Re: barium titanate doorknob caps/beryllium

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Original poster: "Dr. Duncan Cadd by way of Terry Fritz <twftesla-at-uswest-dot-net>" <dunckx-at-freeuk-dot-com>

Hi Ed, Jeff, All!

Happy Easter!

>> Keep in mind though that Barium anything (salts, oxides, nitrates
etc) are
>> very toxic.
>> --jeff
>
> I think you men Beryllium rather than Barium.  As anyone who has
ever
>had a GI X-Ray exam, it is quite common to use Barium (something
>soluble, don't know which salt) taken internally to define the
>intestines.  Don't believe that would be done if it were toxic at
all.
>Ed


Well actually Jeff is right and Ed is right.  Soluble barium salts are
toxic.  The stuff used in barium meals is a suspension of finely
powdered barium sulphate (or possibly sulfate ;-) which is highly
insoluble - just a quarter of a milligram dissolves per hundred ml of
water at 25C (it occurs naturally as barytes or "heavy spar") and
therefore non-toxic because the barium is locked up by the sulphate
ion and not accessible to the body.  Barium, when accessible to the
body's chemistry, is toxic.  However . . .

Beryllium on the other hand (as found in beryllium copper alloys, high
power transistors etc as salts used for a heatsinking material within
the case) is in a different league.  It is _very_very_ toxic and is
absorbed and accumulates easily in the body, so this may be an
opportune moment to get on my chemistry soapbox and sound a general
note of warning on beryllium.

You really should avoid machining, filing, heat-treating/welding etc
beryllium alloys under home workshop conditions as the dust/vapour
will do you a lot of serious no good. The pros can summon the aid of
all manner of air monitoring, regular blood testing, containment and
filtration mechanisms outside the range of an enthusiast's workshop.
Never, never cut open a power transistor case.  Not all of them
contain beryllium salts, but the risk isn't worth it.  If you have
done any of these things, consider a blood screening seriously.

One of my ex-professional colleagues did a fair percentage of all the
world's known organometallic chemistry of beryllium.  His research was
officially stopped because of the toxicity problems - and this was in
the 1970s so you can guess how it must have been to attract attention
from officialdom back then.  (Back then, we were still boiling benzene
on the open bench.)  If you're into literature searching, look for
papers by Prof. Coates of Durham uni, which might also bear the name
Tom Caygill (my colleague, who was Prof. Coates' technician and who
actually did most of the benchwork.)

Dunckx