EugeneOregon
New Member
I have learned that the use of polymers in my vacuum system needs to be kept to an absolute minimum. Lolz, like everything else I had already ordered $17 per foot premium Nalgene vacuum line before I learned this.
To be fair I am very glad I have the Nalgene. It is a DREAM to work with and it is worth every penny, but now I only use it to couple metal to glass in inch size pieces.
Any polymer I have learned is simply too permeable to operate in molecular distillation deep vacuum applications without leakage. My understanding is that even the o rings in the seals leak. The explanation is sort of the same deal as a helium filled balloon from the fair. The balloon will lose enough gas in one day through permeability to lose bouyancy because the pores in the rubber compound are big enough to let small helium atoms through. The same apparently with Nalgene in that it has enough permeability to allow enough small molecules through to impact deep vacuum attempts.
I have seen the vacuum gauge jump 100 microns when I forget to turn on the stir bar and then turn it on after things are 60C as measured. It pulls down again but it is obvious that at under one micron it takes VERY little extra gas present in the system to impact deep vacuum significantly. Being old enough to make most mistakes twice and three times at least, I have seen glass fail from my own stupidity. I respect the enormous pressures involved with deep vacuum. I employ a full spherical mantle for the efficiency while at the same time I enjoy the safety of having all the really hot stuff and glass (most likely implosion point) encapsulated in thick mat. A full spherical mantle in this regard is a great safety device. Inspecting each bulb takes only a moment and any cracks at all are grounds to toss the unit into the trash.
From experience let me pass on little tips. I always leave at least one joint unclipped but secured otherwise. In the case of an unexpected presurization (like a small pocket of water going superheated and making a small explosion in the flask) then the unclipped joint allows a point of pressure relief in a predictable location which is made safer. On my bulb set up I leave the fritted air inlet adapter on the end unclipped for this relief now. It will just pop off but is only connected by a few inches of Nalgene so nothng is broken. Once implosion or overpressurization breaks the vacuum the boiling ceases instantly. The next tip is this - NEVER peer at the process from directly over any glass joint. I made the mistake of restarting hot extract while still purging residual solvents after a short shut down. During he shut down the stir bar was stopped. Upon restarting the vacuum the gas that evolved instantly overpressurized the boiling vessel which then took on what looked like a whale clearing his breathing hole lolz! I learned that my Amish built dining table has an EXCELLENT finish against hot extract that sponges up easily lolz. There was even extract in my coffee mug. It got on everything on the table. If it had got into my eyes.... just rub your eyes after touching standard extract...ouch! I also "aim" every single opening that might fail this way in a direction away from my chair.
Thank you again for indulging me and offering a place for this information.
To be fair I am very glad I have the Nalgene. It is a DREAM to work with and it is worth every penny, but now I only use it to couple metal to glass in inch size pieces.
Any polymer I have learned is simply too permeable to operate in molecular distillation deep vacuum applications without leakage. My understanding is that even the o rings in the seals leak. The explanation is sort of the same deal as a helium filled balloon from the fair. The balloon will lose enough gas in one day through permeability to lose bouyancy because the pores in the rubber compound are big enough to let small helium atoms through. The same apparently with Nalgene in that it has enough permeability to allow enough small molecules through to impact deep vacuum attempts.
I have seen the vacuum gauge jump 100 microns when I forget to turn on the stir bar and then turn it on after things are 60C as measured. It pulls down again but it is obvious that at under one micron it takes VERY little extra gas present in the system to impact deep vacuum significantly. Being old enough to make most mistakes twice and three times at least, I have seen glass fail from my own stupidity. I respect the enormous pressures involved with deep vacuum. I employ a full spherical mantle for the efficiency while at the same time I enjoy the safety of having all the really hot stuff and glass (most likely implosion point) encapsulated in thick mat. A full spherical mantle in this regard is a great safety device. Inspecting each bulb takes only a moment and any cracks at all are grounds to toss the unit into the trash.
From experience let me pass on little tips. I always leave at least one joint unclipped but secured otherwise. In the case of an unexpected presurization (like a small pocket of water going superheated and making a small explosion in the flask) then the unclipped joint allows a point of pressure relief in a predictable location which is made safer. On my bulb set up I leave the fritted air inlet adapter on the end unclipped for this relief now. It will just pop off but is only connected by a few inches of Nalgene so nothng is broken. Once implosion or overpressurization breaks the vacuum the boiling ceases instantly. The next tip is this - NEVER peer at the process from directly over any glass joint. I made the mistake of restarting hot extract while still purging residual solvents after a short shut down. During he shut down the stir bar was stopped. Upon restarting the vacuum the gas that evolved instantly overpressurized the boiling vessel which then took on what looked like a whale clearing his breathing hole lolz! I learned that my Amish built dining table has an EXCELLENT finish against hot extract that sponges up easily lolz. There was even extract in my coffee mug. It got on everything on the table. If it had got into my eyes.... just rub your eyes after touching standard extract...ouch! I also "aim" every single opening that might fail this way in a direction away from my chair.
Thank you again for indulging me and offering a place for this information.
