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peach
Bon Vivant
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Yeah, I'd agree with anomonus, sealing that was a bad idea.
I've never had a conical break under vacuum, or heating, despite going through a period of using them solely on a regular basis. Good luck is very
random in it's occurrences.
{penises}
I saw a documentary all about extreme body modification. It started getting 'a bit dodgy' with the implanted crufices on the forehead, then went
further and started with bisected penises. The doctor's reaction on seeing the photos was perfect. Pure silence for a few seconds then... "I suppose,
if you're thinking of doing this, you really should consider psychiatric help".
There are also guys on the net cutting theirs off at home, for reasons entirely unknown to me.
For a real cringe, have a look for videos of emasculating livestock. One of them involves something that looks like a pair of pliers and a cordless
drill. The 'pliers' are in the chuck. Guess the rest of that. It involves spinning.
[Edited on 18-10-2010 by peach]
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aonomus
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Um, I'll pass. This has nothing to do with bad days in the lab or with glassware. [/derail]
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peach
Bon Vivant
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I'm afraid I agree with the reply much earlier on in the thread, suggesting this was a bit of a silly question to start with.
Experiments gone wrong? The list is gigantic.
And reading someone else's opinions on the finer details of one specific situation won't stop a complete beginner from making the same mistakes,
unless it's a very specific question.
I have two bits of advice regarding glassware.
1.) Don't keck clip the entire thing, and think about where you put them. I've had water back syphon when I was first distilling sulphuric, hit the
sulphuric near 98% and 300C+, then blow a Hollywood style volcano out of one of the ports. Lucky for me, I'd left that one unclipped for that reason,
as the flasks may have popped instead.
2.) If you have a big stretch of condenser and a big flask filling up on the other end, use a ball / cup joint at the still head so the condensing
section has some degree of movement. A lab jack is good, but a ball / cup joint is cheaper and provides genuine flexibility and 100% clamping. A lab
jack will still leave the glass strained to some degree, whereas the joint will let you rigidly clamp both the receiver and the starting point, with
it taking up the error and strain. You'll see the cold fingers on rotovaps often have a ball / cup on the receiver flask for that reason, so the
weight of the solvent can find it's own centre of gravity without snapping the joint. They also feature as permanent joints on the more expensive,
large scale glass.
You can get ball / cup adaptors that go onto the straight tapers to add the 10-15 degrees of flex. Don't over tighten them, they'll never be rigid,
they're not supposed to be, you'll just break it.
[Edited on 19-10-2010 by peach]
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Magpie
lab constructor
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I recently had a bad day with my buret. It hit the frame as I was removing it from my hood and I dropped it. I have a rubber mat on the floor so
breakage happened only when it hit the cabinet on the way down.
The top 1" was broken off jagged but I trimmed that edge clean with a diamond wheel Dremel tool. As you can see I also broke the tip off. It is
useable with a Scotch tape splice but I'd like to fuse it by glassblowing. I'm pretty sure it is borosilicate.
I would like to ask the experienced glassblowers if they think this is advisable. My glassblowing skills are rudimentary. For tools I have propane,
MAPP gas, a regular bunsen burner, and a Meker burner.
Edit: Th ID of the tip at the break is ~2mm.
What do you advise?
[Edited on 3-12-2010 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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watson.fawkes
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Quote: Originally posted by Magpie  | I would like to ask the experienced glassblowers if they think this is advisable. My glassblowing skills are rudimentary. For tools I have propane,
MAPP gas, a regular bunsen burner, and a Meker burner.
Edit: Th ID of the tip at the break is ~2mm. |
I'm just guessing that you might want to work glass
generally. Just guessing. If you don't, send it out for repair or scrap it. The ante for any (sane) glassworking in borosilicate is eye protection.
Expect to drop on the order of $100 for something adequate. And then you can start spending more.
Get some 2 mm ID tubing and practice on that. Your first butt joints won't be adequate. For instruction, there are a number of out-of-copyright books
that adequately show how to do this.
You'll likely need a finer flame than the burners you've got. You'll have an issue holding the small end while rotating it, even with a smaller flame.
You may need to make a jig.
Propane/oxygen will be fine; propane/air may well not be hot enough.
There's more, if you want to go down this road.
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UnintentionalChaos
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Am I the only one who seems to keep breaking Keck clips? I've got some of the cheap off-brand ones and some good quality ones and neither seems to be
immune to breaking. I own a 4-neck 1L flask and a 1-neck 1L as my largest flasks. Whenever I need more than one neck (like now), I have to stopper all
the spare necks on the 4-necker. Now, being that constant breakage has my keck stock pretty low, I just left some of them with a heavy amount of
grease while distilling off azeotropic HCl. So far, I've had 2 different episodes (over ~13hrs of distillation) where they've blown loose, spraying
hydrochloric acid fumes into the air and getting droplets in the oil bath. This has forced me to move all the semi-available keck clips to the
distillation flask.
As I was cleaning up the last one, the keck clip holding the recieving flask simply broke in half and fell onto the bench. I have no spares, but it is
sitting firmly against a solid surface now (and I'm not under exclusion of air, so that's a non-issue).
I've looked into metal kecks, but they're a fortune when you'd need to buy 10 or so.
Aside from that, this distillation is infuriatingly slow. Even turned way up, and with wads of insulation, I can't squeeze enough power from my
Corning PC-351 hotplate/stirrer to get a good distillation rate on anything water based. I'm getting less than a drop per second which makes reagent
prep maddening.
[Edited on 12-4-10 by UnintentionalChaos]
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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Magpie
lab constructor
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Thanks watson for your reasoned advice about repairing my buret. I don't really want to take on glassblowing so will live with what I have (Scotch
taped) until I find a bargain on eBay. It seems like you can't even buy a decent glass buret for under $50-$100 on the open market. I'm sure I
didn't pay over $25 for mine on eBay but that was some time ago.
I've ruined quite a few of the cheaper Keck clips, usually by overheating. I bought some Teflon clips that are quite beefy and a lot better, and will
take a higher temperature too. But they are quite spendy.
In school we had some ss clips that used a spring, but I've never seen them for sale anywhere. I've been toying with the idea of making my own out of
ss308 3/32" TIG welding wire. Garage chemist has some ss clips but I can't tell (from his pictures) if they are purchased or homemade.
The single most important condition for a successful synthesis is good mixing - Nicodem
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watson.fawkes
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| Quote: Originally posted by Magpie | | Thanks watson for your reasoned advice about repairing my buret. I don't really want to take on glassblowing so will live with what I have (Scotch
taped) until I find a bargain on eBay. |
You can use a cyanoacrylate glue for a non-permanent repair, assuming
the break is clean.
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UnintentionalChaos
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| Quote: Originally posted by Magpie | Thanks watson for your reasoned advice about repairing my buret. I don't really want to take on glassblowing so will live with what I have (Scotch
taped) until I find a bargain on eBay. It seems like you can't even buy a decent glass buret for under $50-$100 on the open market. I'm sure I
didn't pay over $25 for mine on eBay but that was some time ago.
I've ruined quite a few of the cheaper Keck clips, usually by overheating. I bought some Teflon clips that are quite beefy and a lot better, and will
take a higher temperature too. But they are quite spendy.
In school we had some ss clips that used a spring, but I've never seen them for sale anywhere. I've been toying with the idea of making my own out of
ss308 3/32" TIG welding wire. Garage chemist has some ss clips but I can't tell (from his pictures) if they are purchased or homemade.
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I can buy metal ones on ebay here ($9USD!! each  ), but I've never seen the PTFE
ones. Just did a bit of research, looks like they're made for quickfit. Do you know offhand if quickfit sizes are compatible with US standard taper?
I think the answer is yes, but I'm not entirely sure.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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Magpie
lab constructor
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Here's where I bought mine, a pkg of 5, part no. 89026-174 for size 19. I see they have other US sizes in the other part no. shown.
https://www.vwrsp.com/psearch/ControllerServlet.do?D=89026-1...
If you want to see what they look like see:
http://www.sciencemadness.org/talk/viewthread.php?tid=14768#...
The single most important condition for a successful synthesis is good mixing - Nicodem
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psychokinetic
National Hazard
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I'm sure someone mentioned the ability to google up there somewhere . . .
“If Edison had a needle to find in a haystack, he would proceed at once with the diligence of the bee to examine straw after straw until he found
the object of his search.
I was a sorry witness of such doings, knowing that a little theory and calculation would have saved him ninety per cent of his labor.”
-Tesla
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jtalmodovar26
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Accidentally took a huge whiff Ammonia and a collection of Iron Chlorides. My Eyes stung for awhile
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kuro96inlaila
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I don't know what to say,am I cursed or something?
Everytime I use an evaporating dish,sure it will broke!
Everytime............
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Magpie
lab constructor
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Are you heating it with a bare flame?
The single most important condition for a successful synthesis is good mixing - Nicodem
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jtalmodovar26
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Yeah, I thought You were supposed to put a metal screen inbetween the dish and the flame?
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Magpie
lab constructor
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That's what I have concluded too. I broke my 6" dish that way.
Also, I was heating some solids which hadn't yet liquified so heat transfer was poor and uneven.
The single most important condition for a successful synthesis is good mixing - Nicodem
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kuro96inlaila
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No,I heat it on a wire gauze.
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Magpie
lab constructor
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Sorry for the mixup.
So you are using a wire gauze. Are you heating a liquid or a solid? Are you bringing up the temperature gradually and evenly?
Or, tell us what you are doing. It's always easier to address a problem when we know the details.
The single most important condition for a successful synthesis is good mixing - Nicodem
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kuro96inlaila
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Hm,I usually heat a liquid in it,
maybe temperature shock cause it to broke,
but I expect porcelain didn't have problem with that,
or does it?
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bob800
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Does VWR sell to individuals?
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Magpie
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equipment, yes
[Edited on 2-1-2011 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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watson.fawkes
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All ceramics can be
thermally shocked into breaking. Some are more resistant than others.
A very simple sand bath can ameliorate this: a metal plate with a rim, 1/2" of sand, evaporating dish on top. Increasing the thermal mass and the
thermal conduction pathway evens out the heating profile at the cost of using a bit more heat.
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bob800
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| Quote: Originally posted by Magpie | | It seems like you can't even buy a decent glass buret for under $50-$100 on the open market. I'm sure I didn't pay over $25 for mine on eBay but that
was some time ago. |
Cynmar has some Class B teflon-valve and Class A glass-valve burets for <$20:
http://www.cynmar.com/item_detail.aspx?ItemCode=11520624.
http://www.cynmar.com/item_detail.aspx?ItemCode=11520660
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kuro96inlaila
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| Quote: Originally posted by watson.fawkes | All ceramics can be
thermally shocked into breaking. Some are more resistant than others.
A very simple sand bath can ameliorate this: a metal plate with a rim, 1/2" of sand, evaporating dish on top. Increasing the thermal mass and the
thermal conduction pathway evens out the heating profile at the cost of using a bit more heat. |
Thanks for the information!
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peach
Bon Vivant
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I can 100% confirm that borosillicate can be thermally shocked into shattering.
The smaller the glass is, and the simpler, the less and less likely it becomes. But, when working with multiple litres, or tens, it will shatter if
it's not warmed and cooled uniformly and gently. The specific heat capacity of the liquid is another thing. I mean, to warm up a volatile solvent you
will need very little energy, but something like water means there's a big, cold heat sink on the other side of the glass, and a thousand degree flame
on the other.
For example, if you're working with ten litres of cold / RT water, that will take a long time to warm up to boiling, and a lot of energy. You really
want to be using a mantle specifically for that size of flask, a big bath or a heating jacket of some form.
With 10's of mls (as you'd work with at school when 16-18), I can stick blow torches directly on the glass and it's fine.
I was in Italy at one point and the tour boat took us to a decorative glass blowers. The guy made a little horse, like you'd see on a Ferrari, then
set it on the bench in front of us as he got going on something else. Around a minute later, as it cooled, it shattered into a broken pile on the
desk.
Painful glassware incidents;
- Bursting a 10l flask
- Forgetting to weigh down my clamps and leaving a distillation to run. The receiver filled up, altered the weight distribution and toppled the
vigreux, still head, condenser, vacuum receiver bend and receiver flask. I'm not sure which shattered more, the receiver bend or my heart.
- I have also broken two evaporating dishes, but through needing to tidy up / take more care rather than heat. If you're dish is 6" and reasonably
tall, and filled with cool liquid, and being heated by a bunsen, it may be that you're simply applying too much heat too quickly. If you can, turn the
gas down and set the flame so it's just going blue, to warm it more gently. Another simple solution is to not try warming so much at once. Pour SOME
of your solution in and let it warm, then add the rest in portions until it's done. Filing glass too high from the start creates another major problem
- wiping up the splashes on the surface
- Although it's never broken any glass, I am always annoyed when a solution thickens and the stir bar breaks free. It start swirling round and round
like a coaster at the fair and, the motor free wheels and starts vibrating, and the glass tries to do the washing machine dance.
All the best to all my science nerds for christmas and new years (even the ones I argue with, who are probably my best nerds),
John
[Edited on 3-1-2011 by peach]
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