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Vacuum filtration techniques with Buchner or Hirsch funnels.

These are some tips to help you be more successful in collecting precipitate/crystals/powders etc.

  1. Record the mass of clean, dry filter paper. Why? Because oftentimes it is difficult to separate out the filter paper from your product. If you know the mass of the clean, dry filter paper, then you can subtract its mass.
  2. Record the mass of the “thing” you use to collect your product. That “thing” may be a watchglass, weigh-boat, crucible, beaker, dish, etc. You get the picture. IF you use a tape label, then make sure you weigh the mass of your watchglass (for example) WITH the label. Again, you can then subtract its mass later if needed. (E.g. if you screw up taring the balance).
  3. PRE-WET the filter paper in the funnel with the solvent (usually chilled solvent). This keeps the edges of the paper down so it won’t shift and won’t “float” up when you dump the solution into the funnel.
  4. Turn ON the vacuum BEFORE dumping a mixture into the funnel.
  5. DISCONNECT tubing from your filtration system; disconnect from the vacuum BEFORE turning off the vacuum.