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Everything posted by Flashman

  1. But it would be an efficiency issue if you can be comfortable at 19C with 30% humidity rather than 21C with 0% humidity. Then the question would be whether it costs more to maintain 30% humidity vs 2C more temperature differential with the outside walls. However, yes you can go off the other way, 80% humidity at 19C would probably tend more towards "clammy".
  2. Those pink skinned primate things that typically inhabit your typical dwelling, lose heat through evaporation of water from the skin. Since the purpose of wastefully heating this volume of air is to keep the naked primates cozy, then increasing humidity will decrease the rate at which water can be lost from their skin, thus reducing the rate of heat loss, thus making them more comfortable.
  3. So umm, you wouldn't get anywhere by centrifuging water at 1C would you? Thermal diffusion still too great?
  4. Depends how impatient you are too, the longer you wait, the more charge you get, but it never quite gets full. Like if you cross half the room, then cross half the distance remaining, then half that, then half that... you never actually get to the other wall.
  5. Hi folks, I need (I think) some zinc oxide in a hurry, I've got zinc, I can get 3% peroxide solution, how effective would that be in oxidizing zinc? Is it a grind the zinc into it and come back next week kind of thing, or needs heat, or fairly rapid at room temperature, or even not worth bothering with with that low a concentration of peroxide? Is it likely to make a precipitate that can easily be retrieved with a coffee filter or will it be too fine? Then because I only have a small strip of pure zinc, and disemboweling batteries is messy, how rapidly would 3% solution, hot or cold attack steel? I'm thinking of course of retrieving it from galvanized nails or plate. I guess if it's visibly obvious when the zinc has stopped reacting, then that might work without getting too much rust or rouge in there, but if it attacks the steel quite rapidly, then I guess I might not want to do that. Thanks for any hints, Flashman. Oh... I actually need to use it in a Sodium Hydroxide solution for a zincate coating bath... I just realised in looking up dry cell chemistry, that a Zn to ZnO process with hydroxide is used in alkaline batteries... Now, if I stick Zn and Cu electrodes in NaOH solution and allow current to flow, what copper compounds am I likely to end up with, copper hydroxide, or copper oxide? I understand the ZnO to be soluble in an NaOH solution, so should I be able to filter out the copper compounds? Or should I "bag" the copper electrode in a coffee filter, (Think permeable membrane) so I can just yank it and all the copper compounds out? Then what's a good way to determine the strength of the remaining hydroxide?
  6. It's important to realise that any ideas you might get for small scale models may not scale up. There's potential problems with mixing up fuels or reactants for example, where the amount of heat generated in a reaction can easily be dissipated from teaspoon quantities, but where mixing large amounts would boil buckets full or prematurely explode. You get any issues with incorrect reaction speed, due to propellant grain size or quality, nozzle blockage, self confinement, etc you've just taken out a city block, and they probably won't find enough of you to bury.
  7. Take one balloon, one nozzle made from a pen cap, and one plastic toy car, tape balloon to nozzle, tape nozzle to back of car, inflate balloon, enjoy.... Because I can't for the life of me imagine that you'd consider messing with the 100lb or so of highly dangerous chemicals it would take to push a real car with absolutely no experience in propellants.
  8. Benzene, no, but a shot of mineral oil to move it all through probably works good.
  9. Interesting stuff. I had a bee in my butt a while back about trying to use a thermite for making a ceramic, I can't recall exactly where I was going, hope I scribbled it on an envelope somewhere.
  10. I might have gone home, ate half a loaf of burnt toast, then put myself on 1000mg vitamin C 3 times a day... that'd take care of a lot of potentials.
  11. Thanks for pointing that out, I'm not particularly worried about corrosion at the moment. This will be something of a proof of concept thing. Not quite sure but I think the alloy involved might have a small fraction in it already. I'm reading about zincate baths to prep the aluminum, but I would rather steer clear of zinc because it has effects on the process I'm trying to achieve with the copper. The copper is required as a catalyst. The part will see heat up to around 150C but normally about 100C. I'm thinking the zinc will migrate to the surface, which would be bad, and any porosity of the surface would let the zinc get involved. This would tend to form acids, and I would have a corrosion problem. Hmmm pondering stannate baths (tin) gotta figure how the heck I would get tin or tin oxide, and whether it would mess anything up like I suspect zinc would.... wondering if food cans have any amount of tin on them still and whether I could get tin oxide by boiling them in 3% H2O2... What I seem to be seeing happening is that at .5V I can get a "tint" coating of copper attached to the aluminum, which won't rub off with a paper towel or scratch with a fingernail. However, I'm not sure but I don't seem to get much of an increase in that plating with time at .5V, it seems like it stops at some point. Therefore having got what seemed like a firm foundation, I upped voltage to 1.5 and got peeling copper foil again, leaving the aluminum clean and scratching off. This is on a test piece that has been scoured with steel wool in a sodium hydroxide solution. So is there some voltage at which it's "blowing off" the plate? Or some critical voltage where I can get it to continue plating reallllly slowly? Bugger! Just found out tin might be as bad as zinc. They both catalytically promote an oxidation reaction, which I do not want. Don't know if I can figure out which is the "least worst". I think I had it figured that zinc would only be a problem in the upper temperature range. Tin is usually in combination with something like nickel or platinum, so trying to find out what it does on it's own or in combo with copper is difficult.
  12. Thanks, I wanted to anodize something else, but been hitting a brick wall locally for getting sulphuric acid, well as battery acid anyway. I wouldn't like to think of trying to plate on top of anodizing, even if it wasn't sealed, I'd be thinking the tubes would plug early, and you wouldn't get anything like a plating on it. If I just wanted it copper colored it would probably be a better way to go. I need the copper for it's chemical properties rather than it's appearance.
  13. Whoops, you're right, not thinking rigorously, had a glitch in my mental free body diagram. Maybe should have said, the resultant displacement towards the center of mass is dependent on the velocity. At classical velocities the force remains the same, independent of the velocity.
  14. I was thinking azeotrope, and looked it up, for which I've got 35.35% as the magic number. Maybe it doesn't take long to boil down to that?
  15. Classically, the force is gonna be the same however fast it's moving, however the resultant acceleration actually affecting it would change according to it's velocity component at right angles to the gravitational force.
  16. Howdy good folks, I've gotten myself into a bit of a conundrum. I need some copper plating on an aluminum alloy surface. My chemistry is about 20 years rusty, but I understand this is meant to be "difficult" to "unpossible" with a simple CuSO4 electroplating setup. However, I remember achieving a reasonable plating on aluminum before, many years back, when I was a kid with a model train transformer and a bag of CuSO4... So, been looking around here and on the rest of the net for tips... it occurs to me that I could use some method not regarded as commercially viable, either due to time factors, or current consumed or whatever. I don't really care about the quality of the plating, in as much as it can be porous or rough or streaky or lumpy or have green and purple spots in it, as long as it stays more or less stuck to the aluminum, and is more or less a copper surface. Now, for some odd reason instead of trying to figure out exactly how I did it, I thought I'd start out with some stuff I pulled up of the web... http://chestofbooks.com/reference/Henley-s-20th-Century-Formulas-Recipes-Processes-Vol3/Plating-of-Aluminum.html ""Make a bath of cupric sulphate, 30 parts; cream of tartar, 30 parts; soda, 25 parts; water, 1,000 parts. After well scouring the objects to be coppered, immerse in the bath."" So last night I tried that, with baking soda, I was figuring with cream of tartar and either baking soda or washing soda, I'd end up with Rochelle salt, the baking soda would just make more carbon dioxide. Scrubbed a sample piece of aluminum with steel wool and dilute sodium hydroxide, rinsed it and put it straight in there, for an hour, nothing, then put it in a warm water bath, nothing... not even a hint of a tint on the darn thing... bah. I was hoping at least to get something of a strike coat (is that the right word) so I could electroplate more on top. Now I figured I may as well try some current through that solution since Rochelle salt is recommended in other electroplating recipes, so gave it about 6 volts and it fizzed merrily and gave me a peel off sheet of copper foil. So, I scrubbed it off with steel wool and NaOH again and tried again with minimum voltage, half a volt give or take, and 10 minutes gave it a tint I couldn't rub off with a paper towel, looks promising.. Giving it an hour or two at that sometime today to see what happens. Anyway, complete and abject failure of the bath in the first place had me wondering if the "soda" should have been lye. Also wondering if it should be aiming at an excess of tartaric acid or not to be a little acidic, didn't know whether proportions were by weight or volume, mixed it by volume. Still also trying to figure what "went right" when I did it so many years back, I was plating all sorts of scraps just of the hell of it, might have had a carbon anode, might have had a nail, so don't know what the hell my solution ended up containing by the time I got the aluminum in it. Could have been acidic by then with sulphuric acid due to depletion. Also used tap water, which had at the time flouride ions in it, which I've heard mentioned for plating aluminum... Anyway, what I need is some way to get some sort of copper plating on aluminum alloy with "household" chemicals, don't want to be messing around with cyanides or anything that takes 2 weeks to get hold of. Thanks for any hints about what is supposed to happen, and how to tweak things, Flashman.
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