallium has a very low vapour pressure, and this is in fact used for purifying Ga from more volatile metals like Zn. Zn has a much higher melting point than Ga, but a much lower boiling point. So, by heating Ga (suspended in a radio frequency coil) the Zn gasses of from the melt, but Ga does not. I once saw a listing of vapour pressures for different metals at room temp, and for molten Ga it was something like p(Ga) = 10^-36 atm. That is, no vapour pressure at all at room temp.

By destilling HClO4 you end up with an azeotrope containing ~70% HClO4. Removing water from this is not easy. And highly dangerous. One way of producing water free HClO4 is by treating solid KClO4 with conc H2SO4. Then you get HClO4, no water content. This is not the same as the azeotrope ~70% HClO4. And certainly not the same as chlorine (VII) oxide Cl2O7. It is a completely different fact that Cl2O7 react with water, producing HClO4. "Cl2O7+H2O-->2HClO4. Cl2O7 is perchloric anhydride" Yes, but this does not mean that HClO4 and Cl2O7 is the same thing. SO3 reacts with water, producing H2SO4. But no one would say that sulfur trioxide (sulfuric acid anhydride) is the same thing as sulfuric acid. Or that phosphorus pentoxide is the same thing as phosphoric acid. Etc.