[NewCandle] crystallization weight change transients

[Nick Reiter]

Update for the past 2 days...

Short version... I believe there is a good chance
something real is going on.  But the thermal artifacts
are not as straightforward as I would have hoped.  I
guess they never are.

Yesterday, I stuck with the hyposulphite.  I added
about 20 more grams of the material to the solution,
and it still seems stable before triggering.  Now,
when she launches, she really launches into a
crystallizing mode, and when done I have about 80%
volume of the flask filled with crystals.  I can then
put it back on the hotplate, re-dissolve at about 80C,
and then it's stable again until seeding.  Of course
each time I trigger, it adds another seed-worth of
salt to the solution, but it should give me quite a
few runs.

Anyway, with the maxxed out volume, I got about 4+
milligrams of loss in about 13 minutes total time
(most within 4 minutes) with a temperature rise of
about 11 C degrees.

So last night, I prepped the flask with the cool
re-dissolved salt, and I coated it (the flask) with a
layer of spray on filler foam to make a conformal
puffy insulation layer around the entire flask.  I let
it dry til this morning.  As I was getting ready to
place the flask on the balance to proceed, I knocked a
tiny flake off the rim into the solution and whooosh,
she took off.  I got it on the balance quickly enough
to save the experiment.  Wow - within about 8 minutes
I had a 17 milligram loss with only a couple degrees
rise on the outside of the foam.  Then I slapped
myself.  I had made a bunch of tiny hot air balloons
in the bubbles in the foam, right around the flask
surface!  Agh.  Dumkopf.  I watched it off and on for
an hour or so, and the weight was not returning even
then.  So I stripped off the foam and found the flask
to still be plenty warm.  Good insulation, but closed
porosity is NO GOOD - it traps warmed air.  Balloon
time.

So then I re-dissolved, and this time tried a loose
shroud of refractory fiber blanket (kao-wool).  Ran
again - this time got about 4+ milligram loss over
about the same time as the nude flask - however the
slope of the change was shallower.  Was I just slowing
down the diffusion of warmed air around the flask?

Re-dissolved once more, and tried some trials without
crystallizing - just the solution in the flask, warmed
and then allowed to cool on the balance pan, and then
re-warmed and quickly re-weighed.  Looking for T and
delta T versus deviation in weight.

So far it looks like the delta in weight versus degree
C is less than half of what I was getting with the
crystallizing runs.  But it is a factor, no doubt. 
And its not the same depending on whether one is on
the "cool down" or "warm up".  Thats probably the
biggest clue to me right now that there is a
legitimate(ly) odd component to the total event.  With
a 12 degree C difference in T, I was only getting
about a mg in weight change (on the way up).

I think I will now go back to the hypophosphite, which
looks much less exothermic.

Things that make me go hmmmmm some more.

NR

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