entheologist
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Mishap - Pyrex jugs can't withstand heat from a butane blowtorch
My stove and cooker were in use and my hotplate is at a friends house so I tested out an alternative method of evaporating a solution of a carbonate
salt. I used a steel pot to make a water bath, and added the solution to a pyrex jug and put it in the water bath. I used a butane blowtorch as a
heatsource. I started heating the sides of the steel pot with the blowtorch but it wasn't enough to get the water boiling, so I instead blow torched
the water inside the pot knowing that some of the heat would be rapidly transfered to the pyrex jug. That worked, the contents of the jug started
boiling, but not evenly, only on one side, so I rotated. The jug shattered. Blow torching borosilicate boiling flasks works just fine, but pyrex jugs,
no.
If I ever do that again, I'll use an oil bath and only heat the sides of the stainless steel bath, never let the heat source get too close to the
glass.
[Edited on 31-3-2017 by entheologist]
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anewsoul
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I would avoid blowtorching any glass regardless if it is borosilicate or pyrex or whatever. Anyways, was the pyrex jug laboratory pyrex? I've heard
that the pyrex glass dishes made for cooking aren't even pyrex anymore.
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Deathunter88
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Quote: Originally posted by entheologist  | My stove and cooker were in use and my hotplate is at a friends house so I tested out an alternative method of evaporating a solution of a carbonate
salt. I used a steel pot to make a water bath, and added the solution to a pyrex jug and put it in the water bath. I used a butane blowtorch as a
heatsource. I started heating the sides of the steel pot with the blowtorch but it wasn't enough to get the water boiling, so I instead blow torched
the water inside the pot knowing that some of the heat would be rapidly transfered to the pyrex jug. That worked, the contents of the jug started
boiling, but not evenly, only on one side, so I rotated. The jug shattered. Blow torching borosilicate boiling flasks works just fine, but pyrex jugs,
no.
If I ever do that again, I'll use an oil bath and only heat the sides of the stainless steel bath, never let the heat source get too close to the
glass.
[Edited on 31-3-2017 by entheologist] |
You should never ever ever ever heat glassware with a direct flame, and DEFINITELY not a blowtorch! You got lucky with your boiling flasks there,
since they didn't break. Also, what were you thinking heating a flask immersed in water with a torch? The glass above the water line will heat up very
quickly to several hundred degrees, but the water will remain below 100 degrees at all times. The slightest disturbance will cause some water to
splash up onto the super heated glass and its going to break due to thermal difference of a few hundred degrees.
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Melgar
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If you really need to apply direct heat, use a heat gun. Non-borosilicate glass can typically withstand the low setting, but has cracked on the high
setting for me. Borosilicate glass can hold up to both the low and high settings.
As far as your post, I doubt many people here are surprised, mostly because so many of us have done similar things in the past until we learned
better.
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Lambda-Eyde
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This is common knowledge and has been reported on the forum earlier IIRC. You should absolutely never heat a """Pyrex""" (it's not) anything, and you
should never ever heat a glass jug made of >5 mm thick glass no matter what brand it is. It is simply not suitable for this application and if you
continue to misuse them like this it's just a question of time before you lose an eye or end up bleeding out alone on the floor of your lab (I'm
slightly exaggerating but you get my point). Let it stay in the kitchen where it belongs, buy some real lab glass, read up on the properties of glass
and you will understand all this much easier.
Heating a Pyrex/Duran/Kimax/any other quality brand RBF, beaker or whatever with an open flame is perfectly fine if you know what you're doing.
This just in: 95,5 % of the world population lives outside the USA
Please drop by our IRC channel: #sciencemadness @ irc.efnet.org
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JJay
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I like quartz. You can heat quartz with a blowtorch until it's glowing and then quench it in cold water. Try doing that with borosilicate glass....
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yobbo II
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'Pyrex' jugs from the wallmart etc are not borosilicate but heat treated thick glass with lots of internal strain to make them 'heat resistant'.
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Texium
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Thread Moved
31-3-2017 at 07:17 |
Booze
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| Quote: Originally posted by Deathunter88 | | Quote: Originally posted by entheologist | My stove and cooker were in use and my hotplate is at a friends house so I tested out an alternative method of evaporating a solution of a carbonate
salt. I used a steel pot to make a water bath, and added the solution to a pyrex jug and put it in the water bath. I used a butane blowtorch as a
heatsource. I started heating the sides of the steel pot with the blowtorch but it wasn't enough to get the water boiling, so I instead blow torched
the water inside the pot knowing that some of the heat would be rapidly transfered to the pyrex jug. That worked, the contents of the jug started
boiling, but not evenly, only on one side, so I rotated. The jug shattered. Blow torching borosilicate boiling flasks works just fine, but pyrex jugs,
no.
If I ever do that again, I'll use an oil bath and only heat the sides of the stainless steel bath, never let the heat source get too close to the
glass.
[Edited on 31-3-2017 by entheologist] |
You should never ever ever ever heat glassware with a direct flame, and DEFINITELY not a blowtorch! You got lucky with your boiling flasks there,
since they didn't break. Also, what were you thinking heating a flask immersed in water with a torch? The glass above the water line will heat up very
quickly to several hundred degrees, but the water will remain below 100 degrees at all times. The slightest disturbance will cause some water to
splash up onto the super heated glass and its going to break due to thermal difference of a few hundred degrees. |
Really? I use a bunsen burner all the time for distillations. I am heating a round bottom with this and have done it many times. If I shouldn't do
that, then how should I heat the boiling flask?
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anewsoul
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| Quote: Originally posted by Booze |
Really? I use a bunsen burner all the time for distillations. I am heating a round bottom with this and have done it many times. If I shouldn't do
that, then how should I heat the boiling flask? |
Is the flame directly touching the flask? If not it should be fine.
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PirateDocBrown
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Set the flask on wire gauze, held by a ring on a stand, burner underneath.
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Booze
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| Quote: Originally posted by anewsoul | | Quote: Originally posted by Booze |
Really? I use a bunsen burner all the time for distillations. I am heating a round bottom with this and have done it many times. If I shouldn't do
that, then how should I heat the boiling flask? |
Is the flame directly touching the flask? If not it should be fine. |
Yes. How could I make the flame not touch the flask but still have high temperatures?
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Hexavalent
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When heating glassware, the cardinal rule is to heat evenly.
A better option would be to invest in a flat-bottomed flask and then use your Bunsen burner with a ceramic-centered gauze pad. This affords much
better and safer heat distribution than naked flames on glass, which should be avoided where possible since they are a very "concentrated"/localised
heat source. An even better idea would be to invest in a hotplate and use a water/oil/copper shot bath. These things have been discussed ad
nauseam on the forum, UTFSE. Even better is a "Drysyn" adapter which are specifically made for the purpose, but have the disadvantage of only
really being compatible with one size RBF (aside from being expensive). A chemist can but dream.
What kind of materials are you distilling for "high temperatures" to be required? I can only pray you're not distilling flammable liquids with naked
flames directly heating the glass.
[Edited on 31-3-2017 by Hexavalent]
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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Booze
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| Quote: Originally posted by Hexavalent |
When heating glassware, the cardinal rule is to heat evenly.
A better option would be to invest in a flat-bottomed flask and then use your Bunsen burner with a ceramic-centered gauze pad. This affords much
better and safer heat distribution than naked flames on glass, which should be avoided where possible since they are a very "concentrated"/localised
heat source. An even better idea would be to invest in a hotplate and use a water/oil/copper shot bath. These things have been discussed ad
nauseam on the forum, UTFSE. Even better is a "Drysyn" adapter which are specifically made for the purpose, but have the disadvantage of only
really being compatible with one size RBF (aside from being expensive). A chemist can but dream.
What kind of materials are you distilling for "high temperatures" to be required? I can only pray you're not distilling flammable liquids with naked
flames directly heating the glass.
[Edited on 31-3-2017 by Hexavalent] |
Sulfuric acid. Are those things the brown colored heating mantles? I would buy one if I already hand't got a bunsen burner.
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LD5050
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Bunsen burners suck... Invest in a hot plate, I bought one for 130 bucks on amazon and it works great! When I distill H2SO4 I use my home made heating
mantle (I do not recommend this but it works for me) I took some nichrome wire out of a glass top stove ( you can also use wire out of a hair dryer)
and got me some plaster of paris. I mixed up the plaster to the consistency of peanut butter and then took a 1000ml RBF and molded the plaster all
around half way up the flask. While it was still wet I took the wire and I wrapped it around in a coil pattern all throughout the wet plaster, I let
this dry. Also I made sure I left enough wire coming out of the plaster at both ends to hook up to power.
After it dried I got a plug from an old lamp and cut it off, I then stripped the wires at the end and hooked up to extruding wires from dry plaster
mantle. I plugged this in to finish the drying process. It gave off a lot of steam and eventually dried out completely. After, I found a pale of the
size I wanted and filled this with wet plaster. I placed the dry molded heating mantle I made inside the bucket. I let this dry and removed from the
bucket to leave a perfectly molded solid plaster heating mantle that work GREAT!
I use this for when I need really hot temps like for distilling H2SO4 but other than that my 130 dollar hot plate works fine for everything else. You
can also find cheap heating mantles on ebay with built in magnetic stirrers, I assume they work fine because Dougs Lab from ebay uses them.
I used my home made heating mantle a bunch of times before it started to crack it holds up really well. I just don't recommend it because A- im not an
electrician and B- distilling H2SO4 is extremely dangerous!! if the mantle gets a hot spot and cracks your flask while distilling you're F$*@ED!!!
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Hexavalent
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DrySyn adapters are metal blocks with bowl-shaped "depressions" which RBFs fit very snugly into. They essentially turn a standard hotplate into a
heating mantle which has the benefit of very uniform heating.
I have to concur with LD5050. Distilling sulfuric acid isn't something to be taken lightly. Boiling concentrated sulfuric acid is extremely unpleasant
and requires a great deal of care and experience to handle safely. I don't want to turn this into a lecture, but you must walk before you run. Learn
the principles of distillation thoroughly, learn to diagnose problems, and gain experience with more innocuous liquids first before attempting this.
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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yobbo II
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If you must use a flame put some sand in a biscuit tin and put that between the torch and container/flask.
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Booze
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| Quote: Originally posted by LD5050 | Bunsen burners suck... Invest in a hot plate, I bought one for 130 bucks on amazon and it works great! When I distill H2SO4 I use my home made heating
mantle (I do not recommend this but it works for me) I took some nichrome wire out of a glass top stove ( you can also use wire out of a hair dryer)
and got me some plaster of paris. I mixed up the plaster to the consistency of peanut butter and then took a 1000ml RBF and molded the plaster all
around half way up the flask. While it was still wet I took the wire and I wrapped it around in a coil pattern all throughout the wet plaster, I let
this dry. Also I made sure I left enough wire coming out of the plaster at both ends to hook up to power.
After it dried I got a plug from an old lamp and cut it off, I then stripped the wires at the end and hooked up to extruding wires from dry plaster
mantle. I plugged this in to finish the drying process. It gave off a lot of steam and eventually dried out completely. After, I found a pale of the
size I wanted and filled this with wet plaster. I placed the dry molded heating mantle I made inside the bucket. I let this dry and removed from the
bucket to leave a perfectly molded solid plaster heating mantle that work GREAT!
I use this for when I need really hot temps like for distilling H2SO4 but other than that my 130 dollar hot plate works fine for everything else. You
can also find cheap heating mantles on ebay with built in magnetic stirrers, I assume they work fine because Dougs Lab from ebay uses them.
I used my home made heating mantle a bunch of times before it started to crack it holds up really well. I just don't recommend it because A- im not an
electrician and B- distilling H2SO4 is extremely dangerous!! if the mantle gets a hot spot and cracks your flask while distilling you're F$*@ED!!!
|
Because everyone is telling me to get a hot plate stirrer, FINE, i'll get one. Also, because this is a science website and I am a nerd, I will point
out that before you steamed the plaster it did not "dry", it simply hardened. The silica fibers encase the water. So there, that's kinda how plaster
works.
The first time I tried to distill H2SO4 I used a normal hot plate- and spoiler alert, it didn't work. Although it did get rid of a little water and
burned the addatives away.
At one point I did have a homemade heating mantle I made with heat tape and wire, but that melted my 500 mL RBF and just gave me a bunch of sadness.
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battoussai114
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Unless you're practicing your glassblowing skills, put the torch down.
Regarding diy heating mantles, it doesn't take much more than understanding Ohm's law and knowing how to follow instructions. So saying it's not
recommended is a bit too much. If you want to go on the safe side go and copy what NurdRage did in his video, if he's still alive you'll probably be
too.
Batoussai.
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PirateDocBrown
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This guy seems to have found a good solution:
https://www.youtube.com/watch?v=QKFC0ke_DOU
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BromicAcid
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The bigger the piece of glassware, the more even heating you need. Even borosiliate glass isn't immune to thermal shock. Larger flasks (50L and 72L)
have this stamped right on the flask to heat them slowly and evenly. There is also the issue with the shape of the container, hard edges are areas
where stress can accumulate, generally you have to play a bit nicer with them to prevent issues.
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Elemental Phosphorus
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Honestly, if you are on a tight budget I would recommend a sand bath to boil the sulfuric acid, and you can flame heat the sand bath to get a higher
temperature. This has 2 advantages; sand is cheap, and if something goes wrong you won't end up with hot oil everywhere.
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Alkemist
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Lol. Did it say "microwave safe, no broiler, no stovetop" on the bottom? No blowtorch is implied
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DrP
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I was going to say the same and suggest starting with a yellow flame and slowing bringing the temperature up.. that's what we used to do with Bunsen
burners... although I suspect no-one uses them anymore, lol.
\"It\'s a man\'s obligation to stick his boneration in a women\'s separation; this sort of penetration will increase the population of the younger
generation\" - Eric Cartman
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Booze
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| Quote: Originally posted by DrP |
I was going to say the same and suggest starting with a yellow flame and slowing bringing the temperature up.. that's what we used to do with Bunsen
burners... although I suspect no-one uses them anymore, lol. |
I do! It is an easy way for quick heat.
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