[AR] peroxide freezing (was Re: [UK OFFICIAL] Moon Express - HTP/kero)
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Mon, 17 Jul 2017 14:56:21 -0400 (EDT)
On Mon, 17 Jul 2017, Ben Brockert wrote:
Peroxide solutions undergo fractional crystallization as they are frozen, so
whether the bulk material expands or contracts is basically a question of
which ice is winning. 65% being the balancing point suggests that peroxide
contracts about half as much as water expands.
It's not a sharp tipping point, though -- expansion occurs below 45%,
contraction above 65%, and in between it's complicated. The guys who
measured this complained: "the behavior of the system during
crystallization is often erratic".
(Gigue`re & Geoffrion, "Changes of density of hydrogen peroxide solutions
on cooling and freezing", Can. J. Res., 1950, 28b(10): 599-607.)
The same paper notes another complication of trying to thaw out a frozen
peroxide system: frozen peroxide often decomposes significantly during
thawing! They say that the small needle-like crystals formed in certain
conditions have streams of decomposition bubbles coming off their tips as
they melt. It's not a matter of impurities -- it happens only while the
crystals are melting, and stops instantly when they disappear, or when the
temperature is lowered again and melting stops. Another good reason to
make sure that your peroxide supply doesn't freeze...
Henry
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