This time it is a sealed tube reaction.
solvent is methanolic HCl (about 3-6 M, 10 ml). ace galssware 50 ml seal tube (max. 60 psi) with teflon cap.
temp is only 80-90 C. magnetic stirring.
after about 5 hr, somehow, the teflon cap was unscrewed (by itself !) and popped up to the ceiling of the fume hood along with all the solvents and reactants.
the reaction was not supposed to generate any gas.
the solution was green, which was not observed in a previous run.
the magnetic stir bar was broken after the explosion. magnetic metal inside can be seen.
Luckily, nobody get injured because of a protection shield we have.
Also nothing got broken. the seal tube is still intact and looks ok.
what is going on?
I guess the defective magnetic stir bar was the reason, which generated H2 gas in the presence of HCl. this is also explained why the color is green.
What is interesting is I still can not image how the tight teflon cap managed to unscrew itself.
In an early similar accident I had half a year ago, the sealed tube was just destroyed by the inside pressure.
Sunday, November 9, 2008
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3 comments:
I had a sealed tube incident last week too! The clamp I was using broke, and the tube fell into the oil bath. Fortunately, when I fished it out, the cap was still screwed on tightly.
A friend had a stir bar MELT about a year ago. Ever seen that happen?
Just find out telfon has a mp at about 300 C Celsius.
any temp above that, a GLASS covered stirring bar should be used.
ever seen that?
I used it once. a big problem of the glass stirring bar is that it is too fragile.
No, never seen one! I don't know of any reaction in our lab that's run at such a high temperature.
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