Confusion About Vacuum Tubing & Connectors

[monster00]

The world of vacuum tubing and connectors is surprisingly complex for the newly initiated. With access to a complete vacuum chamber system, with a pump, jic fittings, a PTFE lined and stainless steel braided hose, and cold trap with a jic manifold, adding a glass filter flask does not seem so simple.

What's the standard way that tubing is connected to a glass flask with glass hose barb side arm?

I assume there needs to be a transition somewhere from the stainless steel jic fittings and heavy stainless steel hose to the fragile glass arm. Is the accepted method to use a different, softer hose material from the trap to the flask? Or can the stainless steep braided hose work somehow? If the hose has to change to something softer, what hose is ok to use with hydrocarbons and has sufficient external protection in lieu of PTFE lining with stainless steel braiding?

There's also a whole industry of fitting types and proprietary fitting systems out there, such as Swagelok, Ace-Safe, JIC, NPT, etc. Is there an affordable and accessible option for the non-lab professional?

Is there something I'm missing about this and it's actually way easier to connect a filter flask to a vacuum pump system?

 

[downwardsfromzero]

You'll need to terminate the vacuum hose with a push-on hose barb, something like:

then use thick rubber vacuum tubing to connect to the glass spigot. Prudence dictates the use of a trap to counter suck-back, and if you are filtering anything other than water your cold trap is particularly invaluable. Does your trap require LN₂ or is it otherwise refrigerated? And what type of vacuum pump are we talking here? Sounds like you have a versatile setup in the making there.

 

[monster00]

You'll need to terminate the vacuum hose with a push-on hose barb, something like:

then use thick rubber vacuum tubing to connect to the glass spigot. Prudence dictates the use of a trap to counter suck-back, and if you are filtering anything other than water your cold trap is particularly invaluable. Does your trap require LN₂ or is it otherwise refrigerated? And what type of vacuum pump are we talking here? Sounds like you have a versatile setup in the making there.

Thank you for clarifying that for me!

It will be used in filtering with organic solvent.

The trap can used with nitrogen or dry ice:
1.5 gallon cold trap

Here's the hoses or tubing I have:
stainless steel ptfe 1/4 jic hose

The pump is a 6 cfm 2 stage spark free vacuum pump

Versatility is one of the main goals. I'm all ears if you have anything else to add regarding a versatile vacuum system for extractions, work-ups, and crystallization.

 

[downwardsfromzero]

If you're using LN₂ in the cold trap, I hope you know never, ever, EVER to draw air through the trap because this will lead to the condensation of liquid oxygen which in contact with residues of flammable solvent or even merely combustible substances can cause a catastrophic explosion.

On a less dramatic note, don't expect a strong vacuum to be the magic fix for all filtration problems. A clogged filter is a clogged filter and pulling harder doesn't change that. For some things patience is the only cure

One more tip: watch out when pulling low-boiling solvents since evaporative chilling can lead to crystallisation of the product in the neck of the funnel.

 

[monster00]

If you're using LN₂ in the cold trap, I hope you know never, ever, EVER to draw air through the trap because this will lead to the condensation of liquid oxygen which in contact with residues of flammable solvent or even merely combustible substances can cause a catastrophic explosion.

On a less dramatic note, don't expect a strong vacuum to be the magic fix for all filtration problems. A clogged filter is a clogged filter and pulling harder doesn't change that. For some things patience is the only cure

Thankfully I was only planning to use dry ice. Now, I plan to very actively avoid LN₂. Lol.

Great tip about the clogged filters. I recently acquired some proper skills with gravity filtering and hot filtration. It's amazing how much better filtering can be when done correctly. Thanks

 

[monster00]

If you're using LN₂ in the cold trap, I hope you know never, ever, EVER to draw air through the trap because this will lead to the condensation of liquid oxygen which in contact with residues of flammable solvent or even merely combustible substances can cause a catastrophic explosion.

On a less dramatic note, don't expect a strong vacuum to be the magic fix for all filtration problems. A clogged filter is a clogged filter and pulling harder doesn't change that. For some things patience is the only cure

One more tip: watch out when pulling low-boiling solvents since evaporative chilling can lead to crystallisation of the product in the neck of the funnel.

How do you minimize the crystallization caused by evaporative cooling? I plan to use hexanes and heptane with this.

 

[downwardsfromzero]

How do you minimize the crystallization caused by evaporative cooling? I plan to use hexanes and heptane with this.

What are you doing that necessitates filtering naphtha? Heptane/hexane wouldn't be so much of a problem; I was more thinking acetone, DCM, ether. The trick is to pull the minimum necessary vacuum to achieve a reasonable flow rate. Use a reducing valve between the pump and the filter setup. An air bleed would be undesireable if you were using LN₂ in the cold trap.

And, arguably, your setup could be considered excessive for simple filtration. An aspirator would do the job. This means you're obligated to do some vacuum distillations and sublimation

 

[monster00]

How do you minimize the crystallization caused by evaporative cooling? I plan to use hexanes and heptane with this.

What are you doing that necessitates filtering naphtha? Heptane/hexane wouldn't be so much of a problem; I was more thinking acetone, DCM, ether. The trick is to pull the minimum necessary vacuum to achieve a reasonable flow rate. Use a reducing valve between the pump and the filter setup. An air bleed would be undesireable if you were using LN₂ in the cold trap.

And, arguably, your setup could be considered excessive for simple filtration. An aspirator would do the job. This means you're obligated to do some vacuum distillations and sublimation

The plan is to utilize vacuum filtration during the crystallization process, so washing and drying in a buchner funnel.

I originally planned on purchasing the type of aspirator that connects to water faucet for this, thinking it would be a simple, safe, and effective way. Then I thought that maybe instead of spending money on aspirator valves and connections, why not use the vacuum equipment I already have? And that is what lead to all this.

While I'm still here with all these disconnected hoses and uncompatible parts, I'm afraid vacuum distillation and sublimination is a consideration for the distant future. Baby steps.

 

[downwardsfromzero]

[Tip for using aspirator: use an aquarium water pump to circulate the water in a closed system (e.g. storage tub). This saves water and also allows you to contain contamination of the water flow.]

I've never needed to suction filter freeze-precipitated DMT as it has always stuck to the dish. The few free-floating crystals were always captured easily with decanting and pipetting. At least the evaporative cooling issue won't be relevant to this particular use-case, although you may have to watch out for ice from atmospheric water vapour.

 

[surquillo]

[Tip for using aspirator: use an aquarium water pump to circulate the water in a closed system (e.g. storage tub). This saves water and also allows you to contain contamination of the water flow.]

I've never needed to suction filter freeze-precipitated DMT as it has always stuck to the dish. The few free-floating crystals were always captured easily with decanting and pipetting. At least the evaporative cooling issue won't be relevant to this particular use-case, although you may have to watch out for ice from atmospheric water vapour.

Pool pump 5L /min 12DC are cheap. One could use that indeed with a large bucket where the hose goes in and the T split. I use 8mm hose for suction and 16mm for pumping. Very quiet system. Good advice downwardsfromzero :thumb_up:

 

[monster00]

[Tip for using aspirator: use an aquarium water pump to circulate the water in a closed system (e.g. storage tub). This saves water and also allows you to contain contamination of the water flow.]

I've never needed to suction filter freeze-precipitated DMT as it has always stuck to the dish. The few free-floating crystals were always captured easily with decanting and pipetting. At least the evaporative cooling issue won't be relevant to this particular use-case, although you may have to watch out for ice from atmospheric water vapour.

Here's what I had in mind:

The collecting and washing step in this video:

From the MIT Chemistry Techniques videos in this thread: Learn useful chem techniques from MIT videos - FAQ - All your basic questions and answers - Welcome to the DMT-Nexus