On 7/10/13 2:15 PM, Max Robinson wrote:
I think that luminous dial watches still contain a little tritium to
keep them glowing for many hours after the atoms that were excited by
visible photons have all decayed. Without the tritium the glow would
completely go dark after most of the atoms have decayed to their ground
state.
luminous dials use some form of activated zinc sulfide. No radioactivity
involved.
Tritium is actually quite dangerous just because of the tritiated water
problem. Beta emitters, sitting in a lump on the table, aren't as
hazardous, because it's easily shielded. Your skin absorbs most of the
beta particles (aka electrons), so you would get burned, perhaps.
However, if you ingest a beta emitter, now you've got a beta emitter
close to sensitive cells. Tritiated water is easily ingested, absorbed,
and otherwise winding up close to sensitive tissues.
It's like why plutonium or radon, alpha emitters, are such a problem.
If they become airborne and ingested into your lungs, you've got a alpha
emitter close to lung tissue which is peculiarly sensitive. In fact, I
seem to recall that a significant reason why cigarette smoke is
carcinogenic is that it has tiny particles which carry radon and other
similar nuclides deep into the lungs.
Getting back to Rb safety...
It's pretty reactive, and all the salts are unlikely to be ingested and
absorbed. Not like you're going to be sprinkling RbCl on your steak.
There's a video on the web about alkali metals reacting with water, but
it used pyrotechnics to "enhance" the Rb and Cs reactions.
From practical experience, Li is the most spectacular, Na is really
bright, K isn't as exciting as either, but is a pretty color. Li has
that brilliant scarlet color. I think the Na is bright because of the
reaction energetics, and because the sodium yellow is closer to your
eye's maximum sensitivity. If you're looking for maximum bang for the
buck, I think Sodium is your alkali metal of choice. I've always wanted
to try a Na/K eutectic, though.
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