woelen

Yep, this is also what I would say. Suppose the plain is standing still on the belt and the belt starts moving. Then the plain will not move together with the belt, the wheels will rotate and the plain will remain on its place, fixed, relative to earth. When the plain starts its engines, then it moves just as if it is on a normal air-strip. The only difference is that the rotational speed of the wheels is different. Of course, if there is friction in the wheels, then things will be different. Then the plain will follow the belt and then for each force, applied by the plane's engine, there will be a velocity, such that the engine's force is neutralized.

This looks a lot like the cotton wadding experiment I did some time ago, but using sheets of paper of course is nicer. There is only one concern. How stable are these pieces of paper on storage? On a dutch chemistry forum I read from a person that these nitrated papers and pieces of wadding can self-ignite if not carefully prepared. He could not tell though what is meant with 'carefully prepared'. Just to err on the safe side, I would store them in a metal tin, which is loosely capped. If they ignite, then the tin will keep the fire confined. A plastic box will melt and may also catch fire. I'm gonna try this. This would be nice for tomorrow evening

Two different religions of woman and man? The devil sleeps between them! To my opinion the biggest mistake was made years ago, when the two were married. I've seen too much misery about this and I sometimes still see it happen. You and your wife have to find a way to solve this problem. If you and your wife will not be able to solve this (futile?) issue, then what value has your marriage then anyway?

I did isolate iodine by taking a beaker and putting in the slurry of iodine/water/acid remains. I put a glass plate on top of the beaker and then heated it. The crystals of iodine quickly settle at the glass plate, together with some water droplets. Then I took the iodine with water droplets from the glass plate (and also the walls of the beaker) and mixed this with some conc. H2SO4. This binds the water and then again repeat the procedure. This way, you get rid of most of the water. A third time gives you totally dry iodine. Commercial iodine is triple distilled. Another way of isolating the iodine is dissolving it in some solvent (e.g. low-boiling ligroin) in which water does not dissolve. I'm not sure though how well iodine dissolves in the ligroin. A better solvent would be CS2, but that is very toxic, very stinky and not easy to obtain. It also adds some impurity to the iodine. I myself did not try the extraction procedure. The distillation procedure worked fairly well for me.

No NBr3 is formed in this experiment. NBr3 is not known at room temperature. I have read that it only can exist at ultralow temperatures and even then it only has fleeting existence. This experiment is perfectly safe to perform (as far as explosion risk is concerned), the main risk is the bromine vapor, but even that is not a real issue, if done in a well-ventilated room (only 100 mg or so is used). Ammonium bromide is non-toxic, practically speaking, but of course you should not eat it. Iron nails also are non-toxic but when you eat them, then you'll have a bad feeling afterwards, it is the same with most non-toxic chemicals. Over here in NL, ammonium chloride also is used a lot in sweets. It is sold in the pure state as a white crystalline solid under the name 'salmiak'.

Yet another experiment I want to share with you. I made some very nice crystals with a dendritic structure. These are easy to make: http://woelen.scheikunde.net/science/chem/exps/crystals/index.html Keep in mind that the used chemical (ammonium chromate, or ammonium dichromate + ammonia) most likely is a carcinogen. Avoid inhalation of fine dust!

This is a cool experiment I did with ammonia and bromine vapor. The reagents for this experiment are very easy to obtain or to make: http://woelen.scheikunde.net/science/chem/exps/NH3+Br2/index.html Bromine vapor can easily be made if you have a bromide (which can be purchased without problem). If you repeat this experiment, be careful with the bromine vapor, that vapor is very toxic. Follow the safety warnings on the webpage.

What equipment are you referring at. Simply take a plastic tray, or a glass oven-scale and put your PCB in that, together with the etching liquid. Using vinegar might work, but it will be painfully slow (days???).

SbCl3 cannot exist in water. It is hydrolysed and a basic chloride is precipitated, or even an oxychloride is precipitated: SbCl3 + 2H2O ---> SbCl(OH)2 + 2H(+) + 2Cl(-) SbCl(OH)2 ---> SbOCl + H2O SbOCl is insoluble

I don't see how NaCN can be formed from molten NaOH, when a C-electrode is used. Where does the N come from?

YT, did you really add HCl to the chlorate cell? That is absolutely not good. It prevents formation of chlorate, because the reaction of making chlorate requires hydroxide. Adding dichromate to the cell is a good thing, but removing it is really hard, if you use carbon rods for the anode. I have found out that the carbon anode gives off tiny particles of carbon, which adsorb some chromate and/or chromium(III). These carbon particles are so small that they cannot be removed easily. If you, on the other hand, use a platinum anode (and the cathode can be any metal), then the product is really clean, and also remarkably, the chromate can be removed VERY easily. It simply does not get included in the crystal lattice of the halate formed. So, it is the combination of carbon and dichromate, which makes such a mess.

If you dilute a solution with dissolved NOx gasses, then it becomes colorless at once. So, your blue color really is due to copper ions. Just a check you could do: Take half a ml or so of your solution and add 5% household ammonia to this, until the liquid becomes clear again. If this liquid has a fairly strong royal blue color, then indeed you have copper in your solution. If you have done this test, please do not store the liquid with ammonia. Either neutralize again with acid, or get rid of the liquid, but don't store it. Silver/ammonia complex slowly forms an explosive compound (fulminating silver).

I also wish all of you a very good Christmas and a pleasant holiday period! And for all of you, playing with fireworks, make sure that also in 2007 you still have all your limbs attached .

One day you will regret what you say here.... YOU could know better.

The use of complex numbers is a tool. The tool helps us to solve many physical problems, but it does not make the numbers more real. The example I gave for electronic circuits is a nice demonstration of this. None of the voltages and currents in the circuit really is complex or imaginary, they all are real. But, the use of euler's formula (exp(ix) = cos(x) + i sin(x)), combined with the use of properties of linearity can be used to solve many problems in a very elegant and compact way. You will also notice that in non-linear physics the use of complex numbers is much more limited, unless the non-linear system is regarded as an infinite dimensional linear system. But the latter approach in many cases is just as cumbersome as the direct non-linear approach.

No, none of the expressions will become negative. The minus-sign is not there to prevent the expression from becoming negative, it reflects the consumption of A and B. The concentration of either A or B will go to 0 asymptotically (the one with the lowest initial concentration) at an exponential rate. Have a look at the equation dx/dt = -kx. It will go to 0 as x(t) = x(0)*exp(-kt), where x(0) is the initial value of x and x(t) is the value of x at time t. Of course, the model of the reaction is more complicated, but qualitatively, the model has similar behavior for the compound with lowest initial concentration.

As I said, what I wrote down still is highly simplified. You are right, but not entirely 100%. What happens in reality is that water-ligands are replaced by chloride ligands. So, you will get ions [ce]Cu(H_2O)_3Cl^{+}[/ce], [ce]Cu(H_2O)_2Cl_2[/ce], [ce]Cu(H_2O)Cl_3^{-}[/ce] and of course [ce]CuCl_4^{2-}[/ce]. At low pH, also H(+) ions can be coordinated to the complex, making the situation even more complicated.

I agree with encipher. Davy was a researcher, who spent a lot of time and money on this subject. The average home chemist does not have the equipment and the skills to do so. There may be some home chemists, who do have the right equipment and skills (there are a few, active on http://www.sciencemadness.org), but I do not count myself to those persons who could safely make Na from molten salts and isolate it. Really, if you value your health, please do not attempt to do this kind of reaction, unless you REALLY know what you are doing and have very good equipment.

It depends on what your x is. If x = [A] or x = , then you indeed have a negative sign, but if x = [C] or x = [D], then you have the positive sign. This can easily be explained. The rate of reaction in this case is k*[A]* for some positive constant k. But while this reaction is running, compounds A and B are consumed, while at the same time compounds C and D are produced. So, the concentration of [A] and decreases, and the rate at which this happens is k*[A]*. so, d[A]/dt = -k*[A]*, and the same is true for d/dt. The concentration of [C] and [D] increases, and hence a positive sign is used for these: d[C]/dt = k*[A]*. If you were going to solve these differential equations, then you'll see that the concentration of [A] and decreases, but the reaction goes slower and slower. At the same time [C] and [D] increase, but the rate at which this happens also is slower and slower.

This reaction eqation is not what happens. You can only describe this reaction in terms of ions and then you'll see that only very small amounts of H2SO4 will be formed. CuSO4 dissolves in hydrochloric acid as follows (and even this is strongly simplified): CuSO4(s) + 4Cl(-) + H(+) ---> CuCl4(2-) + HSO4(-) From this you will see many equilibrium reactions, leading to small quantities of H2SO4, SO4(2-), HCuCl4(-) The complex CuCl4(2-) is green.

This is fairly basic math. In fact, if you sum up powers of i, with i ranging from 1 to n, then you'll see that summing a k-th power yields a number of k+1th power (plus some correction terms of lower power). This can be connected to integrating functions. If you take the integral of x^k, then the result has power k+1. In your case, you can connect it to integrating x, which gives an expression of order x^2.

I agree with John Cuthber, that reaction of NaHCO3 never can proceed like this. What is possible though is the following: 2NaHCO3 --> H2O + CO2 + Na2CO3 It can nicely be observed by dissolving some NaHCO3 in water and then heating. The solution will loose lots of small bubbles of CO2. It is actually quite nice to see this reaction proceed. As if the water is boiling with very fine bubbles. This reaction also happens when the solid is heated.

Depends on the country where you are living. Indeed, in some countries (e.g. UK) nitric acid is sold as pH down, IIRC at concentrations of 38%. Over here in NL, nitric acid is sold OTC at 52% concentration.

It is the easiest way, if you have nitric acid. But that acid is not that easy to get your hands on in many places of the world. Another good way is to mix it with excess ammonium nitrate (from fertilizer) and gently heat. Ammonia, carboin dioxide, and water are driven off, strontium nitrate remains behind. A single recrystallize then purifies the strontium nitrate. Ammonium nitrate dissolves in water MUCH better, so they are easy to separate. Ammonium nitrate can be made from the impure fertilizer, containing 75% NH4NO3 and chalk, simply by dissolving all and letting all insoluble stuff settle.

You don't make iron chlorate! You make iron(III) chloride. It indeed is true that acetic acid liberates HOCl from the hypochlorite: CH3COOH + ClO(-) ---> CH3COO(-) + HOCl The HOCl then in turn reacts with chloride and another molecule of acetic acid to form Cl2: CH3COOH + Cl(-) + HOCl ---> CH3COO(-) + H2O + Cl2 These reactions, however, are very incomplete, because acetic acid itself also is a weak acid (but not as weak as HOCl). You certainly won't see strong bubbling of Cl2, but you definitely will smell it.