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johnheritage

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  1. http://en.wikipedia.org/wiki/Hygroscopy
  2. I'm afraid I have to be the one to ask this. Why on earth would you want or need to do that? But to cut to the chase even quicker, overheated or burning plastics and elastomers tend to produce some of the most dangerous fumes you will find in everyday life. They can be either immediately toxic or that and also mutagenic / carcinogenic... so on. As an example, overheating PTFE will cause it to release hydrogen fluoride. Horrifically corrosive and a powerful calcium leach.
  3. The mention of recipes potentially puts this into a category that is much more important than general chemical storage, which is primarily concerned with whether or not the container will perish; as it implies you may be consuming the contents. If so, I would highly recommend using glass. Especially so if you will be storing high percentage alcohol or ethanol in them. You are correct to be concerned about leaching. This is of virtually no importance to most people who do chemistry at home. It is of importance when discussing absolute analytical chemistry, physics and biology. That whilst materials may not fall apart, components within them can end up as trace contaminants in the contents. In the case of plastics, there is already scientific evidence that they are not as benign as people thought not very long ago at all. As an example, hormone mimicking compounds have been found in bottled water when the container is plastic, but not glass filled from the same water source; they are coming out of the plastic and the consumer is ingesting them. I do not yet know of anything known to be a life threatening problem leaching from them, but then, the research is still being done. Rather, I would suggest it is bad practice to be doing it with a pure, volatile organic solvent like ethanol and something you should avoid. Similarly, materials involved in the production of foams and other polymers, or produced as side products, can climb the food chain. Small amounts may be released by the foam packing in furniture. These then concentrate in breast tissue, meaning girls who have been exposed to such unseen, prolonged 'leaching' of the off gassing can end up feeding their baby an enriched form of it. Despite not being particularly old, I am already finding myself more and more concerned about precisely what artificial flavours do in the containers when combined into a cocktail, what the long term implications are of the heavy, daily exposure we now subject ourselves to (which isn't the same as an acute, 'responsible' exposure to one specific element) and what happens once the shake meets the billions of metabolic opportunities within a human body. That is a system that simply hasn't been exposed to such manipulation ever before. I shall leave you with another example, that numerous fruit concentrates were removed from the shelves, not very long ago, after samples from those that had been on the shelf for a while were taken and, despite this being sure fire formulation, it was found the preservative was reacting with the other components to release benzene; the solvent so carcinogenic they won't let anyone near it now. YUM!
  4. Dichloromethane may work (paint stripper / methylene chloride), as it tends to melt a large percentage of plastics. The video may need to be sped up to make it more impressive. Dichloromethane is a suspect carcinogen, so you may want to keep it off your skin and do this outdoors depending on how it'll be spread around.
  5. In chemistry, the oxide problem is navigated by treating it with a mercury salt, like the water soluble chloride. That forms an amalgam which prevents the oxide forming as the aluminium takes part in the subsequent reaction you want it for. Mercury is a noble metal, like silver, gold and platinum. The mercury is also gradually rotting through the aluminium. And, if the salt somehow finds it's way onto your skin or into your body, rotting through your neurons; as it is a powerful inhibitor of axonal growth cones. For your application, I don't think washing it or messing with mercury is the way to go. Ideally, you want the pure surface generated inside the controlled atmosphere, where it will remain pure. One method would be to apply the bias. I can't really comment on the argon ions as I have no idea how they're affect the sputtering performance, or if they'd even be a problem. You don't need to backsputter aluminium to remove the oxide. If you think of GTAW welding (TIG), the oxide layer is removed simply by switching the polarity of the power supply (the direction of the electrons); which is done automatically by the power supply. TIG welders don't like running the torch in the 'cleaning' mode constantly because it makes the electrode / torch get really hot, rather than the work piece. Another options is to let the oxide form, but blow a reducing gas in to clean it's surface. Possible candidates include hydrogen and carbon monoxide. Both fire hazards and the monoxide is also neuro and metabolically toxic. Situating the aluminium in specific positions may also be of benefit. Argon is heavier than air. If it is low down in the chamber, it will tend to remain covered in a blanket of argon until disturbed. Also consider using higher purity shielding gas. If the chamber has been vacuumed out and backfilled three times with pure argon, and then pulled down to UHV, there should be very little left in there to react with the surface.
  6. Making chlorine via electrolysis needs a selectively permeable membrane. If you check out the wiki page on chlorine there's some more information on there. One of the materials is asbestos (so a no go) and the other you may also find difficult to obtain. Electrolysis of hydrochloric acid may be the only easy electro method. Storing chlorine is also not really a good idea unless you can seal it in an ampoule, as it will of coarse be a gas at room temperature, and a corrosive one which will try to get back out of the tube over time. To store gases like that, they really need to be dry, if only so the sample looks nice. In laboratories, they tend to buy cylinders of gases like this, with the gas having been dried before being pushed in. They will usually rot the regulators, valves and even the cylinder it's self over time, so they use special metal alloys that are Nickel based instead of Iron - called Hastealloy and Monel. Both of these are extremely expensive and usually only available from laboratory suppliers. To be extra sure, the regulators are attached to a manifold that goes between them and the cylinder. After use, the cylinder is closed and dry, inert gas is blown through the manifold and regulator, to blow out any moisture and the remaining corrosive gas. Such a manifold & regulator will set you back over $1k. Dripping concentrated hydrochloric on manganese dioxide (which is one of the main components of most none rechargeable batteries) is one way to make it. However, you may have seen the Nurd Rage video about manganese dioxide, in which he receives a bag of it apparently cut with sand. Similarly, I have bought "99%" pure powder before and discovered a significant amount of it unreacted at the bottom of a flask. Meaning mine is also likely cut with something (like activated carbon). This is only really important if you need a precise amount from the gas generator. You can also make it, probably more reliably, by dripping HCl(aq) onto TCCA, which is used in some pool tablets. As someone pointed out earlier, the serious danger with chlorine is not really how you feel on inhaling it, but how you feel three hours later. Provided you make very small amounts, it's not going to hurt you. The trick being, start with a tiny, tiny quantity. Using just a few drips of acid onto less than a teaspoon of your powder. And get used to it from there. Concentrated chlorine can overpower your ability to determine whether or not it's still at a dangerous concentration immediately afterwards. Inhaling a concentrated amount of it feels like inhaling bleach. It burns and causes voluntary coughing. Around two or three hours later, if you have inhaled any significant amount, it will feels as though your being suffocated (as you are being suffocated); you'll continue coughing and producing phlegm. Feeling out of breath / dizzy / chest feels like it's been hit. With severe exposure, you will die in this period of time. So you really need to be able to judge whether or not it's time to make a hospital visit. I have experienced this myself, and it's not pleasant at all. It is worse than SO2 or HCl(g) in my opinion. Numerous people have died as a result of mixing incompatible cleaning products; in one report I read, they had to start locking the cleaning equipment away in a hospital because more than one person managed it in the same building. With that said, here are some photos of glassware setup to generate chlorine, along with it's (not particularly intense) lime / yellow colour. The first imagine is before I set the generator off; This a flask of water it has been bubbling through for about 6-9h For fun... here's some Iodine as well. A far easier halogen to collect and use given that it is solid at room temperature. This flask is hot, so some of it is floating around as a faint purple tinge And there's some in ethanol. That's 25g in 45ml, with a fair amount still sat at the bottom as a solid. The solution is currently boiling, without any heat applied, as the iodine is quite violently reacting with some aluminium powder that is also in there. The colour of iodine changes depending on it's concentration, from faint yellow / amber / orange, to purple, to what looks like black (but is in fact extremely dark purple).
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