1. Schlenk Line Techniques
Liquid N2

2. Dangers GLASS UNDER HIGH VACCUM
FIRST AND CONSTANT DANGER IS IMPLOSION !!!
Check glassware for faults before use. NEVER use a piece presenting any damage even the tiniest one.
Always protect yourself from a potential implosion
Be extra-careful with large flask (250mL or more) – be sure they are tightly secure before vacuum them
Dewar are also made of glass under very high static vacuum  shock will result on violent implosion

3. Dangers Explosion – liquid oxygen Prevention:
NEVER ‘vacuum’ air or any gas (buchner filtration should never be performed using vacuum line)
Monitor any suspicious sound from the pump and condensation around the dewar
If it happens:
DO NOT seal trap – DO NOT warm up
Shut down the pump but leave the Liquid N2
Place blast-shield in front and sash down
Close line/trap tap, leave trap/vacuum open
EVACUATE THE LAB and seek assistance
Only if it is safe for you !

4. Dangers 2 Explosion – Nitrogen pressure
Always be aware of your working pressure – Do not use more than mbar
Be always sure of where the flow goes (= bubbler monitoring)
In general - do NOT heat a sealed system (never with Et2O / DCM)
Do not close (entirely) your bubbler
Check regularly your set-up for loose parts.

5. Setup Glass taps Numbered taps only
Check/re-grease regularly (but do not over-grease)
Young’s taps
Don’t overtighten
White ‘ring’ is sufficient
Vacuum
1x1O-1 ok
<5x10-2 good
YES NO

6. Setup Trap Protects the pump from solvent vapours
Not designed for solvent evaporation ! (trapping efficiency is complete  solvent will reach the pump and can start a fire)
Should be always immerged in liquid N2 when working with the line
NEVER warm a cold trap without an opened exhaust
Be careful with thermal shock and dewar manipulation

7. General Use
Shut down
Seal trap from vacuum, remove liquid N2, remove the trap
(Turn off pump)
Reduce/Shut-down N2 at regulator
Check taps are open/closed as appropriate
NEVER leave the lab with a line on (at least without a good reason…)
Glassware
Dry glassware first in oven – assemble quickly and cool under vacuum
At least 3 Vacuum/N2 cycles to remove air from tubes before opening Schlenk tap
Use rubber bands/clips on lids if under N2
Don’t place under vacuum with subaseal on unless they are new!

8. Solvent Removal Solvent removal:
Use intermediate N2 trap if the volume to be removed is more than traces.
Close Schlenk tap, then open line to vacuum
Open Schlenk tap slowly with vigorous stirring
Tilt Schlenk 45 degrees with stirring to decrease bumping
DON’T leave it assuming it’s fine unless small amount of solvent left

9. Solvent Transfer Syringe Check syringe/needle joint
Flush syringe with N2 3x before withdrawing solution
Use syringe twice as big as volume withdrawing
Keep syringe inverted during transfer – N2 at top
Consider cannula over mL, especially with pyrophorics

10. Solvent Transfer Cannula: Metal for pure solvent , PTFE for solution.
Set up first, then take cannula from oven and use straight away
Place into starting Schlenk and blow N2 through for a second or two
Place other end into receiving Schlenk
Place needle (eventually connected to a second bubbler) in receiving Schlenk and close it N2 supply
Wash cannula with acetone/water/dilute HCl twice if solution used
needle outlet
N2 closed
N2 open

11. Solvent Transfer Cannula transfer from sureseal to ampoule
Pierce sureseal with needle connected to N2 line
Cut off syringe end and place in tubing to do this
Carry out cannula transfer as described before
Use measuring ampoule if volumes important

12. Cannula filtration Remove gloves – PTFE tape very static
Place PTFE tape around end (metal)
Fold dried filter pad (from oven) over end
Wrap around with PTFE tape until sealed on
Leave exposed filter at top
Place back in oven for a few minutes
Pierce underside of subaseal and feed through

13. Freeze/Thaw Solvent Degassing
Safety - carefully check glassware for cracks
- do not fill the ampoule > 60%
- ensure that Young’s tap creates an effective seal
- use a vacuum gauge
- never open the ampoule to argon during freezing
General
Freeze solvent with liquid N2 dewar
Quickly open/shut vacuum to apply partial vacuum as it is freezing
Place under vacuum (monitor with a vacuum gauge to good steady vac)
Close vacuum and remove ampoule from liq N2 – leave tubing under vac and be aware of vac gauge in case of any leak.
Keep the fume cupboard sash lowered as far as possible whilst warming
Repeat x3 for general needs
Refill with N2/Ar when at room temperature when finished

14. Distillations Under Nitrogen Under reduced pressure Bubbler open!
Assemble (dried) glassware then heat under vacuum
Under reduced pressure
Use pressure gauge to regulate pressure
Connect distillation to vacuum
Distill under static vacuum
(top up vacuum if necessary)
Grease free trap to trap setup
To wash up rinse with base bath/acid bath/acetone but be careful of o-rings. Do not put in the oven (heat gun before use)

15. Summary
Check for videos on most techniques (narrated in German but still easy to follow)
Ask if you aren’t sure!