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Author: Subject: Dry Distillation Apparatus
Detonationology
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[*] posted on 11-2-2016 at 16:59
Dry Distillation Apparatus


Imagine a world where glassware is no longer susceptible to cracking due to thermal stress or salt expansion. How wonderful it would be.

Anybody familiar with distilling nitric would agree that cleaning up is a bitch and they have a glassware graveyard to prove it. Dry distillation leads to a similar issue: salts become extremely crusted into the bottom of the flask and do not like to leave peacefully. Distilling DCM from paint stripper is almost as bad. The polymer left in the boiling flask is insoluble in nearly everything and is not easily coaxed with acid!

Many people have described a "paint can still" that can be made from an old metal can and a piece of pipe. It is commonly used to crudely distill solvents (DCM) directly out of the can and also to dry distill salts (benzene synth). With a construction made of metal, it is very resilient to thermal stress and salt expansion issues found with glass. Copper is a very common, relatively inexpensive and chemically resistant metal and would definitely be a step up to the standard steel paint can.

Copper stills have been used for hundreds of years by alchemists and Appalachian hillbillies alike. A design made of copper would be satisfactory for distilling solvents like DCM. Dry distilling NaOH with sodium benzoate in copper may not be as satisfactory if the lye begins to eat through the copper.

...And I don't really need to say what happen when nitric acid meets copper.

So the main question is:

What material and apparatus design is capable of withstanding thermal stress, salt expansion, and HNO3?

[Edited on 2-12-2016 by Detonationology]




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JJay
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[*] posted on 11-2-2016 at 17:30


I typically use a steel can with a copper tube leading to a glass condenser for dry distillation, throwing the can away after a few runs.

Quartz can withstand thermal stress and HNO3, but I'm not sure about salt expansion. You could put the materials in a sacrificial crucible inside the still to protect the apparatus. Certain noble metals like gold and platinum would work but are awfully expensive. Lead is used for sulfuric acid stills, but I don't think it resists HNO3 strongly enough. Stainless steel would probably work.
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byko3y
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[*] posted on 11-2-2016 at 19:56


I agree that sodium sulfate-bisulfate is a pain in the ass do deal with. I've got 2 flasks and one beaker broken because of those compounds. Although I don't fully understand the reason, because sodium sulfate has hardness of 1.5-2.5 by mohs scale, which is close to gypsum. Most likely the reason is high adhesion of sulfate to glass. Calcium sulfate might have a lower adhersion. Or maybe aluminium, or magnesium.
Treatment of hot sodium sulfate with conc. sulfuric acid under reflux conditions might be another way. But those are just ideas, don't treat them like a rule.
Sodium sulfate-bisulfate have high density, so it tends to stick to bottom.
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Detonationology
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[*] posted on 12-2-2016 at 02:29


The problem with calcium sulfate is that it is nearly insoluble in water :o I was planning to buy some calcium propionate to hydrolyze it to propionic acid, but I realized that it was going to be even more of a pain to clean than bisulfate! It would certainly be worth it in the long run to have a special still to use just for these applications.

On eBay, 500mL of propionic acid sells for $65.95, which is absurd. I have calculated that I could hypothetically produce 1000mL of propionic acid for ~$25, using calcium propionate @ ~$7.50/lb and Rooto Drain @ ~$8.50/L. Too bad I would basically be making a flask full of plaster of paris on one side! :(




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[*] posted on 12-2-2016 at 02:55


Wait, what's the problem with nitric acid cleanup? I've done it many times and I've always just dissolved the sodium sulfate in water. Takes a little while, but is completely painless.

Also with DCM what I did is cut a hole in the top of the plastic lid of the metal can and wedge in my distillation head. Then I ran the distillation as per normal, no cleanup required. Just be sure to pour out about 1/2 the DCM mix first, as the stuff foams considerably.
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[*] posted on 12-2-2016 at 05:32


Some stainless steel alloys can stand up to 65% nitric acid, look at the guide below for details.

http://www.bssa.org.uk/topics.php?article=31
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[*] posted on 12-2-2016 at 07:05


I agree with Oscillator, I've had no problems with nitric distillation. Just dissolve the residue in water, no chipping away necessary. Also I successfully cleaned the gunk from distilling DCM from paint stripper with minimum effort by washing with kerosene to dissolve the polymer, then acetone to wash away residual kerosene.

Not to derail the thread or anything, just wanted to point those things out. A more sturdy setup is a good idea for destructive or dry distillation. It's tough to beat the general resistance of glass, though, so I imagine you'd need several pots to handle different situations. Teflon coated vessels are an option, as long as temperature doesn't get too high.
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Detonationology
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[*] posted on 12-2-2016 at 07:22


I've learned that Teflon is not very resistant to hot lye... all that was left of my stir bar was a little black bead spinning in the bottom. I'm quite surprised that more people have not experienced issues with cleaning up after distilling nitric acid; maybe I'm just too impatient, especially when I start chunking up the salt with a glass rod.



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[*] posted on 12-2-2016 at 09:10


Quote: Originally posted by Detonationology  
I'm quite surprised that more people have not experienced issues with cleaning up after distilling nitric acid; maybe I'm just too impatient, especially when I start chunking up the salt with a glass rod.


I found that the RBF, distillation adapter, and/or condenser can be unplugged painlessly by leaving the glassware overnight in a sink filled with hot water.





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[*] posted on 12-2-2016 at 09:13


Quote:
I'm just too impatient, especially when I start chunking up the salt with a glass rod.

Yes you are ─ but I've come close to chunking it up a few times, too!

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[*] posted on 12-2-2016 at 11:52


I was just looking at a compatibility chart for copper and it said that use with DCM was "not recommended." Has anyone experienced any trouble at all distilling DCM with copper?



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[*] posted on 12-2-2016 at 15:27


Yeah. Seems like I recall supplying a chem experiment where the student were to fractionally distill a chlorinated hydrocarbon through a column packed with stainless steel, scrungey material. Might have been Carbon Tetrachloride.

Well, our local hardware store, could only supply about 1/2 the required stainless steel scrubbers. We tried to substitute some of them, with copper plated (steel?) scrungey instead. It wasn't my call. And, it didn't work out.

This copper coated material reacted immediatly with the hot vapors, and corroded. It was a nasty mess.

So, if you are contemplating copper, with any hot halogenated hydrocarbon....be cautious. Good chance there will be problems.

Stainless....maybe OK. Copper, Steel, Aluminum......No!



[Edited on 12-2-2016 by zed]
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[*] posted on 13-2-2016 at 11:37


Detonationology, have you ever seen a calcium sulfate? On my opinion it is one of the most pleasant compound to clean the flask from. Precisely because it is water insoluble.
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[*] posted on 13-2-2016 at 11:59


Quote: Originally posted by byko3y  
Detonationology, have you ever seen a calcium sulfate? On my opinion it is one of the most pleasant compound to clean the flask from. Precisely because it is water insoluble.

No, I have never worked with calcium sulfate, but I was under the impression that it would become a rock solid cake nearly incapable of removing. Considering that water is used to set up plaster of paris, I could not imagine removing it from a round bottom glass, and a 24/40 glass joint. How did you remove a solid cake of calcium sulfate from such a flask with no problems?




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[*] posted on 14-2-2016 at 04:07


Quote: Originally posted by byko3y  
Detonationology, have you ever seen a calcium sulfate? On my opinion it is one of the most pleasant compound to clean the flask from. Precisely because it is water insoluble.


Attention, it is NOT water insoluble. I is slightly water soluble and as you know it's also called plaster of Paris for a reason.

I could tell you of MANY placed where quarries of gypsum in Paris caused problems far after they had been abandoned. They were mostly located Under Montmartre which before they built upon it was just a hill with two main entrances that looked to the Parisians like the entrance to hell (gypsum has to be cooked to make plaster, and if you balance an equation you'll notice plenty of CO2 was released). So every morning, they took out the bodies of homeless people who wanted to heat themselves for free but suffocated.
Basically, a gypsum bank can be as high as 18 meters. You could imagine what would happen if slowly over the course of decades the quarry filled with water, the gypsum dissolved and the buldings atop well... didnt fare well.
Most of the work around Montmartre was done in the 1980 to consolidate the land but accidents still happen.
They still happen especially because civil engineers are a bit short sighted and inject.... concrete!
So now you have gypsum, water, concrete that doesnt let go water through and is slightly acidic.
Brilliant :mad:

For those interested in religion and history, one of such holes Under the northern bank of Paris witnessed a reunion a long time ago between one Ignace De Loyola and his friends. There, they decided to create an order that still survives today: The Jesuites.

[Edited on 14-2-2016 by Herr Haber]

[Edited on 14-2-2016 by Herr Haber]
Cant seem to find out what's wrong with the display of the post. Eww

[Edited on 14-2-2016 by Herr Haber]
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[*] posted on 14-2-2016 at 04:13


Quote: Originally posted by Magpie  

I found that the RBF, distillation adapter, and/or condenser can be unplugged painlessly by leaving the glassware overnight in a sink filled with hot water.


That'll work but you'll still have to move around your RBF unless the concentration becomes to high and the salt doesnt dissolve anymore.
Last time I thought I should put one of my smallest water pumps with tubing going into the RBF to get the water moving.

Last question... Calcium sulfate is... gypsum right? So how about a little bit of hot HCL in your water bath to make things go faster?

[Edited on 14-2-2016 by Herr Haber]

Edit: Fixed broken quote

[Edited on 2-14-2016 by zts16]
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[*] posted on 14-2-2016 at 10:45


I agree Herr Haber that the salt must be washed out with hot water. The soaking overnight just loosens it up in tight spots like the distillation adapter and condenser. By being careful as shown in Doug's Lab YouTube video you will not have saltcake in those tight spots.

Actually I don't bother making nitric anymore as it is reasonably priced though Duda Diesel. I understand this is not a practical approach for those living outside the US.

In the years ahead I can see it being more difficult to buy nitric acid. But it will likewise eventually be difficult to buy nitrate salts too. Then we will be forced to develop Birkland-Eyde technology.




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Detonationology
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[*] posted on 14-2-2016 at 13:52


Buying nitric acid from Duda is only cost efficient if you purchase 10L or more at a time @ $22.80/L. Otherwise, it is $90 for 950mL. I buy KNO3 prills from Duda, which I powder in a blender, with the sole purpose to make nitric. 10lb of KNO3 makes ~2L of nitric @ $20/L using Rooto drain. For me, 2L is a very secure and satisfying amount to have on hand. 10L is MUCH more than I would want to have on hand at any given time.



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[*] posted on 14-2-2016 at 14:58


Yes, it looks like Duda is getting greedy or doesn't like small orders.

Actually, my purchased bottle of 70% nitric acid, 500 mL, is from Elemental Scientific. I see they now have 64% nitric, 500 mL, for $17.

[Edited on 15-2-2016 by Magpie]




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