[time-nuts] time-nuts Digest, Vol 108, Issue 55

Jim Lux jimlux at earthlink.net
Wed Jul 10 23:29:01 EDT 2013


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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