1. Forum
  2. Usenet
  3. SCI.CHEM

  • =?UTF-8?B?QXZhZ2Fkcm8gTnVtYmVy?=

    From =?UTF-8?B?Y2FzYWdpYW5ub25pQG9wdG9ub@21:1/5 to All on Sat Dec 19 18:52:11 2020
    Ever so slightly different values are quoted in various references. The value I use is one seen frequently, 6.02214076 E23 . Other perceptions ?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Martin Brown@21:1/5 to casagiannoni@optonline.net on Sun Dec 20 13:29:06 2020
    On 19/12/2020 18:52, casagiannoni@optonline.net wrote:
    Ever so slightly different values are quoted in various references.
    The value I use is one seen frequently, 6.02214076 E23 . Other
    perceptions ?

    Unless you are doing something very unusual it makes little difference
    beyond 4 sig fig.

    Physicists care about it when calibrating the C12 mass scale and ion
    counting in mass spectrometry. Chemists tend to just use their results.

    --
    Regards,
    Martin Brown

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From mroussel@shaw.ca@21:1/5 to casagi...@optonline.net on Sun Dec 20 10:45:58 2020
    On Saturday, December 19, 2020 at 11:52:15 AM UTC-7, casagi...@optonline.net wrote:
    Ever so slightly different values are quoted in various references. The value I use is one seen frequently, 6.02214076 E23 . Other perceptions ?

    In the new (2018) SI system, the value of Avogadro's number is fixed (the same way the speed of slight was fixed a few decades ago to define the metre). The value you should use now (and forever) is 6.022 140 76 x 10^{23}, i.e. the one you quoted above.
    Any other values you might see are historical artifacts now.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From RichD@21:1/5 to Martin Brown on Mon Jan 11 11:49:33 2021
    On December 20, 2020, Martin Brown wrote:
    Ever so slightly different values are quoted in various references.
    The value I use is one seen frequently, 6.02214076 E23 . Other
    perceptions ?

    Unless you are doing something very unusual it makes little difference beyond 4 sig fig.
    Physicists care about it when ... ion counting in mass spectrometry

    What exactly is ion counting, and how?

    —
    Rich

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Martin Brown@21:1/5 to RichD on Tue Jan 12 11:31:59 2021
    On 11/01/2021 19:49, RichD wrote:
    On December 20, 2020, Martin Brown wrote:
    Ever so slightly different values are quoted in various references.
    The value I use is one seen frequently, 6.02214076 E23 . Other
    perceptions ?

    Unless you are doing something very unusual it makes little difference
    beyond 4 sig fig.
    Physicists care about it when ... ion counting in mass spectrometry

    What exactly is ion counting, and how?

    Imagine a photomultiplier tube but without the glass envelope and
    already in a vacuum chamber. Hit it with an ion at 8kV acceleration and
    it spalls a cascade of electrons. You don't need so many gain stages.

    There is a limit to how quickly it can recover (dead time) - ours used
    to max out at about 10MHz. They can also be run at a much lower gain in
    a pseudo analogue sort of way as a current detector.

    This lot claim to be up to 1GHz ion count rates now. No idea if it is
    genuine and works as advertised. I don't work on that stuff any more.

    http://www.cromlab.es/Articulos/SGE/ETP/TA/TA-0103-A.pdf

    --
    Regards,
    Martin Brown

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)