Nitrogen Backfilling - Techniques, Tools, Talk

Hello friends!

My name is Graham and I’m lab manager in CO. My team does BHO extraction and distillation. In an attempt to eliminate oxidation I have been using nitrogen to backfill the containers holding my distillate. I would like to start backfilling my unit with nitrogen instead of air during switches and even use it during the punch and other processes like mixing carts and capping round bottom flasks.

I’d like to start a dialog about nitrogen uses and the glass fittings that make it the most feasible. How many of you currently use nitrogen on a regular basis? where do you use it?

Does anyone have a good source for a cheap 24/40 glass fitting that has a two hose barbs? i need a nitrogen inlet and an air outlet.

What’s the best container/fittings to use to flow nitrogen over a decarb or when mixing terpenes into distillate? I typically use a large or small beaker for these operations. Should I make a lid? is there a better way!? Someone please enlighten me.




For inert gas and vacuum on a lab bench use shlenk lines, they are a purpose build for what you want. You’ll want to centralize your bottles too. Find a good spot for your gas storage, make sure it has chains to hold the bottles from falling. Use compression fittings, and stainless tube to pipe it around the lab to the locations it will be used. Put a flow meter at the end of the tube to control it’s flow. This way one tank with a regulator can be used in multiple locations at the same time.
Helpful inert gas techniques include:
1)Bubble with gas wand during decarb.
2) filling of appreratuses with inert gas.
3) Blow down evaporation of small samples.
4) sweeping vacuum oven atmosphere
5) assist gas in closed loop
6) liquid transferring
7) flash cromatography

One thing to keep in mind, nitrogen gas tanks don’t have any liquid in them. The first 500 psi will come off a k sized cylinder the fastest, the last 500 psi will take a few days. I like to have argon on hand as well, it displaces air better because if it’s weight. I feel this last’s longer in packaging.


Is this the item you wanted?

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Yes! Thank you.

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This is from the @LabSociety Blog entry on nitrogen backfilling


Hi Graham,
I have had extensive experience as an inorganic chemist in methods for excluding oxygen. I am a big fan of nitrogen or argon back-filling and am hoping to develop and test methods for doing so in the distillation process. At this point all I have are ideas. Below are some thoughts:

  1. No need for an air out, you can use your pump to move the atmosphere - it uses up less nitrogen than purging. What you do is pump down the system to baseline vacuum, then close off the pump valve and back-fill the system with nitrogen. If you do this 3-5 times you will have reduced the oxygen content dramatically.

  2. I was thinking of using the thermometer port of the boiling flask as the inlet source of N2 for purging. There are two parts I found on Amazon that could do this:
    Precision 24/40 With Hose Connection Inlet Thermometer Adapter or Kimble Chase ADAPTER THERMO ST 24/40 Offset Thermometer Inlet Adapter with Hose Connection.
    With these two you would need to hook up an inline valve in a hose connecting the niple to your nitrogen tank (this could potentially introduce a leak point).
    You could also put this adapter (AF-0500 - ADAPTERS, CONNECTING, AIRFREE®, SCHLENK- Chemglass Life Sciences) in between your thermometer adapter and the boiling flask.

  3. Has anyone thought about using a nitrogen bolus to chase out head vapors before bringing over main body?

Hope this helps out. I am very interested in seeing what others are doing regarding nitrogen purging.



slick! the bubble check valve is a smart idea.


Sparging with n2 during the process could carry moliclues past cold traps. If used during the main body of the distillation it may mix fractions by upsetting the qulibrium in the fractional column. Basically lowering the theroetical plate count. I guess if you wanted to use it to rip everything off the crude you could possibly get it would work.


Yeah those check valves are sexy (and spendy), but IMHO the check-valve bubble system is useful only if you are really worried about over-pressurizing your system. A good 2-stage regulator on your N2 tank and an appropriate 2nd stage pressure will mitigate this.

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Agreed, I was thinking only for the heads and not the main body.

That’s what i was planning to do. Regulate at the tank and then have a pressure bleed somewhere.

Well sometimes I’ll do a heads cut that takes a long time, so i’ll want to cool down the system and clean the head and reset. I’d like to backfill with nitrogen during this step. so the load flask is 220C and the vacuum is running… I’d like to introduce low pressure nitrogen somewhere near the pump to let the system down to atmospheric pressure without introducing oxygen.


Use a low flow meter and two stage reg


I asked this in the other nitrogen backfilling thread, but i wanted to ask it here as well.

What kind of safety precautions are necessary for using the nitrogen backfill since N2 is an oxygen displacer? Does it have to be as ventilated as a room for butane (obviously not), but looking for sound advice so i can impliment this in my lab. Is an O2 sensor necessary?

My primary use would be for backfilling ovens.

Will u show me a pic of ur lab frame please?!

I’d say no sensor is needed and n2 is fairly safe to implement ime

Does anyone have a picture of the nitrogen backfill system set up to their ovens?