Buchner funnel grit/porosity size

[BrownRiceSyrup]

One would assume that the finer the grit the better. But having 0 experience with it, does it really matter? Does it slow down the filtering process significantly to get a fine frit (15-40 Micron) versus a medium frit (40-80 micron)? If not, then do i assume to get the fine grit? Of course my focus is general o-chem/clandestine stuff...

 

[Zarder]

I find that the in larger grit I get quite a bit of product stuck in the filter paper. Which I can extract with solvent. It’s just extra work and I prefer finer grits.

 

[BrownRiceSyrup]

youre saying that with the coarse grit you get more stuck than with finer grit? fascinating. You'd think it was the opposite. I could see that though, more surface area for the stuff to get caught in. Does it make a difference in the speed of filtration? is it negligible and who cares, or does it even matter?

 

[Zarder]

It doesn’t make much difference for me in terms of speed of filtration. Just filter for a couple of minutes longer.

 

[BrownRiceSyrup]

thanks man!

 

[G.Patton]

Hi, depends on your filtration scale. I would recommend you to use 40-80. You can control filtration by a filtration paper pore size. Also, I recommend to use Shcott filter to small scale.

 

[Osmosis Vanderwaal]

A related question, how much vacuum should I use? I was playing with my Buchner funnel and I cranked it to -15 psi and the water coming through the frit turned to foam. I wasn't expecting that. I'm not sure if it was because I was using a piece of brown paper sack for a filter paper or if it was because I don't even consider washing the funnel before I used it the first time. Or if the reason was using too much vacuum. I was filtering cocaine HCl in water, trying to remove insoluble adulterants.

 

[Zarder]

If it’s foaming that normally means it is boiling. Use less vacuum.

 

[Osmosis Vanderwaal]

It would be odd for water to boil at room temperature and -15 psi. Seems water might boil at 174°f, just doing the math in my head. That is something I hadn't considered though. I don't know why the gauge has+ and - psi, but sounds ridiculous to say -15psi. I guess that should be+-0 A PSI, since air pressure is (when I'm calculating pressure ie theoretical) 14.7 psi at sea level