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    Re: Children's land-locked "Sextant"
    From: Alexandre Eremenko
    Date: 2007 Nov 28, 23:17 -0500

    
    Mercury is not very dangerous
    (if you don't drink it).
    However it is extremelly harmful for the environment.
    Even a small amount can poison all fish in a lake.
    That's the main reason why its use is severely restricted.
    For example, beginning January 2007 you cannot buy
    a mercury barometer on e-bay. The last internet store
    in the US that was selling them does not do it anymore
    since the beginning of 2007.
    Some states in the US prohibit selling buying and
    manufacturing of mercury barometers and termometers.
    
    Alex
    
    On Wed, 28 Nov 2007, Geoffrey Kolbe wrote:
    
    >
    >
    > Gary LaPook wrote:-
    >
    >
    > >With use it develops a dross floating on the surface which can be
    > >removed by filtering it through a piece of cloth like an old t-shirt.
    > >You have to twist the cloth to force the mercury though the cloth and
    > >it comes though in shiny little balls leaving the dross in the cloth
    > >which I then dispose of. You should probibly wear gloves when handling
    > >the mercury like this.
    >
    > In the 1960's the old Royal College of Science in London was pulled down to
    > build Imperial College, the British attempt to emulate MIT in the United
    > States.
    >
    > The Spectroscopy labs in the RCS had long been plagued with the problem
    > that continuum spectra always had absorption lines of mercury on them. On
    > taking up the parquet floor in the lab, a veritable lake of mercury was
    > found underneath! As far as I know, all the researchers of that era lived
    > to a ripe old age, despite working for many years in an environment where
    > the mercury vapour in the air was probably at saturation point.
    >
    > Not that I am advocating that we should not take suitable precautions when
    > using poisonous substances like mercury - its just that people somehow seem
    > to be more susceptible to such things than they used to be in times
    > past.... or, at least, that is the perception.
    >
    > Geoffrey Kolbe
    >
    >
    > >
    
    
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