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Eclectic
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I found a old patent or reference in Muspratt or the like from late 1800's where they used pumice stone for added area too. This in a cast iron
reactor.
Do you know if CPVC is resistant to liquid SO2? The pressures seem fairly low and you could overcoat it with fiberglass.
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garage chemist
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I filled a test quantity of SO2 (around 50g) into my oxygen cylinder, which has a nickel (?) plated brass valve, with the inner moving parts made of
bare brass. It seems to hold up very fine so far. After I've used up the SO2, I will open the cylinder again and disassemble and inspect the valve.
Then I can prepare for filling the cylinder to its full capacity.
I found some bits of possibly useful information in some old chemistry books. In "Elements of chemistry" by Sir Robert Kane:
http://books.google.de/books?id=IYEEAAAAQAAJ&pg=PA1020&a...
a method for production of SO2 is given, consisting of heating a mixture of MnO2 with sulfur:
MnO2 + 2 S ---> MnS + SO2
This could be useful for those wishing to use only elemental sulfur as the sulfur source.
Also, for preparation of SO2 on a larger scale, heating charcoal with H2SO4 is recommended, giving a gas mixture of 2 parts SO2 with 1 part CO2, but I
see no reason to do this when sulfur with a little Fe2O3 can be used instead of charcoal.
I order to prepare 1kg of liquid SO2, I realized that I have to liquefy it in portions as my cryostat is too small to accomodate a 1L round-bottom
flask. Thus, there is a need for intermediate storage of the liquid SO2. Although possible, I would rather not place glass flasks of liquid SO2 next
to the frozen food in our freezer.
I have a 2L glass dewar vessel into which I could pour the liquid SO2 to pool the portions. It would obviously have to be located outside while being
filled. What worries me is the possible ingress of atmospheric moisture, which would promote corrosion of the steel and brass. Do you think that a
styrofoam cover (if it isn't softened by SO2 like PET) provides enough protection against that?
The dewar vessel is cylindrical with a wide mouth, with no lid.
Better ideas for intermediate storage of SO2?
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watson.fawkes
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Quote: Originally posted by garage chemist  | | I order to prepare 1kg of liquid SO2, I realized that I have to liquefy it in portions as my cryostat is too small to accomodate a 1L round-bottom
flask. [...] Better ideas for intermediate storage of SO2? |
You're farther ahead than I am in working on this
project, although I did just acquire a lecture bottle for the purpose. My solution, which I'm in the middle of acquiring gear for, is to liquefy with
a refrigeration compressor. SO2 is refrigerant R-764 and was commonly used before the freons. One of the advantages of this approach is that you
evacuate the storage bottle before filling, and then you're generating and pumping with a fully sealed system, so assuming your drying train is
working right, you get good-and-dry SO2.
Apropos of the question you posed, the compression stage isn't a batch process, so there's no need for intermediate storage. The main disadvantage of
this method is that the generation stage needs to have a fairly small waste gas volume, or else there's more work to be done to deal with that.
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garage chemist
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I would probably do it that way too, if I could cheaply obtain expendable old fridge compressors. But I can't.
All old fridges are brought to the scrapyard and get recycled by special companies that also dispose of the CFC refrigerant in an environmentally
friendly way.
The scrapyard doesn't let anyone near the old fridges, and asking doesn't help.
The refrigeration compressors are also quickly destroyed by pumping corrosive gases like ammonia and SO2. The compressors of the old-time SO2
refrigerators were built completely different (openly accessible motor and shaft).
Also, air in the system is a big problem as it collects in the gas cylinder, raising the pressure required for liquefaction.
One can evacuate the cylinder beforehand and purge the compressor with the gas to be liquefied, but during the unavoidable refilling of the gas
generator, air will get into the system again.
Air in the system is not a problem with pressureless liquefaction by cooling. Here, ingress of moisture is the issue, along with the question of
intermediate storage of the cold liquid. A freezer dedicated for lab use would solve the second problem.
The ultimate gadget for filling gas cylinders at home would be the "Universal oil-free laboratory compressor for corrosive gases". Motor openly
accessible, pistons sealed with PTFE, all exposed parts made of steel, capable of compressing chlorine.
Perhaps someone who is really good at machine-building may one day construct something like this.
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Fleaker
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This is an interesting thread. It's also scary. Liquid sulfur dioxide is not something I'd ever with to have a spill of without being far away!
garage_chemist, on my 70 kg tank, it has a siphon tube and the liquid expands in the stainless tubing once outside of the bottle.
Bulk LSO2 is about $1.05/kg so making it for 10X that price on the small scale certainly isn't bad.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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Natures Natrium
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Wow, I am so jealous of your cryostat. I can think of dozens of fascinating uses just off-hand.
As for SO2 in an old, small, stainless steel lecture bottle (previously used for oxygen) with a brass valve, I can report that my bottle is still
holding up to this day. That is around 5 years, I believe. The gas was mostly dried by the precipitation of ice crystals as I recall (since I was
using dry ice/acetone, temp near -60C).
Your method of generating SO2 sounds so much more convenient and controllable than HCl on metabisulfite, particularly since you seem to have found a
suitable catalyst.
Good stuff, I just had to come out of lurkdom and drop my two pennies. :-)
\"The man who does not read good books has no advantage over the man who cannot read them.\" - Mark Twain (1835-1910)
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tetrahedron
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MnO2 + 2S ---> MnS + SO2
those old sources gladly understate the dangers involved in the experiments..how vigorous is this reaction? up to what scale is it a safe prep? i have
a feeling you tested it yourself..do you have any detailed data on apparatus, yield, etc?
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unionised
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Re the original posting and title (and I realise it's a bit late)
http://www.tandfonline.com/doi/abs/10.1080/00028896709342519
SO2 leaks through (at least some) plastics
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garage chemist
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| Quote: Originally posted by tetrahedron |
those old sources gladly understate the dangers involved in the experiments..how vigorous is this reaction? up to what scale is it a safe prep? i have
a feeling you tested it yourself..do you have any detailed data on apparatus, yield, etc? |
No, I haven't tested it. Try it out yourself and report your findings. The original text recommends to heat this mixture in glass flasks, so it
definately isn't a pyrotechnic mixture.
Personally I would trust these old texts any day in contrast to the bullshit that can be seen on some youtube videos and wikipedia articles. If
there's one thing that these old-time chemists were really good at, it's experimental technique.
I have switched to burning sulfur in a stream of pure oxygen in my quartz reaction tube. This is far less dangerous than the method using boiling
concentrated H2SO4 and sulfur and produces a much faster stream of SO2, saving lab time.
It also fills my garage with the most beautiful and brilliant blue light from the flame.
The only problem with this process is that the intense heat of the sulfur-oxygen flame vaporizes a part of the unreacted sulfur, which condenses into
a fine sulfur aerosol upon cooling in the downstream section of the tube. So much of this aerosol is produced that a glass wool filter is very rapidly
clogged, producing so much backpressure that the joints of the quartz tube pop open despite clamping them.
If no gas filter is employed, then the aerosol deposits on the glass coil of the condenser that is being used to liquefy the SO2, fouling up the heat
transfer and necessitating labor-intensive cleaning of the condenser after each production run.
Additionally, the sulfur aerosol is also suspended in the liquid SO2, necessitating a redistillation of the crude liquid to obtain a clear SO2
product.
I need to develop a gas filter that can hold a large amount of solids before becoming saturated.
Adding to the problem, the sulfur aerosol deposits as a rubbery, sticky layer of "plastic" sulfur, not as a dust. This is what blocks the glass wool
filter so quickly.
On the bright side, this process gives an excellent yield.
I repeatably obtain an 85% yield of liquid SO2 after the redistillation.
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tetrahedron
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thanks for the input. i might. | Quote: | | the aerosol deposits on the glass coil of the condenser that is being used to liquefy the SO2 |
have you tried a room-temperature precondenser? also, do you have a lot of unreacted oxygen?
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garage chemist
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There is almost no unreacted oxygen, that's the beauty of the process and the reason for the high yield upon direct liquefaction of the burner offgas.
The reaction is arranged so that the hot flame contacts (and vaporizes) plenty of excess sulfur, consuming all oxygen. If I had excess oxygen in the
offgas then I wouldn't have the aerosol problem, because the aerosol would burn up.
But since oxygen is the more valuable precursor (I'm using a high pressure cylinder) I choose to work under conditions of excess sulfur. Also, without
excess sulfur, I would face the problem of significant co-production of SO3, which would require special purification of the crude SO2 to remove it.
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Yamato71
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I have used epoxy coated aluminum paintball CO2 cylinders to store gases and liquified gases up to 1800 psi without leakage. The black 1/2 to 1 liter
bottles have an "O" ring where the cylinder valve seals into the aluminum body so that you can condense liquified gases such as SO2, NH3, etc directly
into a chilled bottle and then screw the valve back on before allowing the bottle to warm up to RT. This is especially effective for the collection
and storage of anhydrous ammonia using an ammonia generator and a dry ice/acetone "cold finger" condenser. I have an assortment of these bottles
charged with Ar, N2O, H2, O2, N2, CO, CO2, NH3, H2S, etc for lab use similar to the "lecture bottle" sized cylinders we remember from college.
Standard CGA gas pressure regulators can be fitted to to the paintball cylinder valves, usually with a 1/8" NPT nipple for low pressure gas delivery.
[Edited on 5-12-2012 by Yamato71]
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garage chemist
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Are the valves of the paintball cylinders made of steel? They would be perfect for ammonia if they were.
The valves of the 1L medical oxygen cylinders that I'm using are nickel plated brass. They hold up perfectly with sulfur dioxide, but aren't suitable
for ammonia.
I don't have a cheap source for dry ice. I'm using my selfmade compressor cooler for condensing gases.
Well done on condensing and bottling all those different gases!
My SO2 cylinder now contains about 700g and that should be enough for my planned experiments. I always chilled the bottle in my -30°C methanol bath,
unscrewed the valve and poured in the prepared batch of redistilled liquid SO2.
That way I have accumulated this amount of SO2, preparing batches of about 200g and collecting them in my cylinder.
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Yamato71
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Actually, most of the valves I've seen on paintball cylinders are brass, which rules out their use for moist ammonia. I have also seen stainless
steel valves. As to using brass valves for ammonia, if your NH3 is anhydrous, you shouldn't have any problems.
In my case, I generated NH3(g) using an ammonium salt (nitrate or chloride) and NaOH. The moist NH3 was then passed through a column of sodium amide
(NaNH2), which converted any residual water into more NH3 and NaOH. This pre-dried ammonia gas was then passed to a large insulated RBF containing
sodium metal shot, a stirbar and topped with a large dry ice/acetone reflux condenser vented with a CaCl2 drying tube. As the NH3 condensed into the
RBF, the sodium dissolved into the liquid ammonia and destroyed any residual traces of water. As long as the solution was dark blue, the ammonia was
sufficiently anhydrous.
When the flask held enough anhydrous ammonia, the open paintball cylinder was screwed to a homemade adapter that threaded into the cylinder and mated
with the taper on the end of the condenser. The paintball cylinder was then lowered into a dry ice/acetone freezing mixture and a vent tube carried
NH3(g) from the RBF to the condenser atop the cylinder. As the anhydrous NH3/Na mixture warmed up, the gaseous ammonia was again condensed into the
aluminum cylinder.
This step was essentially a final distillation as the metallic sodium was left behind in the flask, together with a bit of NaOH from the dehydration.
When the anhydrous liquid ammonia finished distilling into the paintball cylinder, the valve was screwed into place and the cylinder was removed from
the freezing mixture.
One of these ammonia cylinders with a brass valve sat on the shelf more than 3 years before it was used. After it was emptied, the valve was removed
and inspected closely. Even after three years, the brass was still bright and shiny without a trace of corrosion. As long as the ammonia is strictly
anhydrous, having brass fittings shouldn't be an issue.
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garage chemist
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Yes, drying liquid ammonia with sodium is what Brauer recommends too. Since I don't have any sodium amide, I predried the gas with KOH flakes.
How do you unscrew the valve from the paintball cylinder?
With my medical oxygen cylinders this was always a big problem, requiring excessive use of force. I still have two cylinders on which I haven't been
able to unscrew the valve at all.
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watson.fawkes
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| Quote: Originally posted by garage chemist | | With my medical oxygen cylinders this was always a big problem, requiring excessive use of force. I still have two cylinders on which I haven't been
able to unscrew the valve at all. |
If you've got a friend with a chain vise, of the kind used by
pipefitters, they'll clamp a cylinder well enough to change the valve. Use a brass shim around the cylinder if you don't want to mar it. Also, use a
large wrench with a long handle.
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garage chemist
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Can you link me to a picture of the device that you're writing about? Never seen anything like this, and google turns up nothing that seems right for
the job.
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Yamato71
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Since the valve on the paintball CO2 cylinder is sealed with an "O" ring, it can be unscrewed by using a simple 1" open-end wrench (spanner for our EU
friends) and resealed the same way with only moderate hand torque. GC, what device are you asking to see, the paintball cylinder or the chain vise?
BTW, a strap wrench will work to secure the cylinder as well. Normally, I just wrap an old towel around the cylinder and clamp it into a bench vise.
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garage chemist
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I'm asking to see the chain vise. Though I am also unsure about which paintball cylinder Yamato means, the CO2 kind or the nitrogen kind.
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Yamato71
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I am only familiar with the liquid CO2 variety. They use an O-ring sealed valve so that they can be recharged in the field using dry ice and an open
end wrench. They are powder-coated aluminum, rated to 1800 PSI (12,410 kPa).
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watson.fawkes
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In the USA, RIDGID makes a quality, popular line of pipefitting tools.
Here's their bench-mounted chain vise. You can't see it that well in that product photo, but the pins holding the links of the chain together stick out on each
side of the links. There's a pair of recesses in the vise body, on the left, where the two ends of pins on the chain catch in the body of the vise.
The handle on the right tightens the chain. All but the smallest have a 4" / 100 mm diameter capacity, plenty big enough for lecture bottles or
paintball cylinders.
There are other ways of rigging up a strap or chain around a cylinder to hold it while torquing on the head. This is by far the most direct way.
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Natures Natrium
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Well, crap. I recently tried to use my 6 or 7 year old bottle of SO2, only to find that the valve is completely frozen shut. At some point in the
future, I will chill the bottle and unscrew the valve from the bottle to see what the deal is. I am supposing that the culprit here is inadequate
drying of the SO2 gas before storage.
\"The man who does not read good books has no advantage over the man who cannot read them.\" - Mark Twain (1835-1910)
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Texium
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Thread Moved
20-11-2023 at 12:45 |
Texium
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Thread Moved
20-11-2023 at 12:46 |
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