Thanks for the responses, guys. Very helpful.
Richard: I don't think I've ever envied you your wintertime
temperatures, but I can see the utility of an infinite supply of very
cold air for this operation :-)
(I am now eyeing my 12 qt stock pot which, with only minor rearrangement
of shelving, will fit in the freezer.)
--Steve
On 2/14/24 7:42 AM, Richard Nakka wrote:
Steve...your suggestion of using an aluminum container for cooling is a good one. From my experience, that speeds up cooling. I do my recrystallization in winter. As such, the container is placed outdoors in a location where there is a strong breeze. The convective effect greatly speeds up cooling. Is it feasible to place a battery powered fan in your freezer to achieve this effect?
We make sure and regularly stir the crystals as cooling takes place. Else you end up with a large single mass of crystals that is hard to deal with when washing. This may not be such a factor with a small (1kg) batch, however, we recently recrystallized 20kg of 'dirty' KN, split into two batches. A large lump of crystals of that size is a problem.
Richard
On Wed, Feb 14, 2024 at 8:08 AM Steve Peterson <dmarc-noreply@xxxxxxxxxxxxx <mailto:dmarc-noreply@xxxxxxxxxxxxx>> wrote:
I'm about to try synthesizing KNO3 according to method 4a here:
http://www.nakka-rocketry.net/knsyn2.html
I notice that two of the steps (4 in total since each is performed
twice) seem to be particularly time consuming (in clock time, not
labor
time), namely, the chilling to -10C (and -5C) and the drying steps. I
don't mind spending all day doing this, but I'd like to get more than
700g out of the ordeal, so I've been wondering if there aren't
some ways
to improve throughput.
One would be to increase the batch size, but that seems problematic.
Another is to do multiple batches in parallel, which would be easy
for
the drying steps (just use more cookie sheets and counter-space),
but is
harder for the chilling steps since freezer space is limited.
A third method would be to chill faster. The directions mention
using a
poly container for this step, but I'd think an aluminum one would
help
to speed up the process (slightly). But I was thinking a cooler
containing dry ice might get the chilling time down to ten minutes
or so
(just speculating--haven't done any calcs/measurements).
But then I wondered if maybe the long chilling time was a feature
not a
bug in that maybe the crystals just take a certain amount of time to
form and perhaps speeding up the process would hinder their growth
and
thereby limit the yield. Any experience/thoughts on this?
Likewise, I was wondering if the mixture should be stirred during
the
chilling process (to even out the temperature of the liquid) or
left still.
Thanks for any help,
--Steve
