[time-nuts] CS reservoir depletion

J. Forster jfor at quik.com
Sat Jan 15 04:13:54 UTC 2011

> I used to perform Rb/Sr geochronology "wet bench" chemistry in
> college.  Rb-87 has a half-life on the order of ~48.8 billion years.
> Several multiples of the estimated age of the universe.  The
> potassium-40 in your own body is a much greater threat, followed by
> C-14, and various natural sources, smoke detectors, camping lantern
> mantles, etc... I understand the average person has several thousand
> K40 decay events in their body per second.

I don't know the number od K-40 decays per second, but it's certainly
non-trivial. Asw a freshman science project, I went into a chamber made
out of pre-atomic age battleship armor plate and had the K eminations
counted with a scintillator and MCA. From that measurement, we were able
to determine my "lean body mass".

> Handling pure Rb is another thing entirely.  It is quite moisture
> sensitive / pyrophoric, and tends to form shock sensitive peroxides
> even when submerged under oil.  You really need to store the stuff in
> a vacuum, or under an inert atmosphere.  But since we're also
> discussing Cesium, I should point out that it is actually far worse
> in this regard.  You could probably safely handle a small quantity of
> Rb in a home lab environment for a short period of time.  Pure Cesium
> would be a significant risk.
> Rob

I think any pure alkali metal basically has to be handled in a good vacuum
and moved around by distillation. It's easy enough as you are concerned
with grams, at most, not pounds of the stuff.



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