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Precipitation temperature

C

CokFLHX

Rising Star
Hello.

I’m gonna be pushed for time and am going to have to try to collect free only fur hours in the freezer.

On its coldest setting, the freezer chills down to degrees, per the thermometer placed inside.

I guess it doesn’t really matter. Gotta do what you have to do, but it got me curious is there was any data on freeze precipitation at different temperatures.

I understand that in that time it will not have precipitated all the material in solution. Just curious.

Thanks.
 
Slower cooling produces bigger crystals, and the lower the temperature, the more complete the precipitation. It's really far better not to have to hurry these things.

Precipitation of crystals occurs from a saturated solution when the temperature drops. Supersaturation can occur if there are no suitable nucleation points present, so you may want to consider how that may pertain to hastening the crystallisation process.

If you have warm naphtha, you would probably benefit by cooling it off using a cold water bath as temperature transfer to and from water is far more effective than with air. Be careful not to get water into the crystallisation dish!

Once the naphtha has cooled to room temperature or below you may be able to observe clouding of the solution - maybe even a few crystals if you're lucky. At this point, it may be possible to extend the cooling bath idea by using some kind of freezing-resistant liquid which you will have pre-chilled by placing it in the freezer before anything else.

Suitable liquids may include antifreeze (but be aware of its incompatibility with foodstuffs - take precautions against spillage!) or a strong calcium chloride solution. This latter one can be obtained easily from the single-use room dehumidifier packets, which liquefy into saturated calcium chloride solution after absorbing moisture from the air. You can throw the granules into some distilled water and filter off the impurities - mostly chalk and rust - and the resulting solution resists freezing down to -55°C when it is saturated, although calcium chloride will crystallise out as the temperature drops. (This crystallisation occurs in almost the exact same way as DMT crystallising out of naphtha.)

In the absence of calcium chloride, table salt will do but saturated brine will freeze at -22°C. You'll need to ensure that it's contained effectively should it happen to freeze solid.

If all this appeals to you, put the freezing bath in the freezer now, so that it's ready to receive your pre-cooled naphtha when you have that ready. You will need to ensure that your dish of naphtha can remain absolutely stable and not tip, slosh or spill in the freezer should you decide to do this.

One important footnote about heat-transfer baths is that one should, of course, always take displacement volume into account so that the coolant does not overflow when an item gets immersed in it.
 
Transform said:
Slower cooling produces bigger crystals, and the lower the temperature, the more complete the precipitation. It's really far better not to have to hurry these things.

Precipitation of crystals occurs from a saturated solution when the temperature drops. Supersaturation can occur if there are no suitable nucleation points present, so you may want to consider how that may pertain to hastening the crystallisation process.

If you have warm naphtha, you would probably benefit by cooling it off using a cold water bath as temperature transfer to and from water is far more effective than with air. Be careful not to get water into the crystallisation dish!

Once the naphtha has cooled to room temperature or below you may be able to observe clouding of the solution - maybe even a few crystals if you're lucky. At this point, it may be possible to extend the cooling bath idea by using some kind of freezing-resistant liquid which you will have pre-chilled by placing it in the freezer before anything else.

Suitable liquids may include antifreeze (but be aware of its incompatibility with foodstuffs - take precautions against spillage!) or a strong calcium chloride solution. This latter one can be obtained easily from the single-use room dehumidifier packets, which liquefy into saturated calcium chloride solution after absorbing moisture from the air. You can throw the granules into some distilled water and filter off the impurities - mostly chalk and rust - and the resulting solution resists freezing down to -55°C when it is saturated, although calcium chloride will crystallise out as the temperature drops. (This crystallisation occurs in almost the exact same way as DMT crystallising out of naphtha.)

In the absence of calcium chloride, table salt will do but saturated brine will freeze at -22°C. You'll need to ensure that it's contained effectively should it happen to freeze solid.

If all this appeals to you, put the freezing bath in the freezer now, so that it's ready to receive your pre-cooled naphtha when you have that ready. You will need to ensure that your dish of naphtha can remain absolutely stable and not tip, slosh or spill in the freezer should you decide to do this.

One important footnote about heat-transfer baths is that one should, of course, always take displacement volume into account so that the coolant does not overflow when an item gets immersed in it.
Click to expand...

I have noticed the desire to grow larger crystals. Is this because larger crystals contain less oily residue?

Also, I'm curious about utilizing dry ice to lower the freezer temperature well below what a normal freezer goes. Would that speed up the process, or improve it any?
 
Faster crystallization results in mass nucleation starting everywhere; that traps impurities between rapidly forming crystals.

Crystallization and dissolution actually exist in a dynamic equilibrium. Stuff is continuously crystallizing and dissolving, the temperature only determines the proportions. As temperature fluctuates (and even if it stayed perfectly the same), some molecules are always breaking off crystals and floating away, while others float towards the crystals and "stick" to them. The crystalline lattice is always changing. Given enough time, that process tends to exclude impurities. It can take weeks for crystals to self-purify that way though, so it is much more efficient to crystallize them slowly the first time.
 
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I wonder if any research has been done to see whether an electrical current might influence crystal formation.

I don't have a background in chemistry or even fully understand the processes that I read here, but reading about positively or negatively charged molecules makes me wonder about electrical or magnetic influences. It would be cool if DMT crystals could be drawn toward something. :unsure:
 
Molecules with uneven charge distribution generally have what is called a dipole moment. Application of an electric field would cause alignment of dipoles, which could conceivably influence crystal formation. It could even give access to unusual polymorphs, perhaps if the EF was oscillating at a (radio)frequency [RF] which resonates with the molecule concerned. It would have to be a low energy [LE] field otherwise we'd just be warming up the molecules (like with microwaves) too much for crystallisation to occur.

Electrocrystallisation/electrocrystallization exists as a technique. Looking it up:

It seems mostly to be used for preparation of high-oxidation state metal oxides, but the LE-RF-EC idea is intriguing and requires some following up.

https://pubs.acs.org/doi/10.1021/cg800731p --> for protein structures
 
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