|MadSci Network: Chemistry|
Dear User, Before I try to answer your question, I would like to ask you if you have made out your last will yet ? If not, would you include me to receive whatever's left of your worldly wealth after all the medical stuff and the funeral have been paid for ? Seriously now. You "... intend to build a few and test them to see if the thrust is adequate." In such case I seriously advise you to get a good look at your family and friends. Also try to see a few good sunsets and don't forget to watch those favorite movies again. Why ? Because most likely what you're planning to do will leave you blind, and horribly burned. The chemistry of the reaction is simple: 2Na + 2H2O -> H2 + 2NaOH + lots of heat. At school, at least in my days, there was a common demonstration -- a small (pea-sized usually) piece of sodium was dropped into a large beaker of water. You might have had such a demonstration. The heat is most often enough to ignite the hydrogen, sometimes with a violent "pop" which usually sends droplets of molten, burning sodium through the air. Now, imagine the same experiment only magnified. Myself, I do not have to imagine. As a student, I used to work for the institute of organic chemistry, which was located in my city (this was, by the way, Kiev, Ukraine). Since USSR was in many respects less complicated in the areas of say, hazardous waste disposal, we were often told to dispose of old chunks of alkali metals. Of course, being curious, we could not resist dumping some of them into the nearby lake. (The lake was so polluted that nothing really lived there anyways). Trust me, a kilogram of sodium in the water is *not* what you want to be in close proximity of. The explosions are very violent, furthermore, pieces of sodium fly through the air quite far and land in water again, causing a wave of secondary fires and explosions. Very pretty, and very deadly. Now, what you are planning to do, basically, is to enclose a piece of sodium in some kind of flotation device. Sodium is considerably lighter than water, so you'd have to weigh the device accordingly. If you are lucky, it would explode instantly upon being lowered into the watrer. This would save you these long, painful days in the hospital, and long dark years afterwards. It would also save your relatives from having to deal with a blind (and horribly burnt) person for the rest of their lives. They would only have to deal with you being dead, which is painful but brief compared to a life of misery. If you are not lucky, and the device actually floats for a while, before igniting, then the following picture comes to mind : At first, only a little bit of water would reach the metal. It would react instantly, producing heat, gas and water aerosol saturated with liquified and molten NaOH and Na2O. This stream will jet out of the engine nozzle and spray the shore. Then, as more water comes in, the sodium will melt and flow out through your nozzle. This is the *fun* part ! The sight is very pretty. Most marvellous water fireworks are sometimes done by letting molten burning sodium or phosphorous fall through the air. The tricky part is to make sure it does not hit anyone or anything. A globule of molten sodium can and will eat through flesh, leaving a bleeding, charred hole with lots of secondary lacerations and chemical burns. The shock may kill you, or then, it may not. Also imagine your body getting a healthy dose of alkali... Blood curdling, in a very literal sort of way. Pathologoanatomers would bring their students to look at your corpse. They would call it "a learning experience". Back to our show : As soon as sodium leaks out, your engine will sink, and the sodium would jet out, burning merrily as soon as it is in the air. A sight to delight (briefly) passers-by, fish and scooba divers. At this point, you are most likely already agonizing on the shore, or in the whatever boat you might use to conduct your experiments. Interesting fact about alkali in the eyes is that if you get a lot of it in the eye at once you do not have time to do anything, you just go blind (and it is very painful too, as far as I know). Now, if you get a little, you may not notice it until it is too late (unlike acid, lye in small amounts does not hurt initially). So, even if you are super-lucky and you evade the first jet of lye or the second jet of burning metal you still have a goodly chance to get blind. Well, More or less, that's it. Oh no, not really ! There is still the part where you manufacture the sodium. It may be done of course, and indeed sodium can be manufactured from NaCl though NaCl melts too high to use it pure. Industrially, NaCl is often used in mixtres with other things. The tricky part is to conduct the melting and electrolysis in an inert atmosphere, and in such manner that chlorine and sodium are produced on the separate ends of the apparatus (preferrably several meters away, at least) and that they NEVER EVER SEE EACH OTHER. Do I need to elaborate on what happens when molten sodium meets hot chlorine ? In general, it is probably far safer to go play football on a mine field, really. There is one good thing about the whole business though. No chemical supplier in their sane mind would sell you sodium. It is, I beleive, illegal. Moreover if you injure yourself or other people with it they would be in a lot of trouble. Normally, it is impossible to manufacture sodium efficiently at home. So, at worst you will get badly burnt trying to do it (I used to know several kids who did it and were burnt). As to the H3O+ part -- well this is all theoretical work still. Solid hydroxonium belongs (yet) more to the science fiction than to practical science. Even if it was available, I doubt that you can make it at home. Diamond anvils would be a little bit too costly, and cubic zirconium is not a good substitute. As a final word, I would like to say that your enthusiasm and imagination are very nice and very valuable. All you need to do is to make sure that you have sufficient theoretical and practical basis to support these fine qualities. Cheers, and in case you decide to try these engines out, remember to write the will, otherwise your evil relative may sue the leftover diamond anvils off your giref-stricken family. A.G. Evdokimov
Try the links in the MadSci Library for more information on Chemistry.