Detonationology
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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]
“There are no differences but differences of degree between different degrees of difference and no difference.” ― William James
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JJay
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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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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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The problem with calcium sulfate is that it is nearly insoluble in water  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! 
“There are no differences but differences of degree between different degrees of difference and no difference.” ― William James
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Oscilllator
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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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Dr.Bob
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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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MrHomeScientist
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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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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.
“There are no differences but differences of degree between different degrees of difference and no difference.” ― William James
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Magpie
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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.
The single most important condition for a successful synthesis is good mixing - Nicodem
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hissingnoise
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| 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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Detonationology
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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?
“There are no differences but differences of degree between different degrees of difference and no difference.” ― William James
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zed
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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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byko3y
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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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Detonationology
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| 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?
“There are no differences but differences of degree between different degrees of difference and no difference.” ― William James
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Herr Haber
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| 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 
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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Herr Haber
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| 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.
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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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Magpie
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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.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Detonationology
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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.
“There are no differences but differences of degree between different degrees of difference and no difference.” ― William James
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Magpie
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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]
The single most important condition for a successful synthesis is good mixing - Nicodem
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