Sciencemadness Discussion Board

cause of explosion

Cloner - 9-6-2011 at 07:03

I had a small explosion today in a heat degradation reaction. I was heating by flame about 10g of polylactic acid melt together with 1,4 g zinc powder and 0.3 g zinc chloride. There was a lot of gas formation in the test tube I used. I was collecting the gas distillate in a corked erlenmeyer with gas outlet. Fortunately I wasn't hit, although the fume hood was splattered with glass and the usual viscous, dark mess.

When the explosion occured, there was air intake into the heated test tube caused by a pause in heating (I needed to prevent foaming). The fragments of the blast indicate the top of the test tube exploded. There was quite some distance between the gas outlet of the collecting vessel and the flame and the test tube was corked and airtight.

I understand that hydrogen may form from the use of zinc powder. Also there is the formation of lactide, a semi high boiling organic compound I was intending to collect. Now I wonder what could be the cause of the explosion. I don't think it was the hydrogen itself, or the flame. Is it possible the metal particles caused the gases to react with oxygen?

The lactide molecule looks like this:

lactide.png - 7kB
Lactide

[Edited on 9-6-2011 by Cloner]

The WiZard is In - 9-6-2011 at 10:24

Quote: Originally posted by Cloner  
I had a small explosion today in a heat degradation reaction. I was heating by flame about 10g of polylactic acid melt together with 1,4 g zinc powder and 0.3 g zinc chloride. There was a lot of gas formation in the test tube I used. I was collecting the gas distillate in a corked erlenmeyer with gas outlet. Fortunately I wasn't hit, although the fume hood was splattered with glass and the usual viscous, dark mess.


Oooo Nooo You have recreated the Wolffenstein-Böters
Reaction, which has not been done since it was banned in 1405.
Nostradamus clearly predicts that the second time it is done
the End of All Time will soon follow!

It is time for the collective to get down of their bended knees
and pray before their periodic tables and ask too be saved.

You have been warned.

bbartlog - 9-6-2011 at 11:05

Well... hydrogen and oxygen seem like the most likely immediate cause of explosion. A wide range of ratios are explosive. So if your test tube had a bunch of hydrogen in it and some air entered via suckback, that would create the potential for what you describe. But the initiation is still a mystery, as the autoignition temperature of H2+O2 is actually rather high.

Cloner - 9-6-2011 at 13:59

Quote: Originally posted by The WiZard is In  

Oooo Nooo You have recreated the Wolffenstein-Böters
Reaction, which has not been done since it was banned in 1405.
You have been warned.


Wolffenstein clearly described a blackish compound in his 1405 publication but has not provided a quantitative analysis and a molecular formula. Therefor it is doubtful this is the same result.

Bot0nist - 9-6-2011 at 17:43

I was under the impression that the Wolffenstein-Böters reaction is an organic reaction converting benzene to picric acid by a mixture of aqueous nitric acid and mercury(II) nitrate. I thought Wizard Is In was just being cryptic.

Cloner - 9-6-2011 at 22:34

Too cryptic then because there is no apparent link to the reaction I describe.