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Author: Subject: Mishap - Pyrex jugs can't withstand heat from a butane blowtorch
entheologist
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[*] posted on 31-3-2017 at 03:14
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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[*] posted on 31-3-2017 at 04:10


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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[*] posted on 31-3-2017 at 05:48


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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[*] posted on 31-3-2017 at 06:02


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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[*] posted on 31-3-2017 at 06:03


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.




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[*] posted on 31-3-2017 at 06:09


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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[*] posted on 31-3-2017 at 06:28



'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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[*] posted on 31-3-2017 at 08:44


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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[*] posted on 31-3-2017 at 11:00


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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[*] posted on 31-3-2017 at 11:38


Set the flask on wire gauze, held by a ring on a stand, burner underneath.
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[*] posted on 31-3-2017 at 13:05


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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[*] posted on 31-3-2017 at 13:23


Quote: Originally posted by Booze  

Yes. How could I make the flame not touch the flask but still have high temperatures?


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]




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[*] posted on 31-3-2017 at 14:27


Quote: Originally posted by Hexavalent  
Quote: Originally posted by Booze  

Yes. How could I make the flame not touch the flask but still have high temperatures?


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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[*] posted on 31-3-2017 at 17:16


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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[*] posted on 1-4-2017 at 07:14


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.




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[*] posted on 2-4-2017 at 05:33


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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[*] posted on 2-4-2017 at 11:05


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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[*] posted on 2-4-2017 at 16:08


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.




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[*] posted on 2-4-2017 at 18:56


This guy seems to have found a good solution:

https://www.youtube.com/watch?v=QKFC0ke_DOU
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[*] posted on 3-4-2017 at 03:45


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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[*] posted on 3-4-2017 at 04:08


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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[*] posted on 3-4-2017 at 15:26


Lol. Did it say "microwave safe, no broiler, no stovetop" on the bottom? No blowtorch is implied
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[*] posted on 4-4-2017 at 05:13


Quote: Originally posted by PirateDocBrown  
Set the flask on wire gauze, held by a ring on a stand, burner underneath.


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.




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[*] posted on 8-4-2017 at 07:21


Quote: Originally posted by DrP  
Quote: Originally posted by PirateDocBrown  
Set the flask on wire gauze, held by a ring on a stand, burner underneath.


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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