so SWIM has access to a -70 C freezer and was wondering if freeze precip. in this very cold freezer with 150 mL of Naptha w/spice would work or would it or could it possibly be cold enough to freeze the Naptha?

SWIM also ponders how long it would take for xtals to precipitate at such a cold temp?

Naphtha would freeze (about -30°C for shellite if I remember correctly), BUT heptane would not! Pure n-heptane has a freezing point of about -90°C, so it would be perfectly fine. If I had access to such a freezer, I would definitely try splitting up a heptanepull into two containers, one which goes into my ordinary freezer (ca -20°C) and the other one into -70°C, just to compare the yields. Might be quite interesting. Please report if you try!
About the time, it of course takes as long time to fully precipitate as it takes for your heptane to reach -70°C (test with a thermometer). Then add a couple of hours for the free molecular-dust to settle and form crystals on the bottom of your container.