Cheap Vacuum Pump

[wymanthescienceman]

OK, first off I wanna let you know that since I want to use this for HNO3, that I think it belongs in this section. I've used the search engine but couldn't find anything about using one of these.

I recently bought myself a Foodsaver vaccum preservation system for vacuum sealing foods, and I dont really have any more use for it so I was wondering if I could use it as a vacuum pump for distilling HNO3. I cracked that baby open and found it was surprisingly simply built. (See pic #1) Low and behold it uses a very simple pump for removing air from the bags. I have a few questions about maybe using it as a possible vacuum pump for the distillation of HNO3.

First, do you think it can pull enough of a vacuum to distill? It looks as though it has a switch (The round red thing, See pic #2) that automatically kicks in the heat strip for sealing the bag at a certain vacuum. The switch reads -500mbar and the only reason it is there is for activating the strip when it reaches its max vacuum, it can easily be removed from the system if need be as I doubt the pump will create enough vacuum to implode a flask. The pump itself can create enough vacuum to crush a soda can, and thats about the only way I have to tell the vacuum it pulls because I dont have a vacuum gauge.

Second, the pump and piston is made of some type of plastic (See pic #3), I'm not exactly sure what kind, but the piston has a rubber gasket which is obviously a no no for hot HNO3 vapor, so if I were to use this, any vapors or NOx gases would have to be removed or greatly reduced. So what would be my best bet for this? I thought about having a sodium bicarbonate solution to filter out these gases, or some other type of substance in-line to remove the vapor before it reaches the pump and destroys it.

If anyone has gotten one of these to work for distilling, please let me know how it worked out. I'm up for any suggestions to get this to work because I can't spend over $200 for a vacuum pump. If you need more info about it I can try to answer your questions.

Pic #1 http://www.roguesci.org/theforum/attachment.php?attachmentid=858&d=1170298211

Pic #2 http://www.roguesci.org/theforum/attachment.php?attachmentid=859&d=1170298211

Pic #3 http://www.roguesci.org/theforum/attachment.php?attachmentid=860&d=1170298211

UPDATE: While doing a bit of browsing after looking at the vacuum switch I came across a vacuum table. I found out that if that switch indeed works when the pressure drops by 500 mbar, then the vacuum pump must pull close to a 400mm Hg vacuum, but NOx are usually removed from HNO3 at around 200mm Hg for 10-30 min according to Wiki. After seeing this I decided to check out boiling points for HNO3 at reduced pressures and came across a boiling point calculator. At 400mm Hg HNO3 will boil at approximately 66-68C, down 15-17C from its atmospheric BP of 83C. Would this reduced BP allow me to distill good HNO3 without excess NOx, or would I need a higher vacuum to do it correctly? I've tried to distill HNO3 at atmospheric pressure but it doesnt work well. It's very slow and I can't do it in cold weather. I'm thinking that even though the vacuum I may be able to create isn't enough, it will give me a somewhat decent HNO3, compared to what I got before. All I want is clear HNO3 at a concentration of 70% or higher.

What do you guys think? Am I way off?

[Alexires]

Good one wyman, I understand your pain of not being able to buy a vaccum pump.

First off, there isn't "enough of a vaccum to distil" per'se for HNO3. ANY vaccum is a good vaccum in this case. Since people have been known to distil clean nitric at STP, the reduction of 15*C in bp will work well for HNO3. If you don't know how far exactly your pump draws down to, a suggestion is to attach it to a flask and put some DISTILLED (important) water in there and see at what temperature that boils. That will tell you what kind of reduced pressure is in there. This will let you calculate the bp of HNO3 at that pressure.

Nextly, hot HNO3 vapors + anything is bad. Glass works, but things like plastic, PVC, workbenches, hotplates, skin, etc aren't good things to mix with it. To make sure you don't get that in your vaccum pump, you will want a vaccum trap or 3 hooked up between your vaccum adaptor (attached to your receiving flask ofcourse) and your pump. Fill 'em with Bicarbonate solution and you should be pretty ok.

On the matter of if your flasks can take the pressure. As I understand it, if a flask is rated for vaccum operation it shouldn't matter how low the reduced pressure gets (even to a "total" vaccum) the flask will keep together.

If you are unsure whether your flask can take the pressure you can

1) Ring the maker and ask them. Make sure you get the right model, etc.
2) Buy some stuff you know is capable of operating at reduced pressure, or
3) Hook the flasks up to the vaccum pump, hide behind a wall where you can turn the vaccum pump off without getting inline for shapnel and turn the sucker on.

Remember, glass shrapnel is bad for your happiness.

A couple of other tips, when you are distilling nitric under vaccum, don't use a bunsen burner to heat it, don't use a water bath (a whole bunch of hot nitric + water = pain). Use an oil bath, keep the temperature as low as possible while still getting some distillate and that will keep it nice and free from NO2.

Can't think of anything else, so other than that, good luck and tell us how it goes!

[aikon]

www.frogfot.com

You'll find a DIY vacuum pump there made totally out of hardware stuff.

[wymanthescienceman]

OK, the main reason I started this thread was that I have yet to get a vacuum take off and 2 RBF's for my distillation rig. I have a water cooled Liebig that has a distillation head on it, its a one piece thing, but I wanted to know if this would work before I spend $75 on the 3 more parts. If anyone thinks that this has a snowball's chance in hell of working, then let me know so I can snap up a vacuum take-off, a 1000ml RBF, and a 500ml RBF.

Another thing is I KNOW that it's NOT necessarily safe to distill HNO3 indoors without a fume hood, but it's extremely cold outside so I can't distill outdoors. How bad of a risk would I take if I did it indoors? All my equipment will have 24/40 joints and is totally sealed, but would there still be a huge risk of leakage and poisoning if the only outlet to outside was the other end of the vacuum line? That was the only plan I had for now. My thought was the vacuum would remove any fumes and drown them in the vacuum trap, I just can't see fumes escaping the joints when it's under negative pressure.

If it's too risky I'm not going to do it, so just tell me how I stand.

[knowledgehungry]

IMHO it is not too risky to do it indoors if you can quickly exit the area and ventilate it. Maybe if you put the other end of the vacuum line into a bucket of water(I am assuming the end of the vacuum line you are referring too is the exhaust end) it would provide one more layer of safety. It is not a good idea to try this if you live in an apartment.

If pssible use an electric heating source so that if things head south all you have to do is pull the cord and run, allowing things to settle down on their own. I would not recommend you do this indoors using a flame heat source.

[wymanthescienceman]

I understand what you mean, I was thinking of just running the exhaust outside but doing it into a bucket of water will also help, though the water may freeze out there :)

And yes, I'm obviously going to use electric heat, the flask in a bath of water or sand. I'm still trying to figure out why Alexires says to use oil rather than water, it seems as though hot HNO3 + Oil = FIREBALL/EXPLOSION. After reading a few other threads I see that water is the only sane liquid to use, but I figure that I'll use sand instead since it is inert. That way I won't have anything but hot acidy sand to worry about in case of implosion, rather than a giant bath of hot dilute acid that will most likely sputter everywhere. The bath I was going to use is a Teflon coated aluminum deepfryer that has variable temperature settings. I figured it would be my best bet since its nice and easy, plus Teflon is always good.

As soon as I get a good deal on some flasks I'll try and get them so I can do a vacuum test with my setup, I really don't want an implosion when distilling ANYTHING. I figure I'll try distilling water under vacuum a couple times first, then if all seems well I'll go for it. I would still like to hear from anyone that can help or has any more tips.

[FUTI]

This is of course sick joke...but why not a glycerine bath? Little crack and you just made two things for the price of one. :P ...only question that remains will it also do the ignition part? You are right NO2 and kerosine combo is used as rocket fuel (and also nitric acid) but I'm not sure will it explode on contact...need to check it.

This raise one OT question for forumities...I know a little about binary CW...but did anyone made reliable binary explosives. I know that black powder is complex mixture but it is intimately mixed prior use. Has anyone made binary explosive of that kind like CWs are made?

I hope that maybe AN based solution as oxidiser and petrol/emulsifier as fuel can make "reliable" mixture. Imagine bomb/shell that mix the components in flight to target - there is a couple technical hurdles in that (I know that) but it is posible to achieve. That would be some kind of safety mechanism/redundant arming sequence. AN based mixtures are very safe already so this isn't best choice for testing the main goal/principle but can be used for developing purposes.

I know also for the Murphy's law : "It is not posible to make device foolproof as fools are so inventive"....so this is maybe overengeenering with little effect...also AN based explosive won't have the same bite like the "old faithfull ones" :).

As for vacuum issue...man if I could distill near 200Celsius boiling liquid (at 760mmHg) with use of a water vacuum pump your NA distilation will go just fine if you don't mess something.

[wymanthescienceman]

I'm just curious, what the hell are you talking about? What does any of what you said have to do with this thread other than the last bit you said? I'm guessing he must have had to be joking about the oil bath to test me or something but what does NO2 and kerosene have to do with anything? And why are you rambling about CW? Honestly, some people around here that talk about making CW are just plain messed up, what kind of crazy person would want to fuck with that other than a terrorist.

For mine and everyone elses sake on this earth, I hope you guys only joke of this CW stuff.

[knowledgehungry]

He wasn't talking about CW he was talking about binary explosives similar to binary CW. As to the glycerine bath, yes he was joking as he says "This is of course a sick joke".

Sand bath is good, however a problem I see with it(same problem with an oil bath) is that even if you pull the plug because you have a leak, the sand/oil is not going to lose its temperature for quite some time.

If there is a large leak it is far too risky to go near the source unless you are wearing a protective suit and face mask as hot HNO3 vapor will oxidize just about anything.

Make sure the room you are doing this in is fuel(most things are a potential fuel, I am referring to solvents etc.) free, make sure there are no nice things made of metal that you don't want to corrode. Make sure you have access to the outside, and a shower if you get it on you.

A homemade "fume hood" is not too hard to create if you only want to vent products to the outside not "scrub" them. Most large hardware store have the things needed, I have one in my basement although my dad made it for drying the basement out rather than for chemical purposes.

[wymanthescienceman]

"As to the glycerine bath, yes he was joking as he says "This is of course a sick joke".

When I was referring to the joke I meant the oil bath that Alexires was referring to. But anyways, using either a water, oil, or sand bath is almost the same when you talk about heat loss. Yes water will lose heat faster than oil or sand but not a whole lot faster to be alot safer. The main reason I want to use sand is that if the flask does indeed implode, it will just absorb the acid and it won't splatter everywhere, but now that I think about it, it will just increase the surface area and all the acid will evaporate really fast causing the room to fill with vapors, which can't be good. Now I'm stuck.

The flasks I was planning on getting are heavy walled RBF's, the same ones this company sells with thier vacuum distillation kit, so I'm guessing that they run a very low risk of collapse, almost none when I consider that my vacuum is nowhere near what a commecial vacuum can pull. The only thing I would have to worry about is my condensor collapsing, which in that case wouldn't be so bad because it wouldn't be dumping a flask full of hot acid everywhere. I think if I test it and it holds up I should be fine, but I was going to use some thick plastic sheeting underneath everything just in case of a spill, that way acid woun't touch antything but the acid resistant plastic. Is this a bad idea? Alot of others use this plastic to make cone funnels for the jar in a jar method like in "HNO3 the easy way".

[nbk2000]

What about using a saturated solution of a mild base, like sodium carbonate, to neutralize the acid in case of a cracked flask?

Yes, there'll be a lot of foaming created by the resulting CO2, but hopefully not enough to cause any greater problem than that created by hot nitric acid splattering everywhere.

You could also hang a large sheet of thick polyethylene sheeting as a tent over the whole assembly so that the acid is contained in case of breakage.

[wymanthescienceman]

I had thought about using a basic solution, but I had thought it would be a bad thing because of the foam but it sounds like it will be alot better to have alot of neutral foam than acid. I think I might try it, depending on how much foam is actually produced. The other thing I had thought was using a base mixed in with sand in a sand bath, but that might not be as good. I'll see when I figure out exactly where I'm going to do this.

The tent idea sounds good, I'll probably try it. But depending on where I do this I'll have to see how much room I have to work with.

[FUTI]

Wow! Sorry man if I insulted you in some way...didn't mean to do that. Joke is a joke. On CW issue...you will notice more that one thread mentioning that subject so better learn to accept it. I had to use that term since I couldn't find any other example to explain idea that sparked reading this thread. Anyway I do appologise to you since that was (as I stated) - OT(off topic).

Anyway sand bath is something I have on my "to do" list. I need to do little book showelling to find a good blueprint for that, and I have seen also some improvisation jobs that use small pearls of zeolites instead of sand. I'm still bumping that idea in my head...like is it safe and ussefull, it is a costly anyway so I wouldn't waste my money if it won't work.

[wymanthescienceman]

No problem with the OT thing, I was just wondering why you decided to put that here, no biggie. And yeah, since there's alot of people that talk about CW, that's fine but I just don't really understand why people talk of such things, and the fact that you put it in my thread kinda put in my head that people might think I was into them, which I'm not.

And as for the sand bath, I was figuring on using regular cleaned silica sand, its cheap and easy to get, 20lb will probably fill my bath and then some. I at first thought it was safer because ther would be no sputtering, but as I already mentioned, it will make the acid evaporate into a death cloud in no time. I'm still mulling the idea of a base in the sand to neutralize the acid, but I don't know how it will work. Another thing I had though of was some kind of container under the bath to catch excess foam in case of worse case scenario. I think I should be fine, I just have to make sure I have no leaks in the system when it's all hooked up. After I get my flasks I'll set up the system and take pics so you all can see what I have planned.