Although not specifically in IPA, looking at homologues we know freebase DMT is highly soluble in ethanol and only precipitates from 50% aqueous ethanol at about -18°C, rapidly redissolving with even slight warming. I can only imagine that the solubility in IPA is even higher although whether this extrapolates to IPA/water mixtures would, as endl suggests, be fairly easy to determine experimentally. I will try this out eventually.
Given that you used 99.9% IPA, it seems exceedingly unlikely that DMT would precipitate at normal domestic freezer temperatures.
The powder that has precipitated is almost certainly calcium hydroxide or calcium carbonate.
Ora, lege, lege, lege, relege et labora“There is a way of manipulating matter and energy so as to produce what modern scientists call 'a field of force'. The field acts on the observer and puts him in a privileged position vis-à-vis the universe. From this position he has access to the realities which are ordinarily hidden from us by time and space, matter and energy. This is what we call the Great Work."
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