Alastair
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A small accident
Yesterday I had a funny day. I broke 3 vessels and one of them was containing hot sulfuric acid.
I needed just a small amount of conced H2SO4 for some testing so i was distilling 30% electrolyte, about 20 grams.
When i wasnt looking a piece of glass just shot out of the vessel (and later it cracked completely ofc)
I think that happened because the amount was too small and glass started expanding differently.
I think it might be useful to remind everybody that heating a nearly empty flask is as stupid as heating an empty one, im glad i didnt use my
favourite glassware and there were only small amounts of acid, so nobody got hurt.
Heres a pic of Mr Coffee Still. RIP.
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hissingnoise
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| Quote: | there were only small amounts of acid, so nobody got hurt.
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This time . . . !
The moral of the story is; you need to drop your apparent cavalier attitude to safety!
I mean, heating H<sub>2</sub>SO<sub>4</sub> in any quantity in shit glass is begging for trouble!
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Alastair
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hey, dont insult him, he was pyrex 
but yeah, my bad, i learned from it.
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hissingnoise
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Pyrex?
Genuine borosilicate doesn't fail by reconcentrating sulphuric acid!
Two lessons learned, perhaps . . .
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watson.fawkes
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Pyrex brand consumer glassware (like a
Mr. Coffee) in the US is no longer borosilicate. Corning sold off US rights to the brand several years ago.
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starman
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You broke three pieces of glass.Same day,unrelated incidents?Perhaps you should reregister as 'Welcometothecasualtyward'.
[Edited on 11-12-2011 by starman]
Chemistry- The journey from the end of physics to the beginning of life.(starman)
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Alastair
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others were minor things. But i will consider that one 
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Alastair
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And it didnt fail because of acid, i hope you understand that.
I have done that before.
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hissingnoise
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| Quote: | And it didnt fail because of acid, i hope you understand that.
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It failed because 'tempered' glass has a much higher C.O.T.E. than borosilicate glass!
Tempered glass is OK for heating water but sulphuric acid boils @ 337°C!
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Alastair
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But I was actually ''distilling'' water, right?
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Lambda-Eyde
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I think accidents like these could be avoided in 95% of cases if people stopped dicking around and bought some real labware instead. A beaker can be
had on eBay for a few dollars at most. Anyone can afford that, it's just a matter of priorities. Hobby chemistry doesn't have to involve using
thousands of dollars on apparatus, equipment and chemicals, but it doesn't have to, and shouldn't have to revolve around improvising
glassware. Using a few dollars on real glassware could save you an eye or your life...
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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Alastair
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Well i do have some glass, im just overly protective of it and i only use it when necessary. Just dont heat a nearly-empty vessel rapidly (yes it
cracked at a place that had no contact with the liquid and i have sucessfully done it with a little larger amounts and more steady heating)
I presume that was a special day when god of chemistry took vacation from helping me
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MagicJigPipe
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Hmmmm... Just don't use non-borosilicate glass for heating anything but pure water. Ever. I learned that lesson the hard way (it only took one
incident).
Trust me. That rule will never let you down.
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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jsc
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Glass fractures are going to occur, even with real pyrex.
Whenever you work with heat, assume a breakage. Whenever you work with pressure/vacuum assume an explosion.
What is important is your containment system, and since you weren't hurt and no damage was done, your containment system worked. So you succeeded,
good job.
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peach
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You'd be distilling up towards an azeotrope, which means the temperature will gradually rise from that of water towards that of azeotropic sulphuric
acid as the remaining liquid becomes more and more concentrated and approaches it's own BP.
Once the temperatures start getting up towards 300 and 400 with borosilicate, you do need to consider letting it cool gently again; e.g. switch the
heat off and leave it in place, as opposed to immediately removing or submerging it. It's hard to do with normal sized flasks and 200C, but
borosilicate certainly can shatter due to thermal shock alone as the heating & cooling rates & masses involved increase; more so if the
heating / cool is not uniformly applied. It's easier to shatter full glassware than it is empty, because there is can be a huge thermal mass on one
side of the glass and another at a greatly different temperature on the other.
Regular kitchen ware, I've managed to shatter that attempting to make cups of tea in tumblers when I couldn't find a cup.
[Edited on 23-12-2011 by peach]
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