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panziandi
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Could you not get hold of an old lectue bottle cylinder that has been disposed of at a salvage yard etc and fill that with SO2?
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Sauron
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The valve for SO2 needs to be stainless steel, or monel. Brass would not be wise. So the odds of finding a LB with a serviceable SS control valve are
slim. Anyway there are no such salvage yards in Thailand.
In USA LB users must dispose of empty LBs as hazardous waste. It costs about $300 per LB to do that. Linde has inaugurated a LB return program for
customers to get around that (and to steal a competitive march on Matheson, Air Products etc.)
I have been to the Thai industrial gases people and they do not stock LBs. They told me they can fill them once I have them and offered to import
Matheson LBs prefilled for me (hugely expensive.) The LBs are not so pricey, I can live with $75 in USA or $150 delivered here. But I barf on the
notion of having to pay big money for a dinky little needle valve. That is really outrageous and renders the whole affair uneconomical and
unattractive.
It does not kill the project, just the LB storage aspect. That was a luxury and as such is dispensible.
Sic gorgeamus a los subjectatus nunc.
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panziandi
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Is that from an Aldrich office? Perhaps eBay could get one? There are often regulators etc on ebay (OK usually for N2, O2, Fuel) but sometimes you
find specialtiy ones. I'm obviously not in Thailand and have NO EXPERIENCE WHATSOEVER in getting equipment from SE asia but... I know that you can
often jump to the country next door, could a Chinese gas company supply cheaper LB and regulators? I asked about the salvage yards as my local council
dump has a metal cage which people recycle cylinders at. I had empty disposable Ar cylinders and took them there to dump and noticed smaller lecture
bottles were there... I couldn't pinch one tho (mind I don't know what was / had been in them!)
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Sauron
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I detest eBay and have not been active on LabX for some time.
I don't think I'd care to muck around with Chinese or Indian control valves.
But thanks for the suggestions.
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Sauron
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Now I have quotes from two other sources, Fisher in USA and Argo in UK, for stainless steel lecture bottle manual control valves. Both quotes are in
the $170 range ($160 Fisher, 80 GBP Argo) so I think my guestiamte of a 2X factor in my local Aldrich agent's quote ($275) is about right.
What I can do is buy the LBs and/or Sure/Pac bottles from the local agent but circumvent them for the valves and buy those directly from S-A in USA
via one of my colleagues there, then have him trans-ship to me from his US location. The valves are small and light. The bottles, not so small and not
so light.
Brass valves are in the $100 range but useless for SO2 and other corrosives.
These damned valves have tripled in price in the space of 12 years. Ridiculous!
On the premise that dealing with an OEM might be more reasonable I have requested a quote from RMI Manufacturing in Livermore CA. They have a LB
control valve in 303SS, 3/8 NGT to CGA 180/110. NGT is I guess, newer nomenclature for Natl Pipe Thread. I will look it up.
NGT is National Gas Taper thread. NPT is National Pipe Taper thread. Apparently NGT is a newer standard which has a simplified gaging system
(go/no-go measuring tools for threads are called gages not gauges). I will have to look up what difference there might be between 3/8 NPT and 3/8 NGT
and if they are a mismatch then this RMI product may not be compatible (at least without an adapter) with the Aldrich LB which has a 3/8 NPTF thread.
Fortunately because of some of my former engineering work I am familiar with thread forms and this is not terra incognita.
[Edited on 4-9-2008 by Sauron]
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Natures Natrium
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https://sciencemadness.org/talk/viewthread.php?tid=4061&...
Only thing I have to add to this is that my bottle is still holding up after several years, despite having a brass control valve. Where the SO2 was
flowing across the surface it initially discolored, then did not appear to react any more. I suspect passivization.
-NN
\"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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Sauron
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That's interesting.
But the price difference between a brass control valve and a SS one is only about $50. They have gotten to be expensive, too.
I'm more interested in how you make use of your bottle. Is it a LB or more of the Sure/Pac type? Mild or stainless steel? Do you liquify your own
SO2 or do you have it refilled commercially?
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garage chemist
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I have made sulfuryl chloride via the camphor method recently, using Sartori's procedure, and it did work nicely.
A single fractionation affords a pure product, and a quite small amount (ca. 10g) of camphor can make an almost infinite amount of SO2Cl2 if you just
keep bubbling SO2 and Cl2 into the liquid simultaneously.
I found that it is very important that the reaction mixture be cooled with cold water or ice during the synthesis, as the solubility of gases in
liquids decreases with increasing temperature. If the liquid gets warm, both Cl2 and SO2 partially bubble through without reacting.
If it stays cold, the gases both get completely absorbed.
The SO2 was generated by dripping 30% HCl on potassium bisulfite, which is available extremely cheaply from ebay here (EUR 3,20/kg).
This gas generator gets very cold during operation- the SO2 evolution seems to be an endothermic process. It should be placed in a warm water bath to
counteract this and increase the rate of gas production.
If the gas generator is not warmed, only a part of the theoretical amount of SO2 is released even after all the HCl has been added- and upon swirling
or warming, suddenly very large amounts of SO2 are released, which is a bad thing.
After all the HCl has been added to the bisulfite, the gas generator should be slowly heated to about 80°C in order to release all SO2 that is still
dissolved in the aqueous KCl solution, which really is a lot.
The SO2 was dried by a CaCl2 tube. H2SO4 could be used as well.
Chlorine was produced via the usual TCCA method, and also dried with CaCl2.
I find that the camphor method is superior to the GAC method because of the simpler apparatus and visual control of the gas streams- you can see the
SO2 and Cl2 bubbles getting smaller while dissolving in the reaction mix, and the color of the head space over the reaction mix tells you if you have
chlorine in excess, which is to be avoided.
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Sauron
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Welcome back, old friend! Good to see you posting again.
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Natures Natrium
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| Quote: | Originally posted by Sauron
That's interesting.
But the price difference between a brass control valve and a SS one is only about $50. They have gotten to be expensive, too.
I'm more interested in how you make use of your bottle. Is it a LB or more of the Sure/Pac type? Mild or stainless steel? Do you liquify your own
SO2 or do you have it refilled commercially? |
I don't know the difference between LB and Sure/Pac. I'm fairly certain it is stainless steel, since it used to contain pure oxygen. The walls of
the vessel appear to be extremely thick, a cm or more.
I liquefied my own as detailed in that thread I linked to. Haven't used it much, except for a few mild reductions, and producing SO2Cl2 via activated
carbon in a 300mm leiberg condenser with water circulating. Always wanted to try the camphor method, heard from a reputable source it works extremely
well. 
I only used the brass valve because it came with one, at the shop where I bought it. Had to rig a hose barb to it via some pipe clamps and some
braided PVC hose, since I couldn't find a suitable, official adapter. Works good with no leaks, under the weak ~15PSI that the SO2 generates at 25C.
-NN
[Edited on by Natures Natrium]
\"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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Sauron
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LBs are DOT rated for 1800 spi so can handle highly compressed gases. Sure/Pac are rated 240 spi so are only suitable for for condensed gases (vapor
over liquid (with or without a dip tube). In both cases as sold by Aldrich they are mild (carbon) steel. Last year or earlier this year Aldrich also
offered stainless steel LBs but no longer. They still offer SS sample cylinders, double ended, in a variety of sizes up to 500 ml (comparable to a LB,
smaller than Sure/Pac that goes to 2.2 L.)
The SS sample bombs are much costlier.
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watson.fawkes
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The Compressed Gas Association publication CGA G-3 is their monograph on SO<sub>2</sub>. The table of contents is available for free
online.
The refrigerant designation of SO<sub>2</sub> is R-764. It was one of the first refrigerants used in residential freezers. It should be
clear that an ordinary refrigeration compressor can liquefy it and that a standard refrigerant recovery system can move it around.
All the material compatibility charts I've seen distinguish between wet and dry SO<sub>2</sub>. I seem to recall that brass is acceptable
for the dry gas.
NGT is the same basic thread form as NPT, except with more threads engaged and tighter tolerances on roots and crests. See this page for more information from a gage vendor. I presume the purpose is to allow dry assembly of the joint, avoiding spiral leaks without
thread sealing compounds.
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panziandi
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Slightly off topic but slightly related and apologies for posting here... Please keep it to a single post reply if possible or U2U so as not to cause
a branchng thread:
The disposable Argon and CO2 cylinders for mig welding such as: http://www.welduk.com/Details.asp?ProductID=90
I was studying an empty cylinder I had lying around and it looks possible to remove the non-return valve and possibly fill with liquified gas.
It does clearly state "NON-REFILLABLE" but... any ideas on whether it would be ok to open the cylinder and fill with another gas...?
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