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Purification and freeze precip questions

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When doing sodium carb wash, any difference between running the na2co3 solution through saturated naphtha vs simply running it through the dry crystals?

When doing a mini-A/B, what is the difference between salting alkaloids out of the NPS vs directly dumping the dry crystals into an acidic solution? @Orion

When removing the crystal dish from the freezer to decant the NPS, could it help prevent crystals from melting back into residual solvent if I float the naphtha above the crystals (with water) before decanting? Assuming the crystals aren't swimming and the water doesn't freeze. Would the water affect the crystals besides extending the drying time?
 
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Icon said:
When doing sodium carb wash, any difference between running the na2co3 solution through saturated naphtha vs simply running it through the dry crystals?
Click to expand...
Washing the saturated naphtha sounds like the more sensible option to me - this helps remove base droplets benore the freeze precip. Washing the crystals esssentially means they'll get superficially contaminated with Na₂CO₃.
Icon said:
When doing a mini-A/B, what is the difference between salting alkaloids out of the NPS vs directly dumping the dry crystals into an acidic solution? @Orion
Click to expand...
Either will do. Redissolving them in clean NPS could count as an extra purification step, but it's not strictly necessary.
Icon said:
When removing the crystal dish from the freezer to decant the NPS, could it help prevent crystals from melting back into residual solvent if I float the naphtha above the crystals (with water) before decanting? Assuming the crystals aren't swimming and the water doesn't freeze. Would the water affect the crystals besides extending the drying time?
Click to expand...
The crystals might well float, plus warming from the water may cause some redissolution into the NPS. Consider also that many people go to considerable lengths to prevent condensation in the dish, so adding water is unlikely to be a great idea (although I've not tried it myself in this exact context).
 
I can see why condensation might be good to avoid, what with co2 dissolving into the micro droplets. Maybe a pinch of sodium carbonate would do the trick. When I was washing my dry crystals in sodium carbonate solution they seemed 100% hydrophobic. It was like they weren't even wet, flying around in suspension as individual grains, like a snowglobe. But they did want to float above the water, so that could disrupt the adhesion of the crystals to the dish.

Transform said:
Washing the saturated naphtha sounds like the more sensible option to me - this helps remove base droplets benore the freeze precip. Washing the crystals esssentially means they'll get superficially contaminated with Na₂CO₃.
Click to expand...
That would only be applicable if I'm re-using the solvent though right? I guess people normally do a sodium carbonate wash on their hot pulls before freeze precipitating? I forgot to.

I did the Na2CO3 wash on dry crystals - didn't appear to remove anything. Then I washed with distilled water to pickup the superficial Na2CO3 contam, which was apparently overpowered by dissolved CO2. Either way, the sodium carbonate wash was probably redundant since I intended to do a mini-a/b immediately after.

How do you type the miniature numbers for molecular formula?
 
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Icon said:
How do you type the miniature numbers for molecular formula?
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I use a personalised keyboard layout!
'Unexpected keyboard' is a great FLOSS option for android phones.

We used to have "sub" and "sup" BB code tags to type in the edit window. If they don't work any more, the subscript at least can be approximate by choosing a smaller font size. (It works!)

Test: CO2
Code: 
 CO[sub]2[/sub]

Yep, that works!
 
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