[NewCandle] crystallization weight change transients

[Nick Reiter]

Update for the week's end...

I tried working with NaOH on Thursday.  It has a
gradient of solubility with temperature, but will not
remain a stable supersaturated solution down at room
temperature without spontaneously self-seeding and
recrystallizing.  I could not get it to work.  It was
similar to CuCl2 and NiCl2.

Whilst in the grocery store at lunch time yesterday, I
spied a container of epsom salt - MgSO4 heptahydrate. 
Why not, I thought.

Ran a couple of tests with it yesterday and this
morning.  Not a real easy player.  Slightly exothermic
when it crystallizes, but does so verrryyy slowly, and
like the NaOH, is prone to self seeding below about
27C.  I may have gotten a wee hint (submilligram) of
loss with epsom, but it was complicated by me having
to start at a slightly higher temperature, thus having
some amount of flask cooling as the crystal growth was
warming up.

I have not tried sucrose yet, and I don't have enough
citric acid left from the anode glow experiments a few
months back.

So far, sodium hyposulphite - while more exothermic
than the hypo-P - seems to give the best bang for the
buck.  Wise choice on the old boys' part.  Unless I or
someone can find a rapid crystallizer that is
endothermic or near neutral, I guess the next step is
to design a test vessel that the run can be made in,
that will disentangle heat transfer from any potential
"anomaly."

I'll work on this next week.  I'm thinking of a
homemade double wall test tube vacuum bottle small
enough to fit on the balance pan.  A baseline run
could be made with a resistor as a variable heat
source inside it for starters.

And thats where I'm at...

N

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