RogueRose
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Registered: 16-6-2014
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Need 2" stopper (tapered rubber/silicone) for HNO3 and NH3 (both in hot gaseous form)
I have a SS distillation apparatus and the end of the column has a rubber bung/stopper (with hole for thermometer). This is fine for ethanol and most
essential oils but I don't think it will stand up to gaseous ammonia or nitric acid (both being distilled).
The column isn't going to be under pressure but it still needs to hold in place. The OD is 2" and ID about 1.9" or so.
I was planning on making a tapered silicone stopper (from RTV caulking type silicone) but it looks like this wouldn't be resistant to either substance
at the temps needed fro distillation. I was hoping to make something from items on hand for a temp fix but I'm not sure what would be suitable for
this.
I do have some 1/4" PVC which could be stacked and then shaped into a stopper and it seems that this may be suitable for HNO3 and NH3 though it
doesn't state temps in this chart.
http://www.aleco.com/chemical-chart.html
another option I was thinking which is a little unconventional is using wood (Oak, cherry, maple, black walnut, pine, MDF, press board and plywood -
are available). The temps should be fine but I'm not sure if it would contaminate the gases at all.
What would be the ideal material for this stopper once I finally order one? I can get thick HDPE, LDPE, UHMEPE, graphite, may possibly be able to
order a piece of PTFE (1" thick by 2" x 2" square..?) or I may be able to have a glass maker make a Boro stopper but I'd have to drive up to see him
and do it.
Any suggestions for an immediate solution and thoughts on a more permenant option?
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Deathunter88
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Location: Beijing, China
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Quote: Originally posted by RogueRose  | I have a SS distillation apparatus and the end of the column has a rubber bung/stopper (with hole for thermometer). This is fine for ethanol and most
essential oils but I don't think it will stand up to gaseous ammonia or nitric acid (both being distilled).
The column isn't going to be under pressure but it still needs to hold in place. The OD is 2" and ID about 1.9" or so.
I was planning on making a tapered silicone stopper (from RTV caulking type silicone) but it looks like this wouldn't be resistant to either substance
at the temps needed fro distillation. I was hoping to make something from items on hand for a temp fix but I'm not sure what would be suitable for
this.
I do have some 1/4" PVC which could be stacked and then shaped into a stopper and it seems that this may be suitable for HNO3 and NH3 though it
doesn't state temps in this chart.
http://www.aleco.com/chemical-chart.html
another option I was thinking which is a little unconventional is using wood (Oak, cherry, maple, black walnut, pine, MDF, press board and plywood -
are available). The temps should be fine but I'm not sure if it would contaminate the gases at all.
What would be the ideal material for this stopper once I finally order one? I can get thick HDPE, LDPE, UHMEPE, graphite, may possibly be able to
order a piece of PTFE (1" thick by 2" x 2" square..?) or I may be able to have a glass maker make a Boro stopper but I'd have to drive up to see him
and do it.
Any suggestions for an immediate solution and thoughts on a more permenant option?
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Just wrap your existing rubber stopper with some PTFE plumbers tape. Make sure there are no gaps and you are good to go.
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Sulaiman
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Is stainless steel compatible with nitric acid ?
If you are distilling near-anhydrous HNO3 then I guess the ss would be passivated,
but I think that hot dilute nitric acid will eat ss.
CAUTION : Hobby Chemist, not Professional or even Amateur
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RogueRose
International Hazard
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Registered: 16-6-2014
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| Quote: Originally posted by Sulaiman | Is stainless steel compatible with nitric acid ?
If you are distilling near-anhydrous HNO3 then I guess the ss would be passivated,
but I think that hot dilute nitric acid will eat ss. |
The concentration will be less than 30% and from the few tables I checked it said that this was fine for the grade SS I had, even at high temps. The
problem is that each chart listed many of the same materials and there was conflict between them and whether they are adequate with various chemicals,
so I have to do some more research into the nitric acid issue before hand.
I have some Teflon non-stick spray (only ingredients are the propellents and petroleum distilllates, doesn't mention PTFE though..) I found the MSDS
for the product and it doesn't mention PTFE in it anywhere! I'm wondering if a couple coatings of this long the pipe and inside of the vessel would
allow for more or adequate protection from the HNO3?
Attachment: DuPont Non-Stick Dry Film Lubricant Aerosol_US GHS SDS_English_15_April 2015.pdf (194kB)
This file has been downloaded 453 times
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Melgar
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Registered: 23-2-2010
Location: Connecticut
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Closed-cell LDPE foam actually works pretty good for this and it's easy to find. I rolled this up and covered it with heat shrink once, and it worked
surprisingly well. RTV silicone can make a decent stopper, but the trouble is that the surface is slippery against glass and often polished metal as
well.
Another option is you just get some vinyl tubing of various diameters and put them one inside the other. Or you get a really durable, rigid material
for the inside, then cut a piece of vinyl tubing that you can push over that when it's soft. Will it hold up for very long? Of course not, but it'll
hold up for a single distillation, and two feet of vinyl tubing is cheap enough that you can just cut off a new piece every time you need to do
another run and/or your last piece doesn't look like it'll last much longer.
edit: I used to have trouble with my thermometer gaskets always failing, until I got the idea to just cut thin slices off of a piece of vinyl tubing
every time there was a failure, or a failure looked imminent. Also, during the distillation, I think what happens is that NOx and other nitrogen
species end up being absorbed by the gasket material, and discolor it. This doesn't affect its structural integrity immediately, but those things
will stay in there, breaking it down gradually over time. Thus, even though you do expect it to fail eventually, if you cut a new piece each time, it
probably won't fail during any of your distillation runs.
[Edited on 10/22/17 by Melgar]
The first step in the process of learning something is admitting that you don't know it already.
I'm givin' the spam shields max power at full warp, but they just dinna have the power! We're gonna have to evacuate to new forum software!
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