From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.chem
Subject: Re: CO2 Reaction Question
Date: 22 Mar 1996 07:45:26 GMT

In article <4it1nc$e2j@newsbf02.news.aol.com>, brianburt@aol.com
(BrianBurt) says:

>I desperately need the expertise of someone well versed in chemistry to
>answer the following question!
>
>I am starting work on a science fiction novel in which I need a very
>specific type of (hypothetical) chemical reaction to satisfy some central
>requirements of the plot.  Carbon dioxide and seawater need to be two of
>the reactants, and the reaction must:  A) be highly exothermic (the more
>violent, the better); and/or B) generate toxic product(s) (the more
>lethal, the better).  I have been using as a working premise some type of
>"mysterious" organometallic reactant/catalyst that, combined with CO2 and
>seawater, yields a carbonate (possibly calcium carbonate?) and explosive
>quantities of waste heat... but I'm not a chemist, and I don't know if
>this type of reaction is realistic or a candidate for satisfying my plot
>requirements.
>
>Any advice, guidance, or suggestions anyone out there can provide would be
>gratefully accepted and much appreciated.  (I promise to give proper
>credit in the book's acknowledgements.)  Thank you in advance for any
>input you can offer!

Why not?

Here's one that at least allows the suspension of disbelief.

Aluminum is added to many explosives because it reacts in such a
way as if it gobbled up the water either present in or produced by
the explosion. Some of these explosives are actually water solutions
of such things as ammonium, calcium or sodium nitrate or even the
odd perchlorate. Although  nobody knows exactly why, the 
hypothetically quite reactive mixture of aluminum and water does
not react explosively when smacked with a blasting cap or primer
unless an unspecified amount of oxidizer is added.

You can be pretty certain nobody has ever tried CO2/Water/Aluminum
powder at high concentrations of CO2 (High pressure). Since CO2
is liquifiable under pressure you can use pressure to create any
mixture of CO2/water you wish. If you say that that mixed liquid,
combined with aluminum powder, will detonate or at least explode 
under confinement, nobody can prove you wrong. You can even 
speculate that the carbonic acid present from the reaction of CO2
with water cleans the oxide film off the aluminum and sensitizes it.

If the creative license bothers you, just add some oxidizer to 
the brew, in the form of, say, ammonium nitrate and you've got
the first metallized explosive soda "POP" blasting agent.

Jerry (Ico)

Subject: Re: CO2 Reaction Question
From: candela@Glue.umd.edu (Philip Candela) 
Date: Mar 24 1996
Newsgroups: sci.chem

Alan \"Uncle Al\" Schwartz (uncleal0@ix.netcom.com) wrote:

: KEWL!  Use carbonic anhydrase as the catalyst.  It won't hold techncial 
: water, but it will scare the dickens out of the hoi polloi.  Oceans at 
: depth are saturated with CO2.

Just a note on that, Al: The oceans do have a high P(CO2) at depth but
geochemical studies, I believe, show only a narrow (in depth) zone
somewhere around 500 m that has values that indicate gas saturation (e.g. 
sum of all partial pressures of gases equal to total pressure, within
error). Once you dip below this zone, the combination of increasing
pressure and decreasing temperature an other bulk compositional and
dynamical factors decrease the partial pressure of CO2 in seawater FAR
below total pressure. 

With regard to some other comments on this thread: note: liquification of
CO2 at pressure does not ensure mutual solubility -over a range of T's and
P's there is a considerable field of liquid immiscibility betweem liquid
CO2 and liquid Water.  the addition of NaCl to this system can extend the
immiscibility to many hundreds of degrees(C) and a few kilobars (Deep 
ocean water at 6.7 km is at a pressure of about 670 bars).  In fact 
natural inclusions of fluid in quartz crystals at room temperature can 
contain vapor+liquid CO2 +liquid H2O  (the quartz xl acts as a pressure 
vessel - the total mechanical pressure in such inclusions can be high)

Phil Candela
Geologist
Univ of Maryland
College Park
candela@geol.umd.edu
http://www.geol.umd.edu

From: candela@Glue.umd.edu (Philip Candela)
Newsgroups: sci.chem
Subject: Re: CO2 Reaction Question
Date: 26 Mar 1996 09:16:13 GMT

Hi folks:
	My apologies to what is really a light-hearted, and interesting 
thread, but I must digress:

Gerald L. Hurst (glhurst@onr.com) wrote:

: In article <4j29ct$1lk@mojo.eng.umd.edu>, candela@Glue.umd.edu
: (Philip Candela) says:
:
: >With regard to some other comments on this thread: note: liquification of
: >CO2 at pressure does not ensure mutual solubility -over a range of T's and
: >P's there is a considerable field of liquid immiscibility betweem liquid
: >CO2 and liquid Water.  the addition of NaCl to this system can extend the
: >immiscibility to many hundreds of degrees(C) and a few kilobars (Deep 
: >ocean water at 6.7 km is at a pressure of about 670 bars).  In fact 
: >natural inclusions of fluid in quartz crystals at room temperature can 
: >contain vapor+liquid CO2 +liquid H2O  (the quartz xl acts as a pressure 
: >vessel - the total mechanical pressure in such inclusions can be high)
:
: I have a little trouble with your data. According to my references,
: the critical temperature and pressure of CO2 are respectively
: 31 C and 72.85 atm, which, if correct, means there is no liquid
: phase of CO2 above 31 C and therefore no immiscible liquid phase
: "at many hundreds of degrees (C)..." At lower temperatures I would 
: expect high pressure to drive the equilibrium to the carbonic acid 
: side.
:
: There are a lot of chemists working on liquid CO2 systems these
: days, so someone is sure to straighten us out.

: Jerry (Ico) 

Jerry -

 No, this needs no straightening out! :*) Let me explain. The liquid CO2-rich
phase that would coexist with an aqueous phase will, by virtue of
chemical equilibrium, contain dissolved water.  Therefore, the critical
point of CO2 (which is relevant ONLY to pure CO2), is not important. In
the binary system CO2 - H2O, as in any system of two "volatile
components", there exists a critical curve.  For each unique mole fraction
of CO2 in this binary system, there is a unique critical point (the locus
of these points is indeed the critical curve itself). The phase equilibria
of such systems is discussed in the elementary chapters of the classic
book by Ricci, "The Phase Rule and heterogeneous equilibrium". 

	The Critical curve in the CO2 - H2O system is highly non-linear
(sorry, but I do not have the classic reference in front of me - If anyone
out there is interested, e-mail me, and I will send you the citation).
Three component systems are, of course, more complex.  As I am writing at
about 3 AM, I do not have all the references for this system with me either, 
but a decade+ old reference on CO2 - H2O - NaCl phase equilibria is: 

Bowers and Helgeson (1983) Calculation of the thermodynamic and 
geochemical consequences of non-ideal mixing in the system H2O - CO2 - 
NaCl on phase relations in geological systems: Equation of state for H2O 
-CO2 - NaCl fluids at high pressures and temperatures.  Geochimica 
Cosmochimica Acta vol. 47, p. 1247 - 1275.  

Their thermodynamic analysis is based on high-quality phase equilibrium 
data by Franck and coworkers, and others, cited in the above reference.

With regard to NaCl - H2O, liquid - vapor equilibrium can occur in excess
of 800C and 1000 bars (the conditions underwhich I and my research group
perform experiments routinely within this, and more complex systems).  Of
course, to stabilize the liquid phase, the concentration of dissolved
salts must increase.  Although the critical point of pure water is at
about 221 bars and 374C, the critical point for 10 wt% NaCl in H2O is at
about 520 bars and 475C. The critical curve obviously extends from the
critical point of water to the critical point of NaCl; the maximum on this
critical curve, not examined experimentally, is estimated by some to be 
around 2000C and 2500 bars. The three phase equilibrium

{solid NaCl - NaCl saturated liquid - vapor}, 

that is, a boiling liquid saturated with NaCl solid (halite to us 
geologists) has a vapor pressure of about 390 bars at about 600C.
The phase equilibria in this system have been known for decades.  See 
Pitzer, 1984, J. Phys. Chem. vol 88, p 2689 - 2697, and Sourirajan and 
Kennedy, 1962, American Journal of Science, vol 260, pg. 115 - 141.

I hope this clears things up.  Again, my apologies for turning an 
interesting question re: "novels" into a lecture on physical chemistry.

Any comments welcome.

Phil Candela
Geologist
Univ. of Maryland
College Park
candela@geol.umd.edu
http://www.geol.umd.edu