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Varmint
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Which is why I mentioned it.
DAS
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subsecret
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Sorry, IrC. Thanks for the reminder.
On another note, I purchased a pumice scouring block at Lowe's. It's much more difficult to crush this block into small pieces, as it hitting or
crushing it simply crushes the air pockets. Boiling stones made from this material (as previously identified) work well.
Fear is what you get when caution wasn't enough.
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Magpie
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I also use little pieces of a broken clay pot.
I'm interested in the silicon carbide boiling stones commercially available. It's not that I need them for boiling stones: I need porous silicon
carbide for use as a catalyst support.
Are the silicon carbide boiling stones porous? Or do they just rely on sharp edges for use as boiling stones?
The single most important condition for a successful synthesis is good mixing - Nicodem
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testimento
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What boiling stone material would be ideal for concentrating sulfuric acid? I tried borosilicate glass shards, silica sand and curshed porcelain fuse
shells, but it just kept bumping. Havent tried silica gel yet.
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BromicAcid
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Because concentrated sulfuric acid is so dense and thick boiling stones do not do the trick. Old school capillary N2 action would likely be the best.
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Oscilllator
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Quote: Originally posted by testimento  | | What boiling stone material would be ideal for concentrating sulfuric acid? I tried borosilicate glass shards, silica sand and curshed porcelain fuse
shells, but it just kept bumping. Havent tried silica gel yet. |
I have used coke (as mentioned previously on this thread) to prevent the bumping of sulfuric acid. In my case it completely eliminated the bumping
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ZIGZIGLAR
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Can't you reuse ptfe boiling chips? I use these as they offer the flexibility of working well under vacuum, as I don't have a nitrogen or argon line ...
I've used capillary bleed tubes with success too. You can easily make them yourself by just buying 6mm OD borosilicate tube and holding the tip with
needle tip plyers, heating the end up really hot, then stretching it out until you have a thin tip, then just break/cut the end bit off. The 6mm OD
will slide comfortably through any gland designed for thermometers. If oxidation is a concern, then you're probably using a nitrogen bleed already, I
imagine.
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Refinery
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| Quote: Originally posted by Oscilllator | | I have used coke (as mentioned previously on this thread) to prevent the bumping of sulfuric acid. In my case it completely eliminated the bumping
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Can you say, is graphite essentially a pure carbon and would it be suitable for the purpose? I have a similar problem and only place I can get coke is
from industrial supply and they sell it only in 40kg bags.
And don't you get fine particles into the sulfuric acid, turning it like black goo? What do you use to filter the carbon off?
[Edited on 17-2-2014 by Refinery]
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organicchemist25
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When I first started using boiling chips I used broken up pieces of a spark plug. They worked fine. I eventually just bought two big containers of
boiling chips. They are relatively inexpensive.
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Oscilllator
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| Quote: Originally posted by Refinery | | Quote: Originally posted by Oscilllator | | I have used coke (as mentioned previously on this thread) to prevent the bumping of sulfuric acid. In my case it completely eliminated the bumping
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Can you say, is graphite essentially a pure carbon and would it be suitable for the purpose? I have a similar problem and only place I can get coke is
from industrial supply and they sell it only in 40kg bags.
And don't you get fine particles into the sulfuric acid, turning it like black goo? What do you use to filter the carbon off?
[Edited on 17-2-2014 by Refinery] |
The main property of the coke that makes it a good material for boiling chips is its extremely high porosity. Graphite is not porous, so i dont know
if graphite would be suitable for boiling chips but its worth a try. Coke is quite hard so it does not disintegrate into a black goo and because I
used chunks with a diameter of 5+mm, I can just decant the sulfuric acid off the coke.
Even though it comes in 40kg sacks, its probably worth getting one (or more!) to power a forge like the one I have. I have been able to do many high
temperature experiments with my forge (like casting copper) so it's well worth the money.
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packetforger
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We mainly use small pieces of pumice in the lab, however smashed up flowerpots is a viable alternative according to the manual that came with a
chemistry set I bought as a child.
Pieces of plates/pottery are good too, but I suspect the reason we use pumice in the college is due to the fact it is very porous, giving rise to many
nucleation sites for bubble formation to prevent the forming of hotspots and the like (instead, you get many small bubbles).
Pumice is widely available as it is used for scraping dead skin off, just buy a lump of it and hit it with a hammer to make the small pieces. Perhaps
washing it may be a good idea as it might be contaminated with some antiseptic or something (I doubt it, but better safe than sorry...)
[Edited on 21-2-2014 by packetforger]
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bfesser
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Pumice and most ceramics will scratch the hell out of your glassware. Better to stick with boiling sticks or proper boiling stones.
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ZIGZIGLAR
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Why doesn't anyone use capillary bleed tubes these days? They add the flexibility of being viable during vacuum distillation and can also be used to
introduce N2 for sensitive reactions or boiling of highly flammable solvents ...
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Oxirane
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Have you any experience on silica gel except for the one poster on the first page? I found two types of gel, the clear one for smaller pores and
larger, opaque ones as cat litter. Tried to vac distill pure some DMSO, but it started to bump so badly the whole distillation setup was gonna jump
off the table and I was afraid it could strike so hard to implode the vacuum so I immediately cut it off.
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S.C. Wack
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A problem with silica gel is that it's only so inert, but it's unsurprising that your boiling stones failed in vacuum distillation of DMSO.
I'm also a fan of the off-topic use of pulled capillaries through the thermometer hole for vacuum distillation, and have heard that a proper capillary
pulls negligible air through it, but haven't tested this with even a balloon. A fine capillary end on a stout tube can usually withstand an amazing
bumping ordeal.
[Edited on 11-10-2014 by S.C. Wack]
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Dr.Bob
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Pumice is likely softer than most boiling stones. I have a bottle of them, and I think they are made of alumina, which is quite hard and will
scratch most things well. They specifically state that they are high porosity, I think that is key, magpie, so the SiC ones are likely the same
highly porous material.
If anyone wants a small amount, I am happy to provide a little for free. Magpie, if you think Al2O3 might work, let me know and I will send you some
to test.
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Amos
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I chiefly use pieces of quartz salvaged from geodes; they're free and easy to obtain and they get the job done really well.
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Little_Ghost_again
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I use the broken ceramic tubes from the tri pod triangles, a very small bit does the job perfect!
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Refinery
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I'm pretty much betting between these three options:
1) Bleeder tube (with forced air if system is open)
2) Activated carbon granules
3) Calcium sulfate chips (prepared as gypsum, spread onto plastic/glass/al foil, chipped when dried for 24h)
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Mateo_swe
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I been looking for some reusable boiling chips and it seems they are not cheap nowadays.
500g of PTFE boiling chips would cost me almost 90 Euros on ebay.
So what is usable instead of the PTFE boiling chips?
I read broken glass pieces, small ceramic pieces or a crushed clay pots for flowers would work.
Some said crushed dinner plates works but can only be used once, it that true?
I guess i can crush some old dinner plates or flower pots and put in a jar to use when needed and if they only can be used once its ok as they cost
almost nothing.
Are any of the cheap alternatives better than the others?
[Edited on 2020-7-11 by Mateo_swe]
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pneumatician
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glass balls? I use it and work 100% easy to clean, well, sometimes hard to clean but if too hard I send to Hell
very cheap for 1kg, a lot of balls!!!
used in rectification columns!
https://duckduckgo.com/?q=Solid+Soda+Glass+Balls+columns+lab...
[Edited on 1-9-2020 by pneumatician]
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teodor
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Once I took a thick ceramic plate, smashed it with a hammer, selected pieces of proper size. They where glazed but after few boiling of acids they
become completely unglazed as well as free from metal contaminations. They serve me well. I didn't get good results with glass balls - they just don't
prevent bamping (in most cases). Unglazed porcelain has pores which are essential for smooth boiling.
[Edited on 2-9-2020 by teodor]
[Edited on 2-9-2020 by teodor]
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unionised
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I'm fairly sure that the reason people took to using capillary leaks for vacuum distillations i that boiling chips simply don't work properly.
For solvent recovery from non aggressive solutions I use a matchstick with a bit of wire wrapped round it so it sinks.
For acids I use silica gel.
I found that broken glass, while generally available in chem. labs, isn't very effective.
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pneumatician
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maybe you not use enought balls or too big. Sometimes I get a bloob but so neutralized... it's interesting to see
glazed ceramic is with lead so if you remove it is in your solvent.
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teodor
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I've made some illustration what I mean by "glazed ceramic".
I was mistaken, the glaze is still there. But after smashing there are chips which contain it only on very small surface that it is almost
unnoticeable, probably I just selected most unglazed over the time. These on picture where already used 5-15 times. I don't see any signs on wearing.
The glass balls I compare them to is of 1.5-3 mm in diameter.
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