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John Cuthber

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Posts posted by John Cuthber

  1. On 10/7/2021 at 11:46 AM, Brian King of Trolls said:

    First, it expresses itself as the evolution of space and cosmic matter: stars, galaxies, planets. Next, through biology: the self-evolution of a physical body, and a higher dimension of experience. 

    Actually, those processes are (by the laws of thermodynamics) driven by a net reduction in organisation in the universe.

    It's true that trees grow, but it's also true (and a necessary part of evolution) that trees die.

    The expectation is that the universe will end up cold dull and empty.

     

    Your problem is only looking at yourself and the things near, and like, you.
    We may be getting more complex; so is life.

    But the universe isn't.

  2. Long ago, at school I really pissed off the metalwork teacher.

    He had just finished explaining to the class about pickling copper after annealing it. You wash it in 10% sulphuric acid to remove the oxide film.
    They also pointed out that you had to use the special brass tongs because the acid would damage the (usual) steel ones.

    And, of course, he made a big song and dance about being careful with the acid.

    It undermined his authority when i just took stuff out of the bath with my hands and rinsed it under the tap.

    Dilute sulphuric acid does attack normal human skin, but slowly.

    Washing your hands in it is stupid bravado (and yes, that applies to me doing it when I was a school kid) but it doesn't imply any superhero skills.

    I doubt I ever got through a gallon of coffee in a day, but when I was a student I was getting through half a dozen caffeine tablets with my breakfast.

    Lethal doses of caffeine  taken rapidly- are of the order of 5 grams.

    A cup of coffee is of the order of 0.1 grams.

    So, 50 cups of coffee at once would kill you .

    But a gallon over the course of a day is just an expensive (and unhealthy) choice of drinks.

    One obvious effect would be an extra gallon of piss every day.

    That's rather a lot.

    Enough, for example, to wash out a lot of any medical drugs you took before they had time to work.

    So the idea that it takes 4 times as much medicine to have an effect isn't a miracle either.

    There's nothing here to investigate.


     

     

  3. 2 hours ago, Externet said:

     Trying to make a coupling disc from CGA870 to CGA850 valves to fill high pressure cylinders. 

    I once got asked to analyse the stuff found on the inside of a burst gas cylinder.
    They were trying to work out what had happened.
    There had been a witness- very very briefly- but he wasn't telling us anything anymore.
     

    (re)filling high pressure cylinders isn't as easy as people thing.

    It's also often illegal.

    This is not the sort of thing to do with "string and sealing wax" as the phrase goes

    https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10309/1030908/Whatever-happened-to-the-string-and-sealing-wax/10.1117/12.2283713.short?SSO=1

  4. On 9/24/2021 at 1:35 PM, studiot said:

    I look forward to your scientific amplification of this claim.

    Which bit don't you understand?

    This
    https://en.wikipedia.org/wiki/Nernst_equation
    which says the voltage depends on the pressure, 

    or do you not understand the idea that you can store gas at constant pressure in something like this?
    https://en.wikipedia.org/wiki/Gas_holder

     

    Since the gas pressure never changes, the gas is never compressed, no work is done compressing it.

    On 9/24/2021 at 2:13 PM, swansont said:

    You might not need to do work to compress it, but that would mean you expend more energy generating it. That bill still needs to be paid.

    That's why the voltage is higher.

  5. 1 hour ago, studiot said:

    Actually no I didn't introduce liquid hydrogen into the thread, the OP did.

    He pointed out that it's impractical.
    "Liquid hydrogen must be contained at incredibly high pressure or maintained at very low temperatures by complex cryogenic systems. "

    As far as I can tell, only space rockets use LH2 as a transport fuel- and even they sometimes shy away from it.

    I don't know of any serious project that is looking at LH2 as an energy storage medium .
    There are two reasons.
    1
    it's hard.


    2
    It's inefficient- you waste a lot of energy cooling and heating it.

     

    The thread is about an new trick in the process of making hydrogen; what you do with it after that is a separate issue.

     

    Incidentally, 
     

    2 hours ago, studiot said:

    How much energy in the form of work needs to be input to collect and store hydrogen gas or liquid in reasonable sized containers ?

    If you generate the gas electrolytically, the answer is "none".

    You don't need to do work compressing it; the reaction will still work at higher pressure but needs a slightly higher voltage.

    Hydrogen generators exist, so they are clearly "reasonable"

  6. Just now, studiot said:

    o what state might I expect a hydrogen tank and connection pipework to be in after 25 years bouncing about in a vehicle ?

    Well... pretty much the same as a petrol tank.
    And there are plenty of 25 year old petrol fuelled vehicles on the road. They aren't all suddenly exploding, are they?

    At most, you need to add another line to the MOT test "leak test the tank".


     

     

    2 minutes ago, studiot said:

    And whilst we are discussing it, hydrogen boils at -253oC whilst LPG boils at -42oC   A world of difference in technological terms.

    And LNG boils at about -162, and nobody is considering it as a transport fuel either.
    Why did you raise the issue?

    On 9/21/2021 at 11:46 AM, studiot said:

    Indeed so but you have not addressed my basic point that people are people and do not act in a technologically optimum way.

    They never did.

    That's why we have regulations.

  7. 19 hours ago, studiot said:

    Those were not incidents involving hydrogen.

    Hydrogen has one property which makes it rather more hazardous than natural gas- it has a very low ignition energy.
    On the other hand, the low molecular mass and comparatively low energy density (a litre of hydrogen carries less energy than a litre of methane) tend to reduce the risk. to exactly the same extent that it will leak through a badly made connection, it will also leak out of the area it is released into.

    There's a story of a demo where they emptied a tanker truck of liquid hydrogen onto the surface of a lake, waited 5 minutes and struck a match.

    They then invited anyone to do the same with petrol/ gasoline.

    Any fuel is, ipso facto, potentially dangerous.
    The way round that it to not let it escape.

    5 minutes ago, studiot said:

    It is a very small molecule and therefore difficult to contain, most especially in old perhaps poorly maintained equipment. Leaks are more likely than with say propane.

    Not really.

    Once you tighten up the fittings so that the metal meets the metal, there's no hole.

    Practically speaking, Hydrogen won't diffuse through a mild steel pipe any more than propane will

  8. 2 hours ago, exchemist said:

    Right. But in gas discharge tubes? I doubt that CuCl2 is used,

    They typically use CuCl.

     

    2 hours ago, exchemist said:

    What I am having difficulty tracking down is what fluorescent material is used to produce green. My first guess would be an organic dye. Any idea?  

    Almost certainly not an organic dye. The tubes are typically coated on the inside- much like an ordinary fluorescent tube.

    That's a rather aggressive environment.
    These are more likely.

    https://en.wikipedia.org/wiki/Phosphor#Standard_phosphor_types

    though just painting a clear lacquer onto a white tube would work, as long as it was heat resistant enough.

  9. The emission spectra are changed slightly by a magnetic field.

    https://en.wikipedia.org/wiki/Zeeman_effect
    But the effect will be too small to see unless you have a tremendously strong magnetic field.

     

     

    On 9/18/2021 at 8:19 AM, exchemist said:

    I am also unaware that CuCl2 is used to modify the colour. Can you provide a reference for this? 

    The commonest use of copper chloride in this way is in fireworks.
    The colors of most modern fireworks involve a few metal chlorides, which fluoresce strongly in the visible wavelengths: Barium chloride produces green; strontium chloride produces red; and copper chloride produces blue.
    https://cen.acs.org/articles/95/i27/s-fireworks-produces-those-colorful.html

    But it's also used in lasers

    https://www.repairfaq.org/sam/laserccb.htm

     

  10. 13 minutes ago, Hans de Vries said:

    Do you think domesticated Caribou could be selectively bred to a size similar to that of horses and provide a viable alternative to horses in North America?

    Raindeer were domesticated and raindeer and caribou are practically the same. 

    They are the same as reindeer (note the spelling, btw).
    Caribou have been semi domesticated for a long time.

    Not sure there's much advantage over a horse.

     

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