woelen

I think that indeed it all boils down to the fact that the magnets are made of metal and the experimental outcome is not that surprising to me. There are two types of forces. We have the true magnetic force, due to the fact that both pieces are magnets, but we also have a second component, being the plain attraction of iron (or some other ferromagnetic material) to the magnets. The true magnetic force is perfectly alternating and has average value 0. The plain attraction of ferromagnetic material always is present and results in a net attraction. So, the total average force will be attracting. This is what the others also mentioned already. --------------------------------------------------------------------- The experiment would become really interesting if "ideal" magnets could be used, which only exhibit magnetic fieldlines, but do not add the effect of their material being attracted by the other magnet. Even with such magnets, I can imagine that the experimental outcome still can be very surprising. A somewhat related effect exists for electrostatic forces. Many people think that a charge distribution, which looks as follows: +-................................................................................+- does not feel any attracting forces (with the + and - charge rigidly attached to each other, and ...... representing empty space). Suppose the distance between + en - is small, relative to the length of ......, but still non-zero. Then such a system shows a net attractive force, provided the dipole objects +- are free to rotate. This net force is very small, but it nevertheless exists. It only is present as second order in the distance between the +- charges inside a dipole object. They orient themselves in a fashion as shown above. In chemistry this effect is known as "Van der Waals" force. A similar effect may be present in the experiment with the magnets, where the rotating magnet is allowed to move away from the fixed magnet or move towards it (so, translation is allowed besides rotation). The complicated motion patterns may result in a second (or even higher order) average attracting force.

Yes, I know that oxidation by transition metals is quite common. Probably I was not clear with my post, but what I meant to say is that I think that the ascorbic acid is reduced by the magnesium metal. The ascorbic acid in the test tube, with the NaOH only reduces copper (II) to copper (I), but the ascorbic acid in the test tube, with the magnesium reduces copper (II) to metallic copper. So, there is a difference in reducing power of both solutions. I have done further experimenting and ascorbic acid, treated with NaOH simply is not capable of reducing copper (II) to metallic copper. Ascorbic acid, treated with magnesium (of course, any remains of metallic magnesium being removed before copper (II) is added), reduces copper (II) to metallic copper very quickly, it only takes seconds to do so. I hope that my point is clear with this second post. What I think is very special is that ascorbic acid can be reduced.

It is well known that ascorbic acid (a.k.a. vitamin C) is a fairly good reductor and as such it is used by our body and also in many foods. In those places it acts as antioxidant, itself being oxidized, instead of the food or the material in our body. Surprisingly I have found strong evidence, however, that ascorbid acid also can act as a reductor under very "normal" conditions. I would like to have a second opinion on that. I did the following experiments: 1) Add some NaOH to an excess amount of a solution of ascorbic acid. This makes an ascorbate/ascorbic acid mix in solution: OH(-) + HAsc --> H2O + Asc(-) To this, add some copper (II) sulfate. 2) Add some metallic Mg to an excess amount of a solution of ascorbic acid. This also was supposed to make a mix of ascorbate/ascorbic acid, but now with some Mg(2+) ions in solution, instead of Na(+) ions: Mg + 2 HAsc --> H2 + Mg(2+) + 2Asc(-) To this, also add some copper (II) sulfate. In the descriptions above, HAsc is ascorbic acid, Asc(-) is ascorbate ion. In experiment (1) the copper (II) sulfate quickly is reduced to an orange/yellow suspension of hydrous copper (I) oxide. This is precisely what I expected. That is the normal mode of operation when copper (II) is reduced in mildly alkaline solution (c.f. Fehlings reagent). When some dilute HCl is added, all of the precipitate dissolves. For experiment (2) I expected the same as in experiment (1), I do not expect a major difference because of the Mg(2+). But here, a dark red/brown complex is formed, which very quickly becomes dark green and then metallic copper is separated. The liquid has a beautiful red/brown metallic lustre, when viewed with reflected light. Also, quite some hydrous copper (I) oxide is formed. When some dilute HCl is added, the copper metal does not dissolve. After standing, it forms a nice brown/red layer at the bottom. What I think is that in experiment (2) not only the reaction Mg + 2 HAsc --> H2 + Mg(2+) + 2Asc(-) occurred (which is a standard metal/acid reaction), but that a side reaction occurred, where the Mg reduces some of the HAsc to an even stronger reductor. I have been looking at the structure of ascorbic acid, but I'm not sure what the structure of this even more reducing agent could be. Is there someone out there, who could shed some light on this?

I have done a lot of experimenting last two weeks with all kinds of halates and have investigated how fast they react, when mixed in a pyrotechnic mixture. I have access to the following ones: potassium chlorate, KClO3 potassium perchlorate, KClO4 sodium perchlorate, NaClO4 potassium bromate, KBrO3 potassium iodate, KIO3 potassium metaperiodate, KIO4 sodium metaperiodate, NaIO4 Of one of these (KIO4) I have made high speed movies with a digital camera, see thread http://www.scienceforums.net/forums/showthread.php?t=20936 . What I have observed is the following order of reactiveness with red P. KBrO3 > KClO3 >> KIO4 ≈ KClO4 >> KIO3 KBrO3 is slightly more reactive than KBrO3. This is so reactive, that a mix of KBrO3 and red P cannot be made safely. The same is true for KClO3 and red P. These, however, can be mixed, but that must be done VERY carefully. In many cases the mix explodes/ignites on mixing. A mix of KBrO3 or KClO3 with red P gives an explosion when the chemicals are mixed. Both KIO4 and KClO4 can be mixed with red P without problem. I never had an unexpected explosion while mixing, so this mix is less sensitive. However, on heating, the mix explodes. This also is shown by the video, given in the other thread. With KIO3, the mix does not explode. It burns with a whoosh sound and gives purple smoke. It burns quite fast, like black powder, made of KNO3/C/S. I have also done experiments with the anhydrous sodium salts NaIO4 and NaClO4 and red P. These seem to be somewhat less reactive. This surprises me, because I expected the same effect as with KIO4 and KClO4. NaClO4 is somewhat hygroscopic, but NaIO4 certainly is not. Apparently, the ions are attached somewhat stronger to the (smaller) sodium ions. Still, with these, an explosion can be obtained. With sulphur, KBrO3 is very violent. It does not explode, but gives a very bright white flame and it burns very fast. With KClO3, the mix also burns very fast. With KIO4 and KClO4 the mix burns, but I had some difficulty igniting it. It is much less sensitive than the same mix with KBrO3 and KClO3. A mix of KIO3 and S hardly can be called a pyrotechnic mixture anymore. These are interesting observations. Are there any others, with similar observation with other oxidizers and/or other reductors. It would be nice to have a kind of roundup on many oxidizer/reductor combinations. I also noticed that for the red P mixes somewhat larger quantities (still only 10 ... 15 mg of mix) usually result in a high-pitched loud explosion, even when the powder is not confined, while at lower quantities there is a kind of low WHOOSH sound, close to explosion, but not as nearly as loud as the high-pitched explosion. Appaently, even unconfined powders can exhibit a form of self-confinement. Is this because the reaction proceeds faster, than that the gasses/smoke can be expelled from the mix? If someone wants to repeat these experiments, please be careful and do not use quantities larger than 25 mg or so. With 25 mg the bang can be very loud already and the flash of fire can be really hot. So, be careful, especially when mixing the chems. Never mix larger quantities at once, limit the mixing to quantities of 25 mg total stoichiometric mix.

That crystal could indeed be a nice crystal of benzoic acid, but it also could be K2SO4. K2SO4 is only sparingly soluble and easily forms nice glassy crystals. It the aqueous layer of the first synth completely colorless now? If that is the case, then you know that all permanganate is oxidized completely. Benzoic acid is almost insoluble in water, but I do not know its solubility in toluene. You could take out a drop of the toluene layer and let it evaporate. It might be that you get many small crystals. If you don't, then that means that most of the benzoic acid is in the aqueous layer, and then indeed I expect the large crystal to be benzoic acid.

I agree with gcol, but also with insane_alien. If diamond indeed turns to graphite in thousands or even millions of years, then it is thermodynamically unstable and then the graphite indeed is more durable on the (VERY) long run. I do not think this is of any practical concern, but theoretically it is important. It is known that KClO3 also is thermodynamically unstable and that it disproportionates to KCl and KClO4. This reaction indeed occurs on heating of KClO3, but at room temperature this reaction is so very very slow, that KClO3 can be stored for thousands of years with only very slight or even no measurable contamination of the compound with KCl and KClO4. Probably gcol found a similar thing on diamond. Insane_alien also is right. Graphite has a (somewhat) lower potential energy and hence more energy is contained in the diamond lattice. Burning of diamond then indeed produces more energy. Also that is of no practical concern, because of the very slow reaction of diamond, but theoretically there is a point.

Ah, what you observed indeed was the green manganate. It is not dangerous at all. Probably the concentration of KOH was not that high, that the permanganate already decomposed spontaneously. However, with a reductor as MB, even at moderate alkalinity, the permanganate is reduced to manganate (and then no gas can be observed), and finally, the reduction proceeds further to the brown MnO2. What is the color of the crystal? Is it white/transparent, or does it have brown spots in it? That crystal most likely is potassium benzoate in your alkaline liquid. However, it also could be just K2CO3, because of absorbtion of CO2 from the air by the alkaline solution. If you add acid to a small quantity of the aqueous layer, and the solution starts bubbling a lot, then it has absorbed a lot of CO2 from the air. I usually do longer-lasting experiments with alkaline solutions in well-stoppered test tubes or bottles, otherwise within a few days, all hydroxide is converted to carbonate.

Yes, permanganate in alkaline solution is capable of oxidizing quite some aryl-compounds, but unfortunately, the permanganate itself only is reduced to MnO2 and not further. This means that 40% of the total oxidizing potential of the permanganate is not used and that is a pity. In alkaline media, the oxidation state of manganese goes from +7 to +4 and in acidic media, the oxidation state goes from +7 to +2. There also is a side effect, being that permanganate is not really stable at very high pH. Part of it is converted to manganate, which contains manganese in the +6 oxidation state. That goes to +4 and then only 2 electrons per manganate ion are available for oxidation and a side product is oxygen, which escapes into the air. So, effectively, only appr. 50% of the oxidizing power of permanganate is used in alkaline media. YT, if you want to see that nice manganate effect, then make a concentrated solution of NaOH or KOH (doesn't matter which one), and add a single crystal of permanganate to this. The liquid will turn deep green instead of purple. That green color is the color of manganate ion, MnO4(2-). If you observe very carefully, then you also may see tiny bubbles of oxygen, but the dark solution may make that observation difficult. Here follows a page with properties of manganese. Look at the section on oxidation state +6 for the manganate. http://woelen.scheikunde.net/science/chem/solutions/mn.html This manganate looks neat, but its formation is not good in oxidation experiments, because it causes a loss of 20% of the oxidizing power of the permanganate.

I think that ligroin, naphta or a solvent like white spirit can do the job for you. To get rid of the final thin coating, scrubbing with hot water and soap should be OK.

Please use normal spelling, punctuation, and grammar!! Take a little more time to write down your posts.

If you have solid NaBH4, then you can make B2H6 by adding the solid to almost pure H3PO4. With conc. HCl the B2H6 is hydrolysed by the water in the acid. If you have 85% H3PO4, then boil it a little to get rid of most of the water, and then add NaBH4. Yield is not 100%, but sufficiently good to obtain reasonable amounts of B2H6. Btw, the bonding mechanism of B2H6 is very interesting. It has structure H2B-(μ-H)2-BH2 Here, the H-atoms are bridging between the two boron atoms. These H-atoms use a special bond-type, in which 3 atoms are involved, which together share 2 electrons. The B-H-B bonds are 3-centered 2-electron bonds, one electron donated by the H atom, and one electron donated by one of the boron atoms. In this way, three atoms share 2 electrons and by doing so, both boron atoms have 8 electrons and all hydrogen atoms have 2 electrons. The H2B and BH2 units are builtup by ordinary B-H bonds, each donating one electron.

Well, I'm Dutch, but the words "pondus hydrogenii" definitely are no Dutch words . It seems like Latin to me. The word "pondus" does not mean anything to me, the word "hydrogenii" means something like "of hydrogen". EDIT: I have done a lookup and the word "pondus" means "pressure".

I really like modern classical music with quite some mystique in it and sometimes just raw crying out of one's fears, sadness, and angers. Some names: John Tavener Arvo Pärt Henry Górecky Lili Boulanger

The combination of baking soda and vinegar also is a very nice one. A lot of bubbling and formation of foam. Especially if combined with some food dye-stuff, you can make beautifully colored foam. With some creative molding of soft paper you can make nice volcano models, which really spew out "lava". Fun, and absolutely without risk. Another nice one is red cabbage. You can make many colors: With washing soda: yellow With dilute ammonia: green With dish washing soap: purple/blue With vinegar: pink/red (With hydrochloric acid: deep red, but this is not the plain simple kitchen stuff for most people). Yet another nice one is the production of a deep blue copper solution by immersing copper wire in a solution of dilute household ammonia (~5% NH3), while allowing contact with air. With vitamin C this solution can be turned in a colorless liquid, which becomes blue at the surface on standing and colorless on shaking again.

Magnesium sulfate in fact is not such an interesting chemical. You can do some precipitation experiments, but that's all. You indeed can use it as a fairly powerful drying agent, when it is calcined and the crystal-water is removed from the chemical. As YT suggested, it also is used as fertilizer. In certain pyrotechnic compositions it also is used as a high-temperature oxidizer, but that is very hard to ignite. I have understood that it can be used sometimes for white flares, but I must admit I'm not a fireworks expert, so someone else may jump in to give more info on that.

Yes, I also noticed they have MANY websites. This is a strategy used by more companies. Using so many websites, each emphasizing on a different chemical, there is a bigger chance that a google search gives hits to their pages. But all these sites are from the single company http://www.kno3.com.

I have my carbon rods from batteries, but from a special type. These batteries contain long rods (8 ... 9 cm) with a diameter of 8 mm. The standard AA cells, A cells and so on, contain very small rods. The battery, I am referring to, has 4 of these rods, internally it contains 4 cells, each cell delivering 1.5 V of output voltage. http://www.apexbattery.com/accessories-6-volt-lantern-battery-miscellaneous.html These types of batteries provide an affordable and easy to obtain source of large graphite rods. It only takes an hour of (dirty!!!) and careful work to get these rods out of the battery.

Clearing that acid will be (almost) impossible. Due to its high viscosity and high density, the particles will not sink to the bottom, so letting it stand for a long time will not help. Filtering will also be very difficult, due to the viscosity, and also due to its corrosiveness. Strange that your drain cleaner is so terrible. Apparently it depends on where you live, how it looks like. Over here, draincleaner is 97% H2SO4, and it is almost colorless (pale brown). But, I've heard from other people that it indeed also can look like spent motor oil.

Yes, and that is with very good reason!

It might be that some of the sweet compounds in honey are broken down somewhat (hydrolysis?) in hot water. Another thing may be that boiled water contains less impurities (air/oxygen is driven out, calcium bicarbonate is partly precipitated as calcium carbonate). Although these are just subtle effects, it might be that it does affect the taste considerably. The human sense of taste is very sensitive to changes. But, I must admit, these are just my thinkings about the subject. Maybe someone with more knowledge about the precise composition of honey can give more insights.

YT, now it IS time to take some action. You have waited long enough!

On their site they write that they sell only to companies, but that probably only is on their site to keep officials, asking difficult questions, away from them . In reality they sell to individuals as well. They introduced themselves at the sciencemadness forums and at sci.chem and there they offered chemicals to everyone. Because of that, I decided to contact them and indeed, they sell to individuals. No company who only sells to official businesses would introduce itself at sci.chem and sciencemadness. Those are the places for chemistry hobbyists. They only want to know whether you are an adult person or not. So, you certainly should contact them and see what is possible.

I have 25 grams of NaBH4 (purchased it from a photography chemical supplier), and it is used as a reductor for those purposes. It is also used in organic chemistry as a more selective/less destructive reductor than LiAlH4. It is really striking to me, however, how stable NaBH4 is in water. In DMSO it gives rise to extremely smelly sulphurous compounds (I tried it ), probably due to reduction of the DMSO to (CH3)2S, but I'm not sure about that. I only noticed the smell, I did not find any details about that reaction though. Furthermore, I use NaBH4 mainly for keeping very air-sensitive precipitates, such as Mn(OH)2, and Fe(OH)2 good for a somewhat longer time. With just a very small pinch of NaBH4, dissolved in water, I can do experiments with air-sensitive materials which I otherwise could not do. The NaBH4 protects these compounds, byt taking away the oxygen.

Alt_f13 raises a valid point about conservation of momentum. So, I agree with his answer. The situation where the ball bounces back implies a negative impulse for the ball, so the momentum will be larger for the car in the bounce-back situation. However, the example alt_f13 supplied is not really correct. There also is conservation of energy. In his example the ball bounces back with the same speed as it had before, so the kinetic energy of the ball would be the same as before. Besides that, the car moves forward and that also has a certain energy. So, the speed of the ball bouncing back will always be smaller than the speed at which it was moving towards the car before impact. The whole concept of conservation of momentum only is true in ideal collisions with colliding objects having no friction-coupling with an external reference frame. The following example can make things clear: Suppose the car is fixed to the ground by means of a big pin. It cannot move at all. You may also replace the car by a thick rigid wall. Now, if the ball is moving towards the wall, it bounces back. Still, we have conservation of energy, but do we also still have conservation of momentum??? From a practical point of view we would say no. Momentum is reversed. But now looking at it completely theoretically, we still can say yes. Assume that we have two free frictionless objects with mass M1 and mass M2. M1 is the ball, M2 is the car. Now, if we increases mass M2, then we'll see that total momentum remains the same, but because M2 becomes larger, its speed becomes lower and lower. When M2 approaches infinity (the situation of a big rigid wall, attached to a fixed world), then impulse still is conserved, but the part imposed on M2 does not show up anymore, because its speed goes to 0, as M2 goes to infinity. So, purely theoretically, we still have conservation of momentum.

What do you count as boranes. Do you only call compounds BxHy borane, or do you also include ions like BH4(-) as borane. There are some ionic B/H compounds, which are quite stable. NaBH4 is decomposed by water, but that reaction is quite slow. In practice, one can have solution of this salt in water for quite some time. I have tried to isolate BH3 (B2H6, IIRC, H3BBH3 is a better representation) by adding acid to a solution of NaBH4, but that does only yield hydrogen. Apparently, borane molecules are quite unstable in the presence of water. Boranes are quite strong reductors. The sodium borohydride is probably the strongest water-soluble reductor I have, but it is not capable of reducing chromium ions to the +2 oxidation state, nor is it capable of reducing vanadyl ions to vanadium in the +2 or +3 oxidation state. For those reductions in aqueous media, I need powdered zinc.