Filtration and choice of solvent

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Discussion Overview

The discussion revolves around the challenges of filtering a solid precipitate from an unknown solvent and the implications of solvent choice on the filtration process. Participants explore the necessity of identifying the solvent before filtration and the appropriate methods to rinse the solid post-filtration.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether it is necessary to identify the unknown solvent before filtering the solid precipitate, suggesting the use of gas chromatography (GC) for identification.
  • Another participant proposes that if the solvent must be identified, and if multiple solvents are present, it may be necessary to mix those solvents for rinsing the solid during filtration.
  • One participant suggests alternative methods to filtration, such as using a syringe filter or centrifugation, but notes the unavailability of syringe filters in their case.
  • A later reply advises choosing a solvent that shares a common ion with the precipitate, providing an example involving silver chloride and silver nitrate.

Areas of Agreement / Disagreement

Participants express differing views on whether solvent identification is necessary before filtration and the best methods to handle the solid precipitate. The discussion remains unresolved with multiple competing approaches presented.

Contextual Notes

Limitations include the lack of information about the specific solvents involved and the potential impact of solvent choice on the filtration process. The discussion does not clarify the implications of mixing solvents or the criteria for selecting a rinsing solvent.

~christina~
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Another seemingly simple issue that I've never really had to think about before until now.

Say, I have to filter out a solid precipitate that I see in a limited amount of unknown solvent.

I have a Büchner funnel, but I need to have a solvent to rinse the solid with.

Questions I have about this
1. If I don't know what solvent it is, do I have to find out what it is before I filter out the
solid? (i.e. using GC)

2. If I have to find out the solvent through GC (I have to do this anyway) before I filter out
the solid, and the mixture consists of more than one solvent, do I have to mix the
solvents that are in the mixture and use that to rinse the solid through the filter with?

Thank you,
~christina~
 
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If all you are doing is a GC analysis, why don't you just use a syringe filter and be done with it? Or centrifuge and carefully decant with an eppendorf pipette?
 
chemisttree said:
If all you are doing is a GC analysis, why don't you just use a syringe filter and be done with it? Or centrifuge and carefully decant with an eppendorf pipette?
We don't have syringe filters at our disposal. They have just advised us today to decant the solid out and evaporate the solvent.

Thank you for your help,
chemisttree
 
i'd tell you to choose a solvent that does have a common ion with your precipitate..as example if you have AgCl you would use AgNO3 with it...and so on
 
Last edited:

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