While we're on Acrylamide....

Bryan L. Ford fordb at bcc.orst.edu
Mon Aug 3 21:01:12 EST 1998


Peter seems to have once again taken my measured and accurate response
as a personal affront to his chemical prowess.
 
Here is the original question from Beth:

> > > > Any of you chemistry-saavy types know what sort of nastiness one is
> exposedt
> > > > to from BURNING acrylamide? Say....when your gel box arcs and catches on
> > > > fire? Not that this has ever happened to me, of course (heh heh!)
 
Here is the portion of his response Peter chose to emphasize:

> > > An arc would not be sufficent to cause the acryilamide to burn because
> > > Arylamide is not flamable by nature.  But if you placed the gel in a bomb
> > > calorimeter and ignited it, you would find CO, CO2, and CN.

Here is the portion of my response Peter includes:

> > The original question says acrylamide, but of course most if not all of
> > a mature gel will be polyacrylamide. Even if polyacrylamide were
> > flammable, it would be very hard to openly ignite a polyacrylamide gel
> > containing 90 to 95% water. But, if we were really talking about the
> > monomer, then consider that the heating of unpolymerized acrylamide
> > solid to its melting point leads to rapid, and if the quantity involved
> > is larger, to explosive polymerization.

Peter, who has demonstrated some amazing reading ability here before, is
about to interpret the the wording for us:
 
> This is not what was asked. 

>Man are you just being wordy or what?

You *do* have some problems with words, I am sorry.

> As for what you are saying...What unadulterated garbage.

Unadulterated garbage in your mind. See numerous references to this
"garbage" widely available even in your highly vaunted MSDSs. Or, on the
Web, for example at
http://www.qrc.com/hhmi/science/labsafe/lcss/lcss7.htm). Or even on your
lab bench "rapid polymerization on melting" (for example in the
acrylamide monograph in the Merck Index). 

> since I have no
> intention of teaching you about reaction kinectics,

I am grateful for this small favor. Perhaps the world will be wiser as
well.

> Suffice to say that as
> a gas the molecules that will not polymerize faster than a liquid.

Unlike you, Peter, I don't pretend to know more than the references. But
then again I also don't interpret melting as boiling. And from our
preceding discussions on the subject of acrylamide I would wonder if you
have much of a grasp of the kinetic processes seen in acrylamide as it
melts. But let me guess from my meager chemical training that the
density of liquid acrylamide is only slightly less than that of the
solid. So that on melting the collisional frequency of acylamide
molecules and their orientational freedom would greatly increase. Added
to this, the available activation energy would certainly increase as one
raised temperature. So mechanistically the fact of explosive
polymerization of molten acrylamide is no great surprise. Once you have
combed your references and quizzed your old profs or chemistry pals you
will no doubt have something more meaningful to say on this subject as
on some previous occasions.
 
> > This is perhaps another argument
> > for using the, available and actually less costly, pre-prepared 40%
> > acrylamide/bis-acrylamide solutions, for example from Amresco-- (no
> > connection to me)-- and store in the fridge after opening. A lab fire is
> > bad enough without extra explosions.
> 
> More words with little said
>

Listen up, Peter! A number of individuals responding to this thread have
indicated that they are regularly using powdered (that is solid, for you
Peter) acrylamide. So the advice to use the solutions is relevant, it is
economically sound, and it is a reasonably charitable thing for one
scientist to suggest to another on safety grounds. What do you think
this newsgroup is for? Just a place where you, with your apparently poor
understanding of practical chemistry, can ridicule those who may not
have taken quite as much theoretical chemistry? If so, that seems to be
quite regularly backfiring on you, Peter.

> > The bomb calorimetry seems a bit incomplete here. CO (carbon monoxide,
> > often a fuel of industrial origin and use) will readily burn to CO2 in
> > the calorimeter. CN or C2N2 (cyanogen) "burns with a pink flame"
> > according to the Merck Index, the complete combustion products of which
> > I would guess to be CO2 again and one or another nitrogen oxide such as
> > NO or NO2.

In a moment of rare magnanimity Peter yields:

> Well I will admit that NO2 should be included but while we are at it, PNAs
> will be formed as well and the amount of each product formation will be
> dependant on the pressure and  the percent oxygen in the gas phase of the
> Bomb.

PNAs? I can think of a couple of definitions fitting this acronym. Let's
have the full wording Peter, or is the spelling too much?  We, the
readers, are used to doing the interpretive labor, so let us have your
interpretation of the full name.
 

> > If by chance the accidental burning of polyacrylamide led to the
> > evolution of CN or HCN then the questioner should be concerned. But a
> > good fire (supplying the oxygen and heat of activation) would likely
> > leave little free CN... cyanogen and oxygen produce one of the hottest
> > flames known-- well above oxyacetylene or oxyhydrogen torches in
> > temperature. Of course the toxicity of CN (similar to cyanide) keeps it
> > even from consideration as a practical flame, anyway these days there
> > are much better ways to heat stuff way hot!

> More words with little said.  Once again Bryon's mouth is moving right along.

More words (typed, the mouth is quite still, thanks) that completely
contradict any assumption that CN would not combust in a bomb
calorimeter. More words that answer part of the original question from
Beth.

But, of course, this is of "little" importance to Peter.

-Bryan

(Is that better, Susan Jane?)



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