Jump to content

John Cuthber

Resident Experts
  • Posts

    18280
  • Joined

  • Last visited

  • Days Won

    46

Everything posted by John Cuthber

  1. Well, you can use a concave mirror to focus the beam of a transmitter too.
  2. Depends what you mean by elliptical. The curve on a concave mirror is often part of a sphere because they are easy to make but parabolic and ellipsoidal mirrors are also made. The mirror that focusses the light from a flash tube onto the ruby rod in a "classic" ruby laser is elliptical. It would work perfectly well for radio waves or microwaves.
  3. Why would there be one? (and I'm an analytical chemist BTW)
  4. There are lots of different fungi called penicillium. Very few produce penicilin. http://en.wikipedia.org/wiki/Penicillium
  5. Long ago when I was at school I noticed that there were transformers in the boxes with the speakers in. I later learned that these meant that the signal could be distributed at a higher voltage (typically about 100V) and lower current. Since the current is quite low the power loss due to the resistance of the cables isn't a problem. Searching for "100 volt line transformer" will get lots of examples.
  6. There's an article about the idea in wiki. http://en.wikipedia.org/wiki/AVLIS Perhaps the most telling quote is "In the largest technology transfer in U.S. government history, in 1994 the AVLIS process was transferred to the United States Enrichment Corporation for commercialization. However, on June 9, 1999 after a $100 million investment, USEC cancelled its AVLIS program." People don't generally cancel things that look like they might work in practice. Anyway the answer to the question is more or less "the 238U absorption peak shifts from 502.74 nanometers to 502.73 nm in 235U." because you can then use a second laser (that is only absorbed by the excited species) to do the ionisation. That's a perfectly big difference if you are looking at a laboratory process, but it's a rather small one if you are looking at commercial production.
  7. I think I read it somewhere on the net as an example of how the "land of the free" is a bit of an irony. You can buy a gun but not a three necked flask.
  8. Liquid nitrogen is stored in Dewar vesels with loose fitting lids for several days or even weeks in the lab where I work. We don't keep it under pressure. Large storage Dewars are pressurised, but this is for ease of dispensing rather than to stop it boiling. http://www.cryospeed.co.uk/cryospeed/equipment/dewars_and_accessories/25_litre_dewars_and_accessories/index.asp Anyway, as has been pointed out, dry ice simply isn't cold enough to freeze all the components in crude oil. Also the mixture will have a lower freezing point than the components so I think the best you would get would be a very viscous goo. With liquid nitrogen you could freeze it, but it would melt as it warmed up so a block of it wouldn't lst long. What on earth do you want it for anyway?
  9. They are sometimes known as "hot wire" meters. http://www.practicalphysics.org/go/Experiment_698.html;jsessionid=alZLdQlAHb1
  10. Sometimes I'm amazed by what you can find on the net. http://www.elephantdungpaper.com/
  11. Bones are largely calcium phosphate, but they are toughened by the presence of proteins. I doubt that those proteins are exaclty the same in fish as they are in lamb or beef. Careful extraction of the protein followed by analysis would, I'm sure tell fish from meat, and I think it might tell you a bit about the species of fish too.
  12. If it fizzes in boiling water it's still sodium bicarbonate and I'm pretty sure that it would be stable for years under normal storage conditions. I will look at the expiration date on the stuff in the lab if we have any.
  13. The Americium in smoke detectors is a fissile material and I'm pretty sure it's legal to own one. I wonder if the lawyers have written some law that forbids making an atom bomb.
  14. Perhaps I'm just naturally suspicious. Is this a question about "If I put a magnet next to the meter that the electricity company installed will it go round more slowly and give rise to a smaller utility bill?"
  15. The good old US of A - the land of the free. (I think I'm allowed to do it here in the UK but I'm not sure). IIRC the OP is based in a state where owning lab glassware is restricted anyway, so the local laws on radioactive materials are likely to be strict.
  16. I'm not a lawyer but I think that the answer to the OP's question is yes, but not legally. The Am in those detectors is only exempted from the license system because it is part of an "exempted product" . If you take it out of the smoke detector you are breaking the law. Also, it's not nice stuff to play with.
  17. What soluble form could a base bath convert the iron into? It's quite possible that the heat of the Fe +S reaction will have partly melted the glass in which case cleaning it won't help. On the other hand, if it's just got FeS stuck to it, then you need something that will dissolve FeS. What is the classic way of making H2S in a lab?
  18. Is this just for interest or is there some reason you can't just use wax?
  19. OK so you took the trouble to make Na from NaOH and you are thinking about making Cl2 from HCl. Then you ask what other way there might be of making salt? Did you really not think about just dissolving the NaOH in water and neutralising it with the HCl? I know this site is full of people doing things the hard way, but they usually know that that is what they are doing.
  20. This stuff was meant to be the oxidised form. It hasn't oxidised. Adding steel wool would turn it into something else. It has, as was pointed out earlier, picked up watter (possibly lost HCl too) and hydrolysed. In solution FeCl3 is greenish yellow (usually with a brown sludge at the bottom) This is the colour of the FeCl4- ion.
  21. It's a matter of deffinition I think. The "poisons" are nuclei with high netron capture cross sections. They do that whether they are dissolved inlight or heavy water or, for that matter , if they are in the gas phase or anything else. On the other hand, because the capture cross section for heavy water is less than that for light water, you can get away with a slightly higher concentration of "poisons" in heavy water.
  22. Carbon disulphide is nearly spontaneously inflammabe, it's neurotoxic and it smells like a rank fart. Surely there's some other solvent you could use?
  23. 2 days later and no comment from the OP. OK so I'm paranoid, but; the evidence that this is not a "drive-by trolling" is what?
  24. What did you make the sodium from?
  25. Claim that science is your faith and that they are depriving you of the right to worship here.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.