The Vespiary
The Hive => Newbee Forum => Topic started by: superman on August 05, 2004, 04:17:00 PM
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forgive me if this is redundant, but i've looked previously, and now again and can't seem to confirm my suspicion. when checking the ph of a water/xylene mixture, obviosly the water is on the bottom. if i remember correctly in high school they said to wet the ph papar and dip it into the np? this sounds wrong.....
how do i measure the aqueus layer through the np? do i have to empty it out and check then throw back into my sep. funnel?
thx, just about to work up my first (hopefully) success!
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You might use a nice pipette, dip it right through the nonpolar layer, and draw out a sample.
If you are extracting something, you might just wait until you have basified it properly before adding nonpolar.
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SWIM's just about to base my post rxn liquid. after basing the xylene should contain 1-1.5g meth. so i suppose then that SWIM would just drain some of the aqueuos layer from the separatory funnel and check it.
thx
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If you are doing an extraction or wash with a separatory funnel, just touch the stopper of the flask right after shaking to the pH paper (or indicator) and it should show you pH.
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Swip uses a 20ml syringe to get a PH sample beneath the non-polar solvent (meth base) ;)
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A syringe works well. Use thin plastic extender tubing and/or glass capillary tubes to reach the aqueous layer. If working with larger volumes, just tap off a small volume, measure, then pour back in. Its all about relative mechanical loss...
TIP - when lowering the syringe through the NP towards the aqueous, it will 'swallow' some NP up the tip. To overcome this, draw up the syringe a little before lowering so that when it is in the aqueous, you can squeeze the syringe to clear it. Then suck up the aqueous.