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microcosmicus
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I'm beginning to lose some of my interest in this hobby,
its seems I cant step left right or centre without fear of a
carcinogen, a precursor, or a poison. In physics the scares
were much fewer and far between.
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As someone else approaching a chemistry hobby from a physics
background, this sounds rather odd to me. I mean, in chemistry,
one is only fiddling around with the outer electrons of atoms at
relatively low energies and conditions not that far removed from
everyday life, not trying to rearrange the constituents of nuclei,
recreate the conditions of the early universe, or deal in realms
where matter can become energy, and the very structure of
spacetime can be tied in knots.
Some physics scares:
Almost any particle beam or radioisotope is a carcinogen.
Potentials in the millions of volts.
Intense RF fields which can fry anyone in the way.
Runaway nuclear chain reactions which can destroy a city and
leave it radioactive for years..
Temperatures so high that the thermal radiation is in the form of x-rays
Compared to this, I consider chemistry a pleasant stroll through the park.
For me, what makes this hobby so attractive is the opportunity to
play with the strange microscopic world of quantum mechanics in a
relatively tame setting. For instance, I can observe a singlet-triplet state
transition in oxygen which gives off a visible photon. By contrast, if I was
looking at an analogous transition in a nucleus, that would involve
an x-ray and its analogue in particle physics would involve a
gamma ray.
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garage chemist
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You would encounter the same type of fume if you just concentrate sulfuric acid by boiling, unless you use a distillation setup (which I always use to
concentrate and denitrate waste nitrating acid and other dilute waste acids from processes where only the hygroscopic property of H2SO4 is needed. The
recycled conc. H2SO4 finds use in washing bottles.).
I think a significant number of members here have at some time made conc. H2SO4 from battery acid.
Such carcinogens are only a big deal if you work with them pretty much every day for years of your life, as in an industrial setup.
If you are going to make some SO3 in your lab for occasional use the risk is negligible.
This stuff has to be made and handled under the fume hood anyway as you will quickly find out the first time you do it.
Although the smoke itself is pretty tame and only very slightly irritating, as chemoleo has pointed out in the old oleum and SO3 thread, you just
don't want to fill your lab with it.
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not_important
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And if you are really worried about SO3 fumes, add a large bottle with some 5% aqueous ammonia in it to the end of the wash train, then vent that
through a long tube through a plain water wash. The large bottle and long tube are to give plenty of opportunity for the SO3 to react with NH3(g) and
H2O(g) to make ammonium sulfate.
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Pixicious
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| Quote: | [Quote]
As someone else approaching a chemistry hobby from a physics
background, this sounds rather odd to me. I mean, in chemistry, ...
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Well said microcosmicus
A few years ago (Has this been achieved yet) they were attempting to make a few black holes in a giant machine..
Back to Chemistry..
[Edited on 9-4-2008 by Pixicious]
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Polverone
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EDIT: After doing some searching, I realize that BromicAcid and S.C. Wack have previously discussed the Wolters magnesium modification described below
in the Oleum and SO3 thread. This may not be as interesting as I thought.
According to George Lunge's works on sulfuric acid (The Manufacture of Sulphuric Acid and Alkali, with the Collateral Branches: A Theoretical and
Practical Treatise, various editions) there is a patented modification that permits lower working temperatures for the pyrosulphate
decomposition. Wolters (given as Walters in some other books), in German patent 3110, March 5, 1878, describes using a 1:1 equivalent mixture of
magnesium and sodium sulphates, converted to acid sulphate and subsequently pyrosulphate, ultimately liberating SO3.
Lunge says "Experiments made in my laboratory with Wolters's process have to a great extent confirmed these statements [given in the patent]." So it
does not appear to belong to the class of misleading and/or irreproducible patents which are so easy to find.
The Principles of Chemistry By Dmitry Ivanovich Mendeleyev, A. J. Greenaway, George Kamensky, Thomas Atkinson Lawson also suggests the use of
the magnesium/sodium salt mixture, though it is unclear whether the authors tested the procedure also or if they are just parroting the patent
literature or Lunge.
Manual of Chemical Technology By Johannes Rudolf Wagner, William Crookes, Ferdinand Fischer makes reference to the mixed salt approach again
and says that the decomposition takes place at 600 degrees Celsius. It is unclear if this is the start of decomposition or the peak temperature for
the process, and it is again unclear if the process description comes from experience or from other literature.
If the working temperature is 600 degrees, or not much higher, it raises the interesting possibility of using much cheaper borosilicate apparatus.
This is far above the suggested working temperature limits of borosilicate, but considerably below its softening point. I would not hesitate to
attempt a 600 degree reaction in borosilicate, though I would not expect to reuse the apparatus. Given the relative cost and availability of
borosilicate vs. vycor or quartz, it may not be a bad trade-off to use borosilicate vessels in a disposable manner. Of course, as len1 has shown,
sometimes the right vinegar dispenser is all you need.
Even if it does not permit the use of cheaper vessels, the mixed magnesium/sodium process may be of interest simply for consuming less power, and
producing less wear on the apparatus, due to lower temperatures.
All the books I've mentioned can be found on Google Books if you wish to read more.
[Edited on 4-18-2008 by Polverone]
PGP Key and corresponding e-mail address
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len1
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I think the NaHSO4 decomposition can be done in borosilicate right now. I have done the pyrosulphate decomposition three times in the box oven -
which has the great advantage over the tube oven of a much more uniform temperature (therefore max T ~ average T) each time the first SO3 appears at
650C peaks at 720C, and the last remnants come over at 780C.
I have deliberately placed some borosilicate glassware not dear to my heart (ie previously chipped or broken - like not _important I throw nothing
away) at various places in the oven. There is no change in its appearance, except for a hint of fogging in some places. So if you dont mind a flask
and a bend possibly freezing and losing their shine, its all go. Its even better than you say - they can be reused for this processes - though
probably better keep them out of other reactions.
MgSO4 is more basic than Na2SO4 so im surprised at its purported effect (50-100 degree lowering of temperature). It might be worth a try as an
experiment - though the hassle of having to make the Mg(HSO4)2 might not be worth the slight lowering in temperature for a preparative technique. Len
[Edited on 19-4-2008 by len1]
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Magpie
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@garage chemist
I have assembled an apparatus for making SO3 from NaHSO4 per your method. This quartz glass assembly has ground glass connectors. The one clip used
is ptfe. The ID of the final tube is 8mm. The tube in the furnace is 400x22x25mm.
Let me know if you have comments or suggestions. Thanks.
[Edited on 9-1-2011 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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garage chemist
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This looks good and should work without problems.
The PTFE clip is probably OK to use, but the temperature of the evolving H2SO4 vapor may be a bit too high for it. If you can replace it by steel wire
it would be more reliable.
Do you plan to leave the joints completely unlubricated (as I have done in the past, but would not recommend) or are there PTFE liners in there? PTFE
can't be used at the connection from retort to extension, it's way too hot.
I like to dust the quartz joints with graphite powder before assembly- this doesn't provide any real lubrication, but has always prevented them from
freezing.
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metalresearcher
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Interesting. I have an electric (Kanthal) furnace which can heat till 1200oC.
Where did you buy the quartz glassware ?
I found this : Click ! but these are brutally expensive such as $30 for a simple test tube !
[Edited on 2011-1-9 by metalresearcher]
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Rosco Bodine
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There was an interesting bit of related topic discussion between 497 and myself
in another thread where the possible use of a basic ferric sulfate was being described. The following post and page describes the Monsel's salt which
may fit the bill as another useful precursor for pyrolytic decomposition yielding SO3.
http://www.sciencemadness.org/talk/viewthread.php?tid=2824&a...
Related discussion began on the page preceding, so there are two pages there about this possible method which may be worth an experiment if anyone is
curious to see if the basic ferric sulfate Monsel salt would actually work as contemplated in hope of producing a higher yield of SO3.
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Magpie
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@garage chemist
My plan was to leave the joints unlubricated. I have no ptfe liners. I do just happen to have acquired some graphite powder, however, so will use
that as you suggest.
@metalresearcher
Quartz glassware can be expensive. Custom glassware (quartz or boro) can be even more expensive. I prepared drawings of what I wanted then sent them
out for bid to 3 suppliers. The successful bidder was half the cost of the high bidder.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Bikemaster
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@ Magpie
Have you ever try galiper slider grease(car brake) for high temperature joint sealer?? They says that the grease can withstand 850 C. I have no idea
of the reactivity with sulfuric acid or sulfur trioxide, but i don't this that it is compose of any organic compound.
What happen with the ceramic test tubes??
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Magpie
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Quote: Originally posted by Bikemaster  | @ Magpie
Have you ever try galiper slider grease(car brake) for high temperature joint sealer?? They says that the grease can withstand 850 C. I have no idea
of the reactivity with sulfuric acid or sulfur trioxide, but i don't this that it is compose of any organic compound.
What happen with the ceramic test tubes?? |
Hello Bikemaster. No, I don't know anything about that brake grease. Maybe it's MoS2? I'm going to look locally for some 325mesh graphite today as
the graphite I have is only 80 mesh - way too coarse. And you can't grind it in a mortar. Maybe a ball mill would work, but my ball mill is not
clean enough.
The ceramic tubes are resting comfortably in a storage closet. They are just waiting for me to resume my phosphorus experiments. 
The single most important condition for a successful synthesis is good mixing - Nicodem
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hissingnoise
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Simply scribbling graphite from a soft (8B) pencil onto joints might suffice.
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metalresearcher
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What about the 'Haldenwanger' porcelain crucibles (with a lid glued with the abovementioned kit or 'stove glue') to use as a retort ? In an electric
(Kanthal) furnace of course.
These crucibles withstand 1050oC.
[Edited on 2011-1-10 by metalresearcher]
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The WiZard is In
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| Quote: Originally posted by Magpie | @garage chemist
My plan was to leave the joints unlubricated. I have no ptfe liners. I do just happen to have acquired some graphite powder, however, so will use
that as you suggest. |
How 'bout "Motor Mica" extremely fine ground mica commonly used
as a dry lubricant. I use it to lube cartridge cases when reloading
ammo.
Humm Motor Mica seems to have disappeared from the market. Have found this —
http://www.midwayusa.com/Search/#motor%20mica____-_1-2-4_8-1...
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Sedit
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Woelen the fire cement more then likely would prove problematic since most of the same stuff I have is Sodium Silicates which on firing converts to
Silica Dioxide meaning you will more then likely have issues with it holding form at first on the initial firing. Making a form may be helpful perhaps
coating a tin can and firing then firing it slowly till it converts then touching up cracks and what not until you achive an air tight retort.
I personally would go with ceramics before attempting to use the fire cement and just using the cement to seal up the openings providing you with a
removable seal(it cracks easy).
I have been doing pottery for years and have considered making ceramic retorts to sell but I don't know if I would be wasting my time and if they
would sell or not.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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Sedit
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For the time being I will have to retract my statement on the Sodium Silicate forming SiO2 on heating because I can not find a reference for it and
other sites seem to suggest otherwise. This was the indication I got from studing it a while back but I am unsure if this is correct.
However its stated HERE that at 210–220 °F the sodium silicate loses water molecules to form a very powerful sealant that will not re-melt below 1500 °F which is
around 800 degress Celcius.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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Magpie
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re: my post of 8/1/11, this thread
Yesterday I made my first attempt at making SO3. Everything was going well until the furnace reached a temperature of ~860C. At this time the 19/38
joint (the lower one) began leaking. As it leaked considerable SO3 smoke was released. Since I waited too long before shutting down there was enough
smoke to challenge my efficient fume hood to the max. When the system stopped smoking I removed the quartz tube from the furnace with kaowool padded
tongs (thanks, gc) and placed it in a flower vase to finish cooling. This morning I placed this tube in a tray of water, where the Na2SO4 is quickly
dissolving.
I pushed that lower joint together manually during operation but this did not stop the leakage. So it is not a problem with the ptfe clip, which
performed admirably, suffering no damage. I believe the problem is due to the upward orientation of the male connector, which allows liquid SO3 to
form a small pool then penetrate down through the joint. The orientation should be just opposite, with the male piece on top. This mis-orientation
is an artifact of a previous design intent which was discarded.
The 24/40 connector, having proper orientation for refluxing liquid, did not leak.
So, it's back to dye making for me until I get this problem resolved.
[Edited on 12-1-2011 by Magpie]
[Edited on 12-1-2011 by Magpie]
[Edited on 12-1-2011 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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garage chemist
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I'm sorry to hear that it did not work well.
I always have a bit of leakage at the joint as well and it fumes there, but the losses are negligible.
Can you try wetting the joint with some conc. H2SO4 to help prevent SO3 from creeping through it?
Alternatively, a joint lube that's compatible with SO3 is syrupy phosphoric acid. It is convenient to let some P2O5 attract moisture until it has a
suitable consistency. If you don't have that you could boil down some 85% phosphoric acid until it is viscous enough when cool.
The problem is that very hot H3PO4 will attack quartz (not very much, but in a joint, any attack is unacceptable). You will have to keep this joint
from getting too hot with e.g. a computer cooling fan next to it. Also, you could do some preliminary experiments on the temperature at which H3PO4
starts to attack quartz.
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Magpie
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Yes, I was willing to tolerate a small leakage as long as my hood fan was handling it. But I waited way too long and I had a large leak. I strongly
recommend not letting that happen!
I have my glassware all washed up now. Last night the offending joint seemed locked as I couldn't open it. This morning it came apart easily.
Thanks for the suggestions. I may try the con H2SO4 as a joint sealant. I would hate to have to go back to my glassblower with a new design.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Magpie
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re: my 8/1/11 post
This is a progress report on my quest for SO3. After thinking about my recent failure for a few days I decided to give it another try. This time I
prepared Na2S2O7 first and used it as precursor. I did this for the same reason Len did: I didn't want to have to manipulate my quartz extension
tube during operation at 460C.
To prepare the Na2S2O7 I first dried NaHSO4 at 150C in a drying oven for 1 hour to drive off unbound moisture. I then loaded a 25x200mm borosilicate
test tube to the 125mm mark with 71.6g of the dried NaHSO4, placed it in my tube furnace, and slowly (over 4 hours) heated it up to 460C. It was
clear that H2SO4 and likely SO3 was being given off during this heating. In fact there was so much smoke coming off that I shut off the furnace
promptly upon reaching 460C. The cooled salt was very dense having shrunk in length by half with a final weight of 66.8g. Coincidentally or
otherwise this weight corresponded almost exactly to the theoretical weight of Na2S2O7. I had to break the test tube to recover the salt (I won't use
that method again), crushed it with a hammer, then ground it to a powder in a mortar.
Today this Na2S2O7 was loaded into the quartz setup as shown in the picture of my 8/1/11 post above. 98% H2SO4 (reagent grade) was used to seal the
two connectors. A slow heat-up was then begun in anticipation of making SO3. Everything was progressing well until the temperature reached about
600C. At this time a drop of liquid would periodically seep out of the lower joint. It did not fume so I assume it was H2SO4. The the upper joint
started leaking smoke, presumably SO3. So I shutdown the furnace.
Other than sealing the joints, here are improvements I would make for future runs:
1. Insulate the quartz tube up to the bend. This will prevent refluxing liquid from dripping back into the furnace tube.
2. Cut off my extension tube 25-50mm so that it is never submerged in accumulating liquid in the receiver. This will eliminate back-pressure and
eliminate any chance of suckback, a potentially disasterous event. In lieu of this the furnace could be raised 25-50mm with blocks.
To solve the leaking connectors issue I am first planning to go back to fine graphite for the upper connector. For the lower connector I am planning
on fusing this to a solid connection with sodium silicate solution. I will be able to fire this to nearly 1300C in the tube furnace which I hope will
provide a leakproof seal. If it doesn't I will be forced to go back to my glassblower with a corrected design.
Any questions, comments and/or suggestions are welcomed.
[Edited on 20-1-2011 by Magpie]
[Edited on 20-1-2011 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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Magpie
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This is another update on my adventures with SO3. I decided I needed to step back and get to know this treacherous creature a little better before
further attempts at capture. I did some small crucible testing with a Mekker burner on MAPP gas where I was just able to drive off all the SO3 at red
heat. I also attempted to drive SO3 out of some hydrated Al2(SO4)3 with absolutely no SO3 evolution. I experimented with making Na2S2O7 using a sand
bath (my first one). But the product was so hard I wasn't sure I could get it out of the ceramic dish.
Then I gave the NaHSO4 another try in the quartz tube set-up, with the lower joint sealed with RTV silicone and the upper joint as bare glass. The
upper joint leaked profusely so this run was aborted at about 570C.
On the next try (#3) I rubbed the upper glass joint, inner and outer surfaces, to saturation with extrafine dry graphite, which is available at some
hardware stores. This proved, after a little initial leaking, to provide an excellent seal. So I was on my way to making SO3 as shown in the first
picture. This arrangement was assembled with the intended use of the SO3 in mind, ie, gassing it with HCl to make chlorosulphonic acid. The
condenser was a contingency that proved to not be of much use. At T=572C I sucked out the few mls of water in the receiver using a Pasteur pipet. At
T=652 smoke was showing in the angle bend. At 682C no more smoke, just a very thin stream of clear liquid slowly running into the receiver, ie,
liquid SO3. As heating continued more SO3 was accumulating as white crystals in the receiver. Then the RTV began to deteriorate, which discolored
the liquid SO3 to a brown color. Also I noted that the end of the 8mm ID tube was plugging with solidified SO3. Although I could not reach this
location with the heat gun I warmed the falling liquid in the tube just above the flask with the gun. This was successful in clearing out the plug.
I continued the heat up to 900C. At this point there seemed to be very little product forming so I turned off the furnace.
I consider this synthesis mostly a success with the brown contamination of the SO3 the only detraction. It is obvious that good sealing of any
joints is essential. I will next try removing the RTV and replacing it with a permanent seal using sodium silicate.
My charge of NaHSO4 was 100g. I'm estimating by eye that there may be about 10g of SO3 in the 250ml RBF receiver. I will be able to report this
accurately only at a later date as I neglected to tare the receiver.
 
The single most important condition for a successful synthesis is good mixing - Nicodem
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garage chemist
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I would recommend against permanently sealing the joints with sodium silicate. The silicate has a much greater coefficient of expansion than the
quartz glass, and such a sealed joint would very likely crack upon heating or cooling.
Try the polyphosphoric acid before resorting to such a desperate measure- or just order a 90° bent 8mm quartz glass tube with one male joint, as I
have done. That way, there is only one joint in the setup, and it's facing upwards so that no liquid can leak through it.
Discoloration of the crude SO3 is not an indicator of low quality. I often had that happen due to residual vaseline on the joints of my glassware- it
turns into black goop that runs down into the liquid SO3 and makes it deep brown or black. A simple redistillation renders it clear again.
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Magpie
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@garage chemist -
Do you think I could gas the discolored SO3 first with HCl? This would eliminate vessel transfers and reduce the number of distillations to
one.
[Edited on 28-1-2011 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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