John Cuthber

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John Cuthber last won the day on May 2

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About John Cuthber

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    Chemistry Expert
  • Birthday 11/10/1965

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  1. John Cuthber


    Like circularly polarised light?
  2. John Cuthber

    Frequency multipliers

    I wonder if anyone has ever set up a chain of frequency multipliers (doublers or whatever) to convert the very accurate 60 KHz signal used by radio controlled clocks up to something in the MHz region for calibration/ checking of frequency meters. You can get multipliers designed for this but they are PLL based. A sequence of accurate 60, 120, 180... KHz test frequencies might be useful. A trippler gives you 180 KHz and a quintupler gives you 300 KHz Any thoughts?
  3. John Cuthber

    Activated carbon home air purifiers and dioxins

    Yes. Because dioxin, with a vapour pressure near 10-^-9 mmHg is practically involatile so it isn't a vapour hazard. Any dioxin "in the air" is almost certain to be stuck to dust. Any filter that strips the dust will also remove practically all the dioxins. Why bother with activated charcoal? Yes. In the case of ozone , it reacts to give carbon monoxide . Charcoal will remove the other compounds- until the filter is saturated. It is difficult to be sure if the filter is saturated. Some materials are more strongly retained than others and you can have a situation where one material displaces another.
  4. John Cuthber

    Some Thoughts on Air Conditioning

    I'm fairly sure that what you propose is a breach of the laws of thermodynamics.
  5. John Cuthber

    CH3OH + 2CuO Which reaction is true?

    Hot copper oxide is used in classical chemical analysis to convert organic compounds to carbon dioxide and water. What mixture of products you get will depend on temperature, contact time, proportions and other stuff. Passing methanol vapour over hot copper (metal- not oxide) will produce formaldehyde. The commercial synthesis uses silver, rather than copper.
  6. John Cuthber

    How to remove iron from mercury?

    Iron does not dissolve in mercury.
  7. John Cuthber

    What is 4 divided by 6?

    No. Six divided by four is 1.5
  8. John Cuthber

    yield and ultimate fail in battle

    To a good approximation; nothing ever fails in straight compression. You may find this next equation helpful. The (average) force exerted by an object when it comes to a halt is equal to the (average) force used to accelerate it times the ratio of the distance it was accelerated to the distance over which it stops. So, if I drop a rock that weighs 1 newton off a table that's a metre high and it comes to a halt when it hits the carpet which is 1 cm thick, the average force on the floor is 100N. It's also important to recognise that the "strength" (however you measure it) of the object which strikes a target isn't as important as people think. You can cut steel with water if the water is moving fast enough.
  9. John Cuthber

    10 to 1

    Would you like to try that again, but with more rational explanation and less dross?
  10. John Cuthber

    10 to 1

    Well, that's a matter of theology. The fact that the acceleration due to gravity at the Earth's surface (9.80665 m/s/s) is near, but not exactly, 10 m/s/s is down to whoever designed the Earth.
  11. John Cuthber

    A liquid which absorbs EMF?

    Not strictly a liquid but you can pour it... metal shot would also act as screening. I can't think of a solution involving any liquid that doesn't include sealing the phone in a bag or something (unless you don't care about ruining it). If you are going to seal the phone in a bag anyway, you might as well wrap it in foil.
  12. John Cuthber

    A liquid which absorbs EMF?

    I suspect it is very toxic to mobile phones. Mercury vapour will damage aluminium and solder.
  13. John Cuthber

    How to determine if Aluminum or Zinc?

    Well, it's 6 HCl + 2Al --> 3 H2 + " 2 AlCl3 But that's hardly important. Both metals (indeed most metals) react with dilute acid to give hydrogen gas. However, if you take the solution of metal chloride and add an excess of ammonia solution you get different results. With zinc you get a precipitate of Zn(OH)2 but that dissolves when you add more ammonia. With Al you get a white precipitate of Al(OH)3 which doesn't dissolve when you add more ammonia. It's worth doing the reactions on known materials first so you get the "feel" of it. Having said that, Aluminium is about a third of the density of zinc, and that's often a pretty good way to tell them apart. Also, it is very common to find alloys that are a mixture of aluminium and zinc.
  14. John Cuthber

    Fire in Notre Dame in Paris

    And my garden bonfire- which didn't. The common factor is fire, not lead. Some lead will have been boiled off into the air. And, by now it will have been washed out by the rain into the rivers.
  15. John Cuthber

    Fire in Notre Dame in Paris

    I think the traditional response is " No shit, Sherlock". Would you like to compile a list of dusty old churches where that was not the case?