Sciencemadness Discussion Board

Distillation: retort vs. flask + condenser

Gearhead_Shem_Tov - 1-10-2008 at 19:46

I'm just getting into amateur chemistry. On my short list of projects to do is making silver nitrate. I would like to make the nitric acid first since I have sulfuric acid and potassium nitrate already to hand.

My question is this: which distillation setup would be preferable for acid production, a dedicated retort or a lashup of a RB flask and a separate condenser? What are the advantages of one over the other?

I don't own any tapered ground glass equipment, just a few ordinary borosilicate flasks, so I would need to do something with a teflon-wrapped rubber stopper if I went with a separate condenser.

Thanks!

-Bobby

not_important - 1-10-2008 at 20:20

A retort, or an all glass still, is better for something like nitric - both corrosive acid and an oxidiser.

If by "Teflon wrapped" you mean the white plumbing Teflon tape , you might not be happy. That tape is fairly porous, it's meant to be compacted in the threads of plumbing joints. The yellow or red tapes, approved for gas line use, are better.

An old method for dealing with such distillations was to soak cork stoppers in waterglass, or paint them with waterglass after sticking the glass parts through their homes and before inserting into the flask opening. But glass joints, with Teflon sleeves or using thick phosphoric (sometimes mixed with bentonite) on the joints, are the best way to go.

Gearhead_Shem_Tov - 1-10-2008 at 20:35

Quote:
Originally posted by not_important
A retort, or an all glass still, is better for something like nitric - both corrosive acid and an oxidiser.

If by "Teflon wrapped" you mean the white plumbing Teflon tape , you might not be happy. That tape is fairly porous, it's meant to be compacted in the threads of plumbing joints. The yellow or red tapes, approved for gas line use, are better.


OK, nice to know. Is there any special technique for doing the wrapping? I've read about doing this, but I've never actually seen it. I have a hard time visualising how to completely cover the flat end of a stopper.
Quote:
An old method for dealing with such distillations was to soak cork stoppers in waterglass, or paint them with waterglass after sticking the glass parts through their homes and before inserting into the flask opening.


Neat! I have several old amateur chemistry books, but I don't recall seeing that technique listed.
Quote:
But glass joints, with Teflon sleeves or using thick phosphoric (sometimes mixed with bentonite) on the joints, are the best way to go.


Understood. I'm still in the very beginning of this, so I'm trying to put off the more expensive purchases until I've learned a bit more.

I'm leaning toward getting a simple retort because, just looking at it, it seems as if there would be less to go wrong -- fewer pieces, fewer joints, and all glass.

The down side, as far as I can see, is a retort might be less versatile (but I may simply be showing my ignorance, here).

-Bobby

Picric-A - 2-10-2008 at 08:54

If i were you i would use a all glass retort. They are quite cheap and as long as they are cleaed of any nasty organic residues they have exellent chemical resistance.
Simply lead the neck of the retort into a ice cooled flask and you will be fine. Retorts are cosiderably cheaper than quickfit and i wouldnt risk using anything other than those two.

I just wanted to ask, does anybody know what material the big industries use when making conc nitric? do they use teflon coated steel or something? thanks,

[Edited on 2-10-2008 by Picric-A]

gsd - 2-10-2008 at 09:23

Quote:
Originally posted by Picric-A

I just wanted to ask, does anybody know what material the big industries use when making conc nitric? do they use teflon coated steel or something? thanks,

[Edited on 2-10-2008 by Picric-A]


Industrially Nitric Acid is concentrated in process plant made of Glass

Have a look at this link:http://www.qvf.com/en/processsystems_3/mineral%20acids/ConcentrationingofNitricAcid.shtml

gsd

Picric-A - 2-10-2008 at 11:52

cool thanks for that link gsd, i throught for some reason glass would be too expencive for the huge colms they have.

gsd - 2-10-2008 at 14:45

Industrial glass is an expensive Material of Construction (MOC). But the alternatives to it like Tantalum metal are even more costly.

Borosilicate glass is a very important and very widely used MOC in chemical process industry. For processes like Halogenation it is indispensible.

There are several established glass process plant manufacturers like Schott-Duran (Germany), QVF (UK), Borosil (US) etc who manufacture huge tailor made plants.

gsd

Magpie - 2-10-2008 at 15:17

This not meant as disagreement with gsd, but Shreeve in Chemical Process Industries, 2nd Ed (1956), says on pp 416-17 that the absorption tower for 65% acid can be made of stainless steel. For the 95-99% acid, high-silicon iron.

Gearhead_Shem_Tov - 2-10-2008 at 15:43

Quote:
Originally posted by Magpie
... Shreeve in Chemical Process Industries, 2nd Ed (1956), says on pp 416-17 that the absorption tower for 65% acid can be made of stainless steel. For the 95-99% acid, high-silicon iron.


High-silicon iron ... hmm ... would transformer lamination iron have high enough silicon content? Not that I have any application; it's just nice to know the possibilities.

-Bobby

Gearhead_Shem_Tov - 2-10-2008 at 16:05

Quote:
Originally posted by Gearhead_Shem_Tov
High-silicon iron ... hmm ... would transformer lamination iron have high enough silicon content? Not that I have any application; it's just nice to know the possibilities.


Turns out transformer laminations only have between 1-3% Si; the high-Si stuff has 14.5% Si and 1% carbon. It's very brittle, much like cast iron, and will handle sulfuric acid in all concentrations up to--and including--its BP. It can handle nitric acid above 30% to its BP; below 30% it goes up to 27C. (Figures quoted from Schweitzer, Encyclopedia of Corrosion Technology, p. 290, accessed via Googlebooks.)

-Bobby

not_important - 2-10-2008 at 16:24

A retort is less versatile , but as already said quite simple. A moderately long necked flask to use as a receiver and a tub or pan to put under the flask and hold cooling water or ice does well for many inorganic and some organic distillations. And it avoids the problems of joints.

If the distillation gives off much non-condensible gas you ether need good ventilation, a fume closet or work outdoors, or a standard distilling setup that can be arranged to draw off the gas(es) and capture, destroy, or ventilate them.

Anything requiring much precision in temperature control, as many organic distillations do, really wants a standard distilling setup. For solvent cleanup and recovery, including that needed for some inorganic (ppt ammonia complexes of copper or cobalt), a low cost simple distilling flask and condenser will do. It need not be ground joints, rubber, silicon, or cork stoppers will do for many solvents. I'd suggest that sort of low end system as your second distilling purchase, given that a retort fits your first needs.

Trying to wrap stoppers in Teflon tape for protection is somewhat a waste if time IMHO. You can run tape from along the side over the bottom and down the opposite side, then wrap the sides with more tape. But it's a kludge, likely to leak both to the stopper and out into the surrounds.

Gearhead_Shem_Tov - 2-10-2008 at 19:17

Quote:
Originally posted by not_important
A retort is less versatile , but as already said quite simple.
...
If the distillation gives off much non-condensible gas you ether need good ventilation, a fume closet or work outdoors, or a standard distilling setup that can be arranged to draw off the gas(es) and capture, destroy, or ventilate them.


This was my intuition.
Quote:
Anything requiring much precision in temperature control, as many organic distillations do, really wants a standard distilling setup. For solvent cleanup and recovery, including that needed for some inorganic (ppt ammonia complexes of copper or cobalt), a low cost simple distilling flask and condenser will do. It need not be ground joints, rubber, silicon, or cork stoppers will do for many solvents. I'd suggest that sort of low end system as your second distilling purchase, given that a retort fits your first needs.


Thanks, that's very helpful. One thing regular condensers have going from them is I can order them inexpensively here in Australia (so far the only source for retorts I've found have been in the USA, so I have to pay for the shipping).
Quote:
Trying to wrap stoppers in Teflon tape for protection is somewhat a waste if time IMHO. You can run tape from along the side over the bottom and down the opposite side, then wrap the sides with more tape. But it's a kludge, likely to leak both to the stopper and out into the surrounds.


That's what I figured. I suppose sodium silicate and corks might work better in terms of the seal.

For the receiver in a retort setup, though, you don't want an air-tight seal, right? The condensate has to be able to displace air from the receiver at atmospheric pressure, so that's why I would need to use a fume hood or work outdoors.

-Bobby

not_important - 2-10-2008 at 20:19

Right, you don't need any stopper for the report/receiver flask connect.. The retort neck was sometimes wrapped in asbestos in a small band, more as a cushion to avoid glass-glass bashing and to keep dust out of the receiver than as a seal proper.

What gases are formed in your distillation will determine ventilation issues, NO2 is nasty so some sort of venting is wanted. You might make a mini-hood using a lightweight framework and heavy plastic sheeting, able to be mostly closed up to keep fan requirement down, and rig the exhaust so it first is pulled through loose damp Na2CO3 to scavenge the acidic gases before they get to the fan. If you're really energetic you could make a small scrubber using Na2O3 solution and plastic mesh to increase contact area, but that may be a bit much.

A possible cheaper alternative is a simple distilling flask with both a long side arm and a long neck above the sidearm. Insert the side arm quite a ways into the stopper at the condenser, so that gases coming out of the side arm get cooled and condensed quickly enough that little drifts back up to the stopper. Similarly the long neck above the side arm allows the distillate to condense before it reaches the stopper there. You could even wrap a few turns of plastic tubing carrying cooling water around the neck just below the stopper. If you use a thermometer you'll have to insert it extra far into the stopper, which will throw its reading off a little but likely not enough to matter for your applications.

Retort recommendation?

Gearhead_Shem_Tov - 3-10-2008 at 18:10

Does anyone know anything about Scientific Equipment of Houston on ebay? I'm considering this 1000ml retort:

[url=]http://tinyurl.com/3sja3q[/url]

They discourage international buyers -- and you don't get much more international than Australia -- from ordering fragile items, which a glass retort obviously is. Anyone familiar with their products and/or have experience with shipping glassware internationally?

-Bobby

grndpndr - 13-10-2008 at 04:41

Ive bee looking at the glass retorts as less expensive means of distlling nitric acid however retorts ive seen have very short necks typically 250ml retort may have 10 in necks same with the 500ml the 1000ml may have 14in necks.Is that enough with the reciever in a ice bath to hopefuy condense the nitric acid.Price differentials seem quite low being all glass sysems w/graham condensers 1000-2000l flat boton boiling flasks as well as acid resitant teflon thermometer adapters with therometers at $99-$105 but the reciever is the purchasers responsibility as is the support for the distilation rig a small problem with anyone with any handyman skills at all And is needed with a reort in any event!With the price of a 500-1000 glass retort w/o thermometer adapter or receptor is $60 and up when another $40 an a small amt of ingenuity results in a more capable condenser.Im Quite $ conscous but the $40 dfference seems just to little savings for
whats gained.Ill save an exra month if need be and of course longer condensers are available at very small cost as are the needed stands.Some $160 for complete 2000Ml
flat bottom boiing flask wth therometer takeof and graham condenser with commercial stands and reciever at $160 The low buck $99-$105 borosilicate components will serve just as ably with a very small amt of work.Change my mind! i intend to only use it to distill nitric acid are the retorts with ther short necks capable of condensing nitric from SA and a nitrate in a ice bath reciever?

These companys all seem to be the same adverising on E-
bay with decent rpresenations of thier products wit direct links to thr stores as well as the chance of bidding less than advertised price.

Finall would it be practical to substitute the glass stopper of the retort for a thermometer adapter of teflon?

[Edited on 13-10-2008 by grndpndr]

[Edited on 13-10-2008 by grndpndr]

kalacrow - 19-10-2008 at 20:15

Hm. For those prices, I'd just buy the real stuff.

http://unitedglasstech.com

grndpndr - 29-10-2008 at 00:33

I try to buy the best glass commensurate w/safety sake-budget.Even if it may lead to less capability such as a retort/collector modified w/thermometer using waterglass cork/teflon replaced after every run so long as the retort is of sufficient quality and sand bath/ice bath capable of absorbing the results of broken retort/ondenser avoiding the corrosive cascade of Hot acids.Safety is of course #1 priority.Besides a painful wound should one be 'lucky'.Explaing the severe chemical burn could be difficult to hospital staff/police.

At the time my needs are not at all sophisticated still its best to buy as best as can be afforded.Appreciate all the info particulary the waterglass idea! More research from appliations to specifications/sources.Great stuff, thanks all!

[Edited on 29-10-2008 by grndpndr]