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Posts posted by woelen

  1. In this experiment, I made some chromyl chloride, a very volatile compound of chromium, which forms an orange/brown gas. It is really weird, thinking of this vapor being a metal-compound!


    This stuff has some very interesting properties. Have a look at the page, I made about this compound:




    The chemicals, needed for this experiment, are quite common, and I expect that many people, who read this and who do some serious home chemistry, can easily repeat this experiment.


    Be careful though, chromyl chloride is a carcinogen. Avoid breathing any of the vapor.

  2. For each 100 grams of BaCO3 I would take just under 70 ml of concentrated (65%) nitric acid. You need to dilute the acid before adding it to the BaCO3. Dilute the acid 5 times and then add it to the BaCO3, and heat the liquid, until fizzling stops.


    If you use acid of 40% concentration, then you need approximately 120 ml for 100 grams of BaCO3, diluted three times.

  3. Did you really buy it for that price? I have the feeling that you just are teasing a little bit. KNO3 is not as easy to find as you suggest. In many countries (including the one where I live), there simply is no fertilizer which is made of almost pure KNO3, and I also think that this is the case for the USA in many places.

  4. I assume you want to do some home chemistry? What you can obtain strongly depends on the country you live in.


    Glassware should not be a problem, just look around at eBay and search for items like 'beaker', 'erlenmeyer', 'test tubes' and plenty of stuff shows up. Usually the same sellers then also have more advanced glassware, like distilling setups, all kinds of more exotic flasks, etc. Always have the glassware sent with insurance. Sometimes the material arrives broken, especially for the larger items. If you just want some test tubes, small beakers and some erlenmeyers, then the risk of breaking is less severe. Keep in mind that in some USA states (IIRC Texas) glassware is forbidden without proper registration. Yes, this is really retarded, but it is true. So, before buying things, check out what legal implication the possession of glassware might have.


    Finding chemicals can be anywhere from very simple to very difficult. If you are a starter, then getting started with basic chemicals is not hard at all. Hardware stores have acids like HCl, H2SO4 and stuff like NH3, NaOH, acetone, ligroin.

    Metal salts can be obtained at ceramics stores, where they carry all kinds of glazing pigments. In this way, I received salts of Ni, Cu, Cr, Co, Mo, V, Fe, Zn. Ebay also is your friend with this, e.g. look at something like 'copper sulfate', 'nickel chloride', and you will find suitable sellers.

    Finding the more dangerous chemicals (strong oxidizers, fine metal powders, certain organics) is much more difficult. Over the years, I have found sources for these, but if you are a starter, then I first would stick to the more basic materials.


    Also have a read of my webpage on starting a home lab:



  5. This thread is totally screwed up. My post appears three times :confused: and even before your post with the question about making NbCl5.

    Yesterday I had troubles posting in this thread. I obtained a strange error, telling me something about clock skew or something like that (don't remember precisely).


    Anyway, my post was meant as a response to your post on making NbCl5.

  6. If you don't have HNO3, you could also try with NH4NO3. This is available as fertilizer and as coolpack. If you use the fertilizer, then first dissolve all solid, and let the insoluble crap settle. The fertilizer is not pure NH4NO3, it contains 20% or so of chalk (dolomite).


    The NH4NO3 then can be dried (just let it air-evaporate in a large dish), until you have a wet paste. This wet paste must be THOROUGHLY mixed with EXCESS of the barium carbonate and gently heated. This will give off lots of ammonia, do this process outside. Continue heating, until no more ammonia is formed. Then dissolve all of the wet paste in water and let all solid stuff settle. Keep the clear liquid and dispose of the solid stuff. The clear liquid can be evaporated and what remains is quite pure Ba(NO3)2.

  7. Making NbCl5 is not easy at all. I purchased this from an eBay seller.


    IIRC, it is made by heating NbO2 (which is quite inert) with CCl4, in the excess of chlorine. This process gives COCl2 (phosgene), together with NbCl4, which is oxidized to NbCl5 by the excess of chlorine.

    NbCl5 is VERY reactive, it is hydrolysed at once, as soon as it comes in contact with water.

  8. Making NbCl5 is not easy at all. I purchased this from an eBay seller.


    IIRC, it is made by heating NbO2 (which is quite inert) with CCl4, in the excess of chlorine. This process gives COCl2 (phosgene), together with NbCl4, which is oxidized to NbCl5 by the excess of chlorine.

    NbCl5 is VERY reactive, it is hydrolysed at once, as soon as it comes in contact with water.

  9. Making NbCl5 is not easy at all. I purchased this from an eBay seller.


    IIRC, it is made by heating NbO2 (which is quite inert) with CCl4, in the excess of chlorine. This process gives COCl2 (phosgene), together with NbCl4, which is oxidized to NbCl5 by the excess of chlorine.

    NbCl5 is VERY reactive, it is hydrolysed at once, as soon as it comes in contact with water.

  10. I don't think you are correct. The terms, as you use them give me the impression that the behavior is simply negative exponential, first order. Only the concentration of N2O5 matters, this is not an equilibrium reaction with low-rate back and forward reactions:


    Question 1:


    d[N2O5]/dt = -k * [N2O5], where k = 6.82*10^(-3)


    Question 2:


    You need to solve the rate equation, as given in question 1. The solution of this is


    [N2O5](t) = [N2O5](0) * exp(-t*k), Here [N2O5](t) is the concentration of N2O5 at time t, and [N2O5](0) is the initial concentration. With exp() I mean the exponential function.


    Now you want to determine the half life, when the initial concentration is 0.0125 M. Because this is a linear equation, half life does not depend on initial concentration. You simply have to determine the time t, for which exp(-k*t) = 0.5.


    This is the case for k*t = ln(2) --> t = ln(2) / k = 101.6 (s)


    Question 3:


    2.5 minutes is 150 seconds. So, using the solution of the equation, given in question (2), one finds

    [N2O5](150) = [N2O5](0)*exp(-150*0.00682) = 0.0125*exp(-1.023) = 0.00449 M

  11. There is nothing special with H2SO4 and its exothermic reaction with water. Many compounds have such an exothermic reaction.


    Sulphuric acid breaks down in ions and the ions are solvated (surrounded by water molecules). Thbis breaking down and subsequent solvation releases a lot of energy:


    H2SO4 ---> H(+) + HSO4(-) + energy (all ions are solvated)


    There are more compounds which do this. A funny example, which I once experienced is the gas HCl:


    HCl ----> H(+) + Cl(-) (again, ions are solvated)


    I once made some HCl-gas and some of this was blowing along my hand (which was a little humid, due to hot summer weather). While the gas was going along my hand, I actually felt the breeze and at the same time I felt my hand heating up. Very strange effect. Of course, I quickly rinsed my hand immediately when this happened, and there were no bad effects at all.

  12. You could try dissolving a mix of an iron (II) salt and an iorn (III) salt (e.g. iron (III) chloride and iron (II) sulphate). Then add sodium hydroxide to this. A dark precipitate of hydrous Fe3O4 is formed. Then boil the liquid for a while in order to make the precipitate more solid and easier to separate.


    The isolated precipitate should be washed with water and then heated to dryness.

  13. H2SO4 indeed is a very good drain cleaner, but it does not dissolve any organic compound with oxygen in it. Some plastics also may contain oxygen atoms, still they can withstand the sulphuric acid. Also, ethers withstand the acid. The acid most likely attacks the hydrocarbon types, such as in sugars, cellulose, etc. It also attacks peptide structures, hydrolysing them and breaking down the large chains. These two properties cause it to breakdown most troublesome stuff, which usually is in drains (remnants of hair, tissue, fibers).

  14. Before the use of advanced electronic equipment, determination of empiric formula's of compounds was a real art.


    Determining the ratio of C, H, O and N in organic compounds was done by completely burning the compound, such that only gaseous compounds remained. The burning was done VERY precisely, taking into account all oxygen which was added, and measuring the weight of all combustion products (water was captured first with P4O10 or H2SO4, then CO2 was captured with NaOH-solution, the remains were nitrogen, or simply 'other'). With some basic math, they could determine the ratio of C, H, O and 'other'. A compound like C6H12O6 would end up like CH2O, benzene was CH.


    The next step of determining the precise molecular net-formula was even trickier. It depended on the nature of the compound. It could be dissolved, and the drop in freezing temperature of the solution was a measure for the concentration of molecules. E.g. 1 gram of C6H12O6 gives a 6 times as low a concentration (and lower drop of freezing point) as 1 gram of CH2O. This kind of experiment was very tedious and required a lot of patience.


    Another way of determining net molecular weights was by evaporating the compound (if possible) and measuring the density of the gas at a known temperature. In this way it was discovered that methane really was CH4 and not C2H8, and chlorine was Cl2 and not Cl, or Cl3.

  15. Ad 1) This depends on the electronic structure of the element itself. For transition metals, however, things are more diffuse, because they can exist in multiple oxidation states (zinc is an exception, however) and because they can form complexes with many things.


    Ad 2) Not all oxygens will be bonded to zinc. Calcium will not be set free in this reaction, it will also remain in the +2 oxidation state, requiring an oxygen atom. Carbon also certainly will not be set free, but at the high temperatures involved, CO2 is not likely to occur. If that would occur, then we would have simple decomposition of chalk, without oxidation of zinc. Hence the expectation of CO, CaO and ZnO.

  16. The purple color is due to formation of hydroxide at the cathode. The orange color probably is due to formation of hydrous copper (I) oxide, which is formed in a secondary reaction between material from the anode and the hydroxide from the cathode. The turning clear is not easily explained, unless the orange material precipitated. Is there any solid material at the bottom?

  17. Write down half reactions (e.g. CrO4(2-) + 8H(+) + 3e --> Cr(3+) + 4H2O) for all of the oxidizers and for the reductors, and then combine the oxidizer equation and reductor equation, such that the number of electrons is the same at both sides of the arrow.

  18. Basically, there is not a real difference in the nature of the reactions. Water also acts as acid, due to self-ionization.


    In practice, however, the difference is large. The type of reaction is very similar, but in acid the reaction proceeds at a MUCH higher rate, certainly for Mg, Al. If the water is heated, then also Mg dissolves at an appreciable rate in water, Al only reacts when very finely divided and with temperatures of several hundreds of C.


    The element S is a different story. It does not react with HCl, nor with H2O. This does not show a displacement reaction and no S(n+) ions are formed.

  19. Well, things may turn out different, than one just could say on the basis of the activities series. The latter is not really applicable in situations where solid mixtures are heated.


    I can imagine that the Zn can reduce the carbonate ion when sufficient heat is applied and if that indeed happens, I expect the following:


    Zn + CaCO3 --> ZnO + CaO + CO

  20. You ask quite a lot from the volcano model. There are a few chemical volcanos. One is based on ammonium dichromate, giving real fire, but the smoke is not real, it produces ashes of chromium (III) oxide. The volcano effect is due to the large expansion of volume.

    Another volcano is based on a viscous liquid, filled with sodium bicarbonate, and adding an acid to this. The foam strongly expands, giving rise to eruptions, if constructed well, but of course, no smoke, heat, let alone pyroclastic clouds etc.


    Another idea might be to use a computer model for volcanoes. I can imagine that such models exist, and otherwise you could try to make one from general models on fluid flows, gas flows, etc. The latter approach probably is not the easiest though if you lack the physcis and math knowledge.

  21. Dit you try yourself? If so, please tell us about your experiences. Posting just a link is not that helpful, having first-hand experiences from one of our members would be great!

  22. 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.

  23. 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.

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