woelen

Which metal ions? Only K(+) is present. That does not catalyze decomposition of H2O2. I2 also does not have any effect, at least not at the low pH involved. I have done this reaction many times and it works like a charm. No evolution of oxygen, 100% oxidation of I(-) and 99+% of all I2 precipitates as a dense and easy to separate solid mass. Really neat and easy. This is one of the best preps I know of I2 from KI or NaI, using only simple OTC chemicals, like 3% H2O2 and 10% HCl. As I stated before, you should not use concentrated acid and H2O2, using that will result in a lot of side reactions.

Well, in fact, the nitrate ion is not needed at all to make your fingers black. Any silver salt will do. I have some silver sulphamate and this equally makes your fingers black, while the sulphamate ion is quite unreactive (inert). What happens is that silver ions are quite strong oxidizers, the silver itself being reduced to metallic silver (causing grey/black stains on the skin) and destroying the skin, which is being oxidized. The nitrate ion hardly has any effect. I know the same effect from any soluble silver salt. Chemically speaking, silver ions and nitrate ions do not react at all. Nitrate in fact is quite stable in aqueous solutions, unless the pH is very low and concentration is high, as in nitric acid. For photographic purposes, silver chloride and bromide are used. The silver then is reduced by the developer and the bromide or chloride remains behind in solution. Black stains also are obtained, when silver chloride is on the skin for a longer time.

Reactivity usually is defined towards another compound. When one says that a certain compound is ver y reactive, then it means that there are many other compounds, which react with it. More precisely, however, one has to state reactivity towards other compounds or classes of compounds. In general, both HF and F2 are very reactive, but F2 can be regarded the more reactive. But there are compounds, for which HF is more reactive. It might be that indeed certain oxides and certain forms of glass or SiO2 are attacked more strongly by HF than by F2.

H2O2 + HCl does not give Cl2 when diluted. Mixing 30% H2O2 with 30% HCl indeed does give Cl2, but mixing 3% H2O2 with 10% HCl does not give Cl2. The H2O2 directly oxidizes the I(-) in that case and when there is excess H2O2, it remains in solution unchanged and it does not oxidize any I2 further. Working with Cl2 is more difficult, because that DOES oxidize I2 further. In dilute aqueous solution, this will lead to formation of iodate and chloride. At high concentration this will lead to formation of ICl4(-) and chloride. I have quite some experience with oxidizing I(-) to I2 and to my experience the dilute H2O2/HCl is a very sure method, with hardly any loss of I2. Because of the low solubility of I2 in water, virtually all of it precipitates from solution (because no I(-) is left for forming I3(-)) and that makes isolation easy. The precipitated slurry then can be heated and the crystals of iodine can be collected on a cold piece of glass. A second heat/collect glass may be needed if you want it really dry. ----------------------------------------------------------------------------------- If you want to play around with ICl2(-) and ICl4(-), then you need to do one of the following: - add potassium iodate to conc. HCl - or add potassium periodate to conc. HCl - or bubble a large excess of Cl2 through a concentrated solution of KI. On my website, I describe the first experiment. The compound KICl2 hardly can be formed, it is too unstable. KICl4 can be made fairly easily, it nicely crystallizes from aqueous solution and is not hygroscopic. It has interesting properties: http://woelen.scheikunde.net/science/chem/exps/exppatt.cgi?compound=potassium%20tetrachloro%20iodate%20(III)

I think this is a very strong point. The average k3wl does not do this kind of experiments, such a person prefers playing around with KNO3 or KClO3 and the common set of reductors like S, sugar and C. There is no fire and smoke at all, only some dark green color. Very dull . For this reason I have no objection against placing a description about this (yes, dangerous) experiment on this forum, while I would never place a description of an experiment with KClO3 and the like on this forum. That kind of experiment would attract kewls and could cause much more harm. People, who do this kind of experiments, tend to be more scientificly interested and have an understanding of the risks. For each experiment I perform, I first think about what could go wrong and what could happen afterwards. If you want much more of this kind of experiments, then have a look at http://www.sciencemadness.org. This experiment is one of the easier and safer ones if you look around over there. But still, there is no problem with all those dangerous experiments, because the people who do so, are very knowledgeable people, who are willing to invest hundreds or even thousands of dollars in equipment and chemicals and who are of a totally different kind than the first k3wl you can meet in the streets. I also learn a lot of them. Why would a k3wl buy selenium (a meagre 30 grams for $9, no fun at all!! he can buy a kilo of KNO3 or S for that and have much more smoke and fire !!), the average k3wl probably never heard of selenium (is that a planet ??).

If you really want to understand the differences between atoms in their formation of compounds, then you have to delve into quantum mechanics. Properties of atoms, most important for their chemistry, are the orbitals, available for bonding and how these orbitals overlap (hybridize) with other orbitals. All 'rules', we learn about the chemical properties, are based on centuries of observations of all kinds of chemical compounds. Only the last 80 years or so, people are understanding the underlying physical principles to a reasonable extent and only the last few decades we have the computational power to explain all macroscopic observations on the basis of quantum mechanical models of atoms and (simple) molecules.

I agree with you, Jdurg. Of course, I'm very careful with selenium and on my website I warn for Se-compounds, but we should not exaggerate on things. Just for fun : This is a very funny definition of toxicity. According to this definition, I think water is the most toxic compound. Suggested daily intake is around 1.5 liters for a grown up healthy person. A dangerous dose, however is 10 liters per day (for many people even much less). That's a ratio of at most 7 : 1, probably even lower .

Jdurg, you're right . Althoug KrF2 is not the most stable compound, it definitely exists and can be stored as a chemical. I must have been confused with argon.

If you want to make free iodine, I would go for adding a dilute solution of HCl+H2O2. This oxidizes all still existing I(-) to I2 and I3(-) also is fully converted to I2. If you use excess H2O2+HCl then all iodine will precipitate out of solution. By filtering you can isolate the I2. Don't mess around with hypochlorite/bleach solutions. This will destroy all your iodide/iodine. Because of its alkalinity, the iodine will be converted to iodate and you'll have even a harder time to isolate the material.

Of course price is not correlated with toxicity, but my point is that the selenium is shipped in an ordinary envelope at very low cost, while for instance I2, but also Ag2O, K2Cr2O7 and many other chems require outrageous hazmat fees, when they have to be shipped overseas. If you can give an explanation for this, then you're welcome. I also found another supplier for selenium (JD Photochem) and this one also sends the material to me without any hazmat hassle. Apparently it is not THAT toxic. But of course, I agree with you that it is toxic and one should not play with it without knowing its risks. But this is true for most chemicals.

If selenium is so horrendously toxic, then why are there still selenium toners in photography, used by many photographers? These are not old-fashioned, removed-from-market curiousities, but you can still purchase them at many ordinary photography shops. Another thing, why can I buy pure elemental selenium for just $9 per 30 grams without any question asked? The stuff even is shipped without any restriction overseas, in just a normal letter envelope for $1.60 US to Europe postage. See http://www.emovendo.net/store/customer/home.php?cat=256 for more info. At this place I purchased a few of these 30 gram packages. On the other hand, if I want to buy 30 grams of I2 from the same seller from the USA (shipping to Europe), then I have to pay hazmat fees like crazy (starting at $20, going up to $150 if quantities are raised somewhat). In practice this seller does not ship I2 at all internationally, because it is not worth the cost and the hassle.

Cu(OH)2 is bright blue. If you use an excess amount of CuSO4, then you'll get pale blue basic copper sulfate, Cu(OH)x(SO4)y, with 0.5x+y=1. On my website I have pictures of the precipitate: http://woelen.scheikunde.net/science/chem/solutions/cu.html Look at the section for oxidation state +2. The bright fairly dark material is Cu(OH)2, the lighter material is basic copper sulfate.

No, you do not need to worry about any selenium escaping from this hot liquid. According to my book (Chemistry of the Elements, from Greenwood and Earnshaw), a cationic species is formed, which dissolves in the sulphuric acid. Because an ionic species is formed, it cannot escape (just like that a solution of NaCl on heating never will give off any NaCl). The exceedingly corrosive ultrahot sulphuric acid is more scary to me. But I agree with you, selenium compounds are quite toxic at higher doses (although you need small doses). Remarkably, the pure element hardly is toxic, it leaves your body unchanged. Compounds like H2Se and SeO2, however, are VERY toxic, much much more than the related compounds H2S and SO2.

Indeed, but did you also read the conditions, under which this is formed and what is needed to keep this stable? For any practical purpose, krypton does not form any compound, the lighter noble gases definitely are even less reactive. Using special techniques, of course, one can make any compound, by placing atoms in an ultracold frozen argon matrix (T < 20K) and keeping them fixed in that matrix. But to my opinion this is cheating. Real chemical reactions at somewhat more common temperatures and normal storage conditions are not known for He, Ne, Ar and Kr. You're right with this, but indeed, the fluorine and the quartz must be perfectly dry. Even trace amounts of water cause it to react. Also, there might be some refractory oxides, which are inert, even to fluorine, but these I place under the rare exeptions I mentioned.

Time to bump this old thread again. I found another way to make red selenium from black selenium. Not for my element collection anymore, but I found it by coincidence. Take some concentrated H2SO4 (96+ %) Add some black selenium. If it is in the form of small corpuscles, then crush it to a powder before adding to the acid. Heat the acid, until it is a mobile liquid like water and faint white fumes are formed. The liquid becomes dark green, due to formation of cationic species of selenium, which are dissolved in the acid. Let acid cool down. It remains dark green and clear. It becomes viscous again, like H2SO4 always is. Pour the acid in a large amount of water. The red allotrope of selenium is separated as a fine brick-red powder. A word of warning to anyone wanting to repeat this experiment: Be VERY careful with heating concentrated sulphuric acid to the temperatures involved in this experiment. Temperatures are well over 200 C. You absolutely must trust your glasswork. Cracking glasswork can be really destructive with this hot concentrated sulphuric acid.

Yes, fluorine reacts with all elements, except helium, neon, argon and krypton. It also reacts with virtually every compound, which is not yet fully fluorinated. There are a few exceptions, but these are rare. With some elements (e.g. the platinum metals) it only reacts very slowly, but even with these it reacts. When fluorine was made first at the end of the 19th century, a platinum anode was used. For each gram of fluorine produced, 6 grams of platinum were corroded away. You can imagine that the person who first made elemental fluorine must have been a wealthy person.

An example of such a peroxo acid is Caro's acid and peroxodisulfuruc acid: Caro's acid: O2S(OH)(OOH), H2SO5 Peroxosulfuric acid: O2(OH)SOOSO2(OH), H2S2O8

Oh no, most hydrocarbons react explosively with F2 and they are broken down completely, forming CF4 and HF. If oxygen is present in them, that will form H2O. The substances, with which fluorine does not react are fluorides in high oxidation states of metals, the alkali metal fluorides and the earth alkali metal fluorides.

That is the dangerous thing. Without you noticing it, you are destroying yourself by inhaling the fumes. Delayed effects can turn out exceedingly bad (edemia), so be careful! The more concentrated the acid gets, the hotter it gets and the more fumes are produced.

This is a big mistake. A gas has a density between 100 and 1000 times as low as the density of water. Anyway, if the concentration of the gas is so high, that an explosion occurs on ignition, then it is intensely poisonous. HCN is VERY VERY poisonous and way below the lower explosion limit, the gas already kills you within minutes. So, when the Nazi's came into the gas chambers, the concentration must have been below the ppm level (a few micrograms / liter), otherwise they would die immediately. So, the story about explosion only can be nonsense.

It does not give smell or fumes when cold, but in order to obtain 90+% H2SO4 requires heating well over 200 C of the total mix. At that temp the liquid will be heavily fuming and these fumes are exceedingly dense and corrosive.

The unreactive nature of the chloro-carborane anion indeed makes the acids so special. Ultra strong acid, without strong oxidizing or coordinating properties. All other acids also have a corrosive anion, even chloride is very corrosive under the acidic conditions in hydrochloric acid. Unfortunately I have no answer to the second question, maybe someone else. The last thing is not very likely. An acid is strong, or it is not. If the acidic action depends on the counter-compound, then one formally cannot speak of an acid anymore and other methods need to be used for describing them.

No, sulfuric acid has structure O2S(OH)2, so all four oxygens directly bonded to the S. Two oxygens have a H atom attached. There is no H atom attached to the S. The oxygens, bonded to the S, without the H on them, have a double bond, all other bonds are single.

I don't think that such a liquid exists. Anything, which is so reactive, that it reacts with air, certainly is dangerous to humans (or in fact: any life form).

If you want knowledge about practical chemistry (properties of compounds, the elements and so on), pick up an old book. Especially the pre-war books (1900 - 1940) are really great. At an antiquariate you might find some of these for just a small amount of money. Furthermore, some links on my site to good books: http://woelen.scheikunde.net/science/chem/elem/refs.html If you want to delve into quantum theory and you want to really understand it, first try to learn yourself the needed mathematics. I'm afraid that will be a really big burden for most people. The following concepts of mathemetics should be understood, before you even start thinking of delving in quantum mechanics: - partial differential equations - linear algebra: basics - linear algebra: vector spaces - linear algebra: operators, eigenvalues In quantum mechanics, most things are described by complicated partial differential equations. By assuming a certain form of the solution of these equations, they can be converted to a problem of finding eigenvalues of certain linear operators (often infinite dimensional).