From: Henry Spencer <henry@zoo.toronto.edu>
Newsgroups: sci.space.tech
Subject: Re: Fluorinated oxidizers
Date: Sat, 22 Jun 1996 04:13:56 GMT

In article <4qaund$r68@hermes.is.co.za> franks@vironix.co.za (Frank Scrooby) writes:
>This may be a quick and stupid question BUT no one is seriously considering
>using flourine or flourides as a oxidizer? Right? Right? The stuff is almost
>impossible to handle. It will readily react with anything except a noble gas
>(and can even be convinced to form compounds with helium at exceptionally high
>tempretures).

Actually, fluorine will form compounds with xenon quite easily; the main
reason why it took so long for the noble-gas compounds to be discovered was
that the combination of the very high cost of xenon and the handling hassles
of fluorine severely hampered experimentation.

However, with many metals fluorine reacts just long enough to form a
fluoride film on the surface, after which it stops reacting, if you're
careful not to do anything to damage the fluoride film.  This is the basis
of industrial fluorine handling. 

Anyway, to address the original question...  Nobody is seriously
considering using fluorine for launchers -- given its handling problems,
fire risks, toxic exhaust, and very high cost -- but there is some
possibility that some of the nastier fluorine compounds, like ClF5, might
be used as oxidizers in specialized deep-space applications.  They offer
a large performance advantage over the more-conventional N2O4.

>...Your fuel tanks would have to be lined with
>the nickel cobalt (I think thats the alloy) compound which the petro-chemical
>industry makes their storage tanks out of. 

Actually, for fluorine (or ClF5), many metals will work.  Copper is quite
widely used.

>While the stuff might provide a really great head of thrust getting it to the
>rocket and keeping it safely long enough for the rocket to actually burn it
>seems to me to be an impossible task. Rather stick to plain aluminium tanks and
>LOX. At least its managable. 

SDIO successfully designed and tested a small hydrazine-ClF5 engine system,
which was tentatively slated to be used on Clementine 2 (back when there was
going to be a Clementine 2).  ClF5 is generally rather worse than elemental 
fluorine, as far as handling and corrosion problems go.
-- 
If we feared danger, mankind would never           |       Henry Spencer
go to space.                  --Ellison S. Onizuka |   henry@zoo.toronto.edu

From: Henry Spencer <henry@zoo.toronto.edu>
Newsgroups: sci.space.tech
Subject: Re: Fluorinated oxidizers
Date: Fri, 28 Jun 1996 14:17:18 GMT

In article <PGF9240.96Jun24214830@c30.ucs.usl.edu> pgf9240@ucs.usl.edu (Fraering Philip G) writes:
>> Well, you're quite wrong about fluorinated carbon compounds - they're
>> *stable*.  Got a Teflon frying pan?
>
>Could those be used as tank liners for fluorinated rocket fuels/oxidizers?

Not for the really aggressive ones, like F2 or ClF5.  Teflon is not
fluorinated all the way -- that would give you CF4 -- and it's still
vulnerable to fluorine attack.  Under the most benign conditions, with the
liquid just sitting there, Teflon will usually survive F2 or ClF5, but any
disturbance -- like having the liquid flowing past -- will usually result
in either ignition or slow quiet disappearance of the Teflon.

Fortunately, most of the fluorinated oxidizers don't actually need tank
liners, because if you give them a tank wall of a suitable metal, they
make their own lining of metal fluoride. 
-- 
If we feared danger, mankind would never           |       Henry Spencer
go to space.                  --Ellison S. Onizuka |   henry@zoo.toronto.edu

Newsgroups: sci.space.history,sci.space.policy
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Re: Black Horse (was: Re: HST as justification for STS)
Date: Wed, 30 Apr 1997 00:04:18 GMT

In article <335EB22D.167E@MIT.EDU>, Frank Johnson  <fjohnson@MIT.EDU> wrote:
>> The RL10 has actually been run on a very wide variety of things.  For
>> fuels, hydrogen, methane, and propane have all been used; for oxidizers,
>> they've fired it on LOX, liquid fluorine, and FLOX (LOX/fluorine mixture)...
>
>	Liquid flourine? My Lord! What is the plumbing made out of? I thought
>that the only material able to contain F was stainless steel, which is
>rather heavy for use on a rocket engine.

No, many metals are quite workable for fluorine service -- copper is often
used in commercial fluorine work, for example.  The metals themselves react
quite enthusiastically with fluorine, but the fluoride layer that forms on
their surface protects them quite well, provided you are careful not to
scrub or melt it off.

Actually, I think the RL10 *is* mostly stainless steel and suchlike --
rocket engines of that vintage tended to be.  I expect that some minor
parts, notably seals, needed replacing with more resistant materials.

>	Just out of curiosity, was thrust/ISP did they get using H/F?

Alas, I don't have numerical details.  It might not have been a lot
higher than LOX/LH2; the Isp advantage of fluorine is exaggerated.
--
Committees do harm merely by existing.             |       Henry Spencer
                           -- Freeman Dyson        |   henry@zoo.toronto.edu

Newsgroups: sci.space.history,sci.space.policy
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Re: Fluorine vs. LOX etc. (was: Black Horse)
Date: Wed, 30 Apr 1997 00:24:05 GMT

In article <335F37B2.7EE0@dlr.de>, George Ellis  <George.Ellis@dlr.de> wrote:
>> The RL10 has actually been run on a very wide variety of things.  For
>> fuels, hydrogen, methane, and propane have all been used; for oxidizers,
>> they've fired it on LOX, liquid fluorine, and FLOX (LOX/fluorine mixture).
>> Mixture ratio has been varied extremely widely, including successful tests
>> running severely oxidizer-rich...
>
>I've read about using fluorine in an engine several
>times. Apparently, this stuff has never been used
>operational. Does anybody have infomation (numbers)
>on what's gained by replacing LOX by or mixing LOX
>with Fluorine?

Fluorine is somewhat more energetic than LOX, and the LF2/LH2 combination
is a great deal denser than LOX/LH2 (partly because LF2 is very dense,
partly because you don't need nearly as much LH2), which makes for a
compact vehicle.  Oh yes, and fluorine is hypergolic with any fuel.  The
downside is that LF2 is a pain to handle, it's inherently expensive, the
exhaust is toxic, it doesn't work well with carbon-containing fuels, and
engine design is difficult.

The hope with LOX/fluorine mixtures was to combine some of the advantages
of fluorine with the easier handling of LOX.  In particular, 30% fluorine
70% LOX is compatible with most LOX hardware, but does perform better and
generally gives hypergolic ignition.  (Plus, the oxygen lets you burn
carbonaceous fuels.)  It's still somewhat expensive and the exhaust is
still toxic, and although the idea was investigated in depth in the 1950s,
it hasn't gone anywhere.

Generally, fluorine hasn't offered enough of a performance advantage to
pay for its disadvantages.  A contributing factor is that by and large we
are still using the handful of rocketry concepts which looked good in
about 1960, because there has been very little serious investigation of
alternatives since then.

>Actually, I'd be extremly interested in learning
>about the Isp, thrust, etc., as well as the advan-
>tages / disadvantages of the fuel / oxidizer combi-
>nations and mixture ratios Henry mentioned above.

Very briefly... Methane and propane are much denser than hydrogen, and
depending on the application, this might be important enough to compensate
for the rather lower Isp (slightly better than LOX/kerosene).  Oh, and
they're also quite a bit cheaper, and rather easier to handle.  You'd
also get higher thrust, other things being equal (which they might not be
if you used a slightly-modified hydrogen engine), because denser fuels
give lighter engine hardware.

Running oxidizer-rich gives some of the same advantages:  a denser fuel
combination and higher thrust.  It's potentially rather hard on the engine
hardware, however.
--
Committees do harm merely by existing.             |       Henry Spencer
                           -- Freeman Dyson        |   henry@zoo.toronto.edu

Newsgroups: sci.space.history,sci.space.policy
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Re: Fluorine vs. LOX etc. (was: Black Horse)
Date: Wed, 30 Apr 1997 00:27:24 GMT

In article <5jo4jd$g32@ds2.acs.ucalgary.ca>,
Kelly McDonald <ksmcdona@acs.ucalgary.ca> wrote:
>I read a book once, by a guy who developed rocket fuels during the
>50's and 60's...

Probably John Clark's "Ignition!".

>...He mentioned work on I do belive a fluorocarbon CF5 (i
>belive), that had even better performance compared to straight F2...

That's ClF5, chlorine pentafluoride -- no carbon involved.  Performance
isn't quite as good as straight F2, because that big heavy chlorine atom
comes along for the ride, but liquid F2 is a cryogenic fluid while ClF5 is
liquid at room temperature under slight pressure.

It actually is possible to use fluorocarbons as oxidizers -- there are
some very impressive igniter compounds which are mixtures of Teflon and
powdered metals -- but performance isn't high.
--
Committees do harm merely by existing.             |       Henry Spencer
                           -- Freeman Dyson        |   henry@zoo.toronto.edu

Date: Thu, 15 May 1997 13:38:16 -0700
From: Bruce Dunn <bdunn@cyberstore.ca>
Newsgroups: sci.space.history,sci.space.policy
Subject: Re: Fluorine engine testing

Kelly Parks wrote:

>         That does not sound right. I know there's a lot of enviromental/
> health hazard problems associated with flourine, but I've seen studies
> that claimed Isp's in the mid 700's, approaching the low end of solid-core
> nukes. Certainly more than a 5% increase!

Isps in the mid 700s are not even theoretically possible, let alone a
practical proposition. For reference values, theoretical Isps are often
calculated for a somewhat arbitrary "model" engine which has a chamber
pressure of 1000 psi (6.89 MPa) and has a nozzle which expands the
exhaust until the nozzle exit pressure is 1 atmosphere.  Under these
conditions, theoretical Isp is:

hydrogen/oxygen	                390
hydrogen/fluorine               409 (5.4% increase)
hydrogen/lithium/fluorine       432 (10.8 % increase)

Substituting fluorine for oxygen as an oxidizer only slightly raises the
Isp, but does wonders for the bulk density of the propellant
combination.  Adding lithium to the mix raises the Isp (the
lithium-fluorine reaction is extremely energetic), but actually lowers
the bulk density as the optimum mixture ratio requires a larger
proportion of hydrogen than does either hydrogen/oxygen, or
hydrogen/fluorine.

In practice, these combinations are most frequently used or proposed for
upper stage engines, where expansion ratios are much greater than for
the "model" engine.  Hydrogen oxygen engines with expansion ratios of
about 50:1 to 100:1 can run at delivered specific impulses in the region
of 450-460, and there have been proposals for upper stage engines with
huge expansion ratios (1000:1 or more) which might have Isps of up to
480 to 490.  Rocketdyne, working some decades ago with the hellish
combination of fluorine, hydrogen and the liquid metal lithium, have
achieved delivered specific impulses of 542 in an engine with a 40:1
expansion ratio.  This appears to be the record for a chemically powered
rocket engine.

--
Dr. Bruce Dunn
General Astronautics Canada, Vancouver B.C.
http://www.genastro.com/  | 800-577-1117  | 604-876-7640
Reliable, low-cost transportation to low Earth orbit and beyond

From: "Bruce P. Dunn" <bpdunn@home.com>
Newsgroups: sci.space.tech
Subject: Re: Hybrid engine proposal?
Date: Tue, 12 Jan 1999 16:40:04 GMT

I had indicated that in the Li F2 H2 system, the resulting LiF mainly
exited the engine as a gas.  Hiram Berry called me on this, indicating
that the LiF left the engine as a liquid or solid.

After some checking I see that Hiram is right.  I had not done the
calculations directly myself, but had mis-remembered the results
published in an old paper on the subject, which I had not read for some
years.

--
Dr. Bruce Dunn
General Astronautics Canada, Vancouver B.C.
http://www.genastro.com/  | 800-577-1117  | 604-876-7640
Reliable, low-cost transportation to low Earth orbit and beyond

From: henry@spsystems.net (Henry Spencer)
Newsgroups: sci.space.tech
Subject: Re: Hybrid engine proposal?
Date: Wed, 13 Jan 1999 02:11:59 GMT

In article <369BB7A3.4B8307F0@burningbridges.com>,
Hiram Berry  <burningb@burningbridges.com> wrote:
>> ...The walls are further protected
>> by having the injector designed to produce a layer of relatively cool gas
>> (in this case, hydrogen would be the clear choice) next to them.
>
>Thanks for the explanation. That's a brilliant concept-- You'd need a full
>blown 3D combustion/CFD code to design these chambers, though, wouldn't you?

Not really... provided you're willing to lose a few in development. :-)
This sort of "curtain cooling" has been routine for liquid rocket engines
pretty much since the start; few engines can do without it.  Getting the
details right by experiment can sometimes be a bit expensive, though. :-)

>> Hot oxygen is almost as corrosive as hot fluorine, but a wide variety of
>> engines deal with it just fine, with the same tactics.
>
>In general, I guess that's right, with this difference: some metals and
>SiC matrix composites can form semi-protective oxide films, but I don't
>think there are any refractory fluorides...

Indeed a problem, although most of the oxides aren't all that great at
rocket-engine temperatures either.  Having relatively cool gas near the
wall is very important... to the point where the most devastating effect
of the uglier kinds of combustion instability is that they disrupt curtain
cooling, which usually means the chamber wall fails within a fraction of a
second.  (People who deliberately provoke this sort of thing for testing
use special *very*-fast-acting shutoff valves to avoid losing engines.)

Mind you, cooling in general *is* usually especially crucial for fluorine
engines, because they run so hot.  Except that Li-F-H doesn't, because
it's got all that lovely hydrogen cooling it down!

Curtain cooling works just about as well with cool oxidizer as with cool
fuel, by the way.  Historically, fuel *has* been preferred, partly because
the most popular fuels have useful side benefits (kerosene decomposes and
deposits a soot layer, which has quite significant insulating effects;
hydrogen doesn't have to get very hot to reach substantial velocities, so
curtain cooling with it doesn't reduce performance much).
--
The good old days                   |  Henry Spencer   henry@spsystems.net
weren't.                            |      (aka henry@zoo.toronto.edu)

From: henry@spsystems.net (Henry Spencer)
Newsgroups: sci.space.science
Subject: Re: HF reaction get best delta-H?
Date: Sun, 18 Apr 1999 00:57:22 GMT

In article <3717E7F7.4901DFD5@vtacs.com>, Dan  <stevans@nospmvtacs.com> wrote:
>    Just curious what the best delta-H is that a chemical rocket could
>get.  I dont have my chem book handy, but I heard someone say once that
>a hydroflouric reaction would be most effective.

As has already been noted, delta-H is not the whole story.

For bipropellants, F2/H2 is about the best you can do.  However, you can
do better than that with tripropellant combinations.  F2/Li/H2 has a
*measured* Isp (with a long high-altitude nozzle) of 542s, the best ever
for chemical propellants.  O2/Be/H2 can theoretically match or beat that,
but the gap between theory and practice is much wider there, quite apart
from some ugly practical problems like highly toxic exhaust.

>Could this mixture be
>used on any future inter-planetary missions, at least as a thruster system?

There were a lot of ideas for using fluorine in the 1960s (including
converting the Saturn V's LOX to a LOX/F2 mixture in the first stage and
straight F2 in the upper stages), but none ever materialized.

At the rather higher chamber pressures now considered normal, fluorine has
little advantage over oxygen.  So its assorted disadvantages -- handling
and materials problems, toxic exhaust, and high cost -- have kept it out
of space applications.  (Another disadvantage that would be an issue for
large-scale use is limited supply:  filling one "fluorinated" Saturn V's
tanks would take the entire output of US fluorine production for more than
a year!  Of course, production would be expanded, but even so...)

A more likely oxidizer choice for some extremely demanding missions would
be one of the storable fluorine-based oxidizers, like ClF5.  With suitable
choice of fuel, they have near-fluorine performance (and, alas, handling
problems even worse than fluorine's) without the problems of cryogenic
storage in interplanetary cruise.
--
The good old days                   |  Henry Spencer   henry@spsystems.net
weren't.                            |      (aka henry@zoo.toronto.edu)

From: henry@spsystems.net (Henry Spencer)
Newsgroups: sci.space.tech
Subject: Re: Li-F-H (was Re: Stuff)
Date: Wed, 6 Oct 1999 02:49:22 GMT

In article <7tabhp$hu$1@nnrp1.deja.com>,  <cray74@hotmail.com> wrote:
>1) How hard is it to store liquid fluorine?

Great care is needed.  It will attack almost anything; it's hypergolic
with most fire-extinguishing agents, not to mention almost everything
else.  You can store it in tanks made of certain metals only because it
forms a fluoride film on the metal surface... and heaven help your rocket
if that film -- which is thin and not mechanically strong -- gets rubbed
or washed off, or if there's an impurity (like a weld defect) in the
metal.  There is no effective way of extinguishing a fluorine fire.

Oh, and of course any boiloff is highly poisonous, so the usual procedure
is to keep the LF2 below its boiling point using an LN2 heat exchanger.

>2) Is it beyond the pale to just store lithium as a
>   liquid? I don't recall its melting point being over
>   200C.

Its melting point is about 180degC.  Note, though, that liquid lithium is
hypergolic with air.  Also, it's a horrible corrosive, attacking most
metals and a wide range of other things.

There are no flexible materials, suitable for things like gaskets, which
will survive liquid lithium, so all joints must be welded.  (There aren't
many that will survive fluorine, for that matter; even Teflon will catch
fire or wash away if the situation is at all unfavorable.)

>3) Would it be preferable to store lithium as a solid
>   and melt it on demand? It seems like the fuel flow
>   might be easily interrupted.

For storage on Earth, keeping it solid and melting it on demand is the
obvious way to go.  Within a rocket, handling solids is clumsy and keeping
things liquid does make the hardware simpler.

>4) How expensive are lithium and fluorine in bulk?

I don't have numbers, but neither is a common element, and both are fairly
difficult to extract because they're so chemically active and so dangerous
to handle.  Not only are they pricey, but production capacity is limited:
Tischler once noted that using 30% LF2 in the S-IC would require nine
months of total US fluorine production per Saturn V launch.

>5) As a practical matter for a F-Li-H rocket, what sort
>   of environmental nightmare is this system? How badly
>   would environmental regulations hamper its use? Is it
>   no worse than the garbage spewed by the Shuttle SRB's?

It's not a disaster, because the fluorine pretty well all combines with
the lithium.  Lithium fluoride is poisonous but not spectacularly so
(although no fluoride is exactly healthy in more than trace amounts).
There'd be a trace of HF, I expect.  Considerably worse than the SRB
exhaust, I'd think, and environmental issues would be a problem.
--
The space program reminds me        |  Henry Spencer   henry@spsystems.net
of a government agency.  -Jim Baen  |      (aka henry@zoo.toronto.edu)

From: henry@spsystems.net (Henry Spencer)
Newsgroups: sci.space.tech
Subject: Re: Li-F-H (was Re: Stuff)
Date: Sat, 9 Oct 1999 23:31:11 GMT

In article <7tkp8j$r3m@odds.stat.purdue.edu>,
Herman Rubin <hrubin@stat.purdue.edu> wrote:
>>forms a fluoride film on the metal surface... and heaven help your rocket
>>if that film -- which is thin and not mechanically strong -- gets rubbed
>>or washed off...
>
>Very definitely so.  However, the present handling of
>fluorine uses the fact that this is relatively easy to
>accomplish for some common metals just by running fluorine
>gas through...  So if there is a part rubbed
>or washed off, the film will re-form.

Only if it's rubbed or washed off during handling operations with the
plumbing *empty*, so it gets a chance to re-form during the fluorine-gas
exposure which precedes the next filling.  If it gets rubbed or washed off
while the plumbing is full of liquid fluorine, e.g. by valve motion or
pump-seal rubbing, the result is a "take cover and let it burn itself out"
fire.

>>...Within a rocket, handling solids is clumsy and keeping
>>things liquid does make the hardware simpler.
>
>Why would it be necessary to have lithium as a liquid?
>Solid lithium would be hypergolic with fluorine.

Trouble is, lithium is not structurally strong in the first place, and
with its nice low melting point, it will quickly become even less so.  I
don't think solid lithium will hold together well enough in chamber
conditions for this to work.

>>There'd be a trace of HF, I expect.  Considerably worse than the SRB
>>exhaust, I'd think, and environmental issues would be a problem.
>
>HF is very bad for the environment.  It can etch glass, and
>it is used for this.  This will happen to any silicates,
>such as sand or most rocks or soil.

It's not like we don't have quite a bit of sand or rock around, though.
A much bigger problem, especially since this combination doesn't produce
*much* HF, is that fluorides in general are poisonous.  Both the LiF and
the products formed when the trace of HF hits sand (or whatever) are a
problem that way.
--
The space program reminds me        |  Henry Spencer   henry@spsystems.net
of a government agency.  -Jim Baen  |      (aka henry@zoo.toronto.edu)

From: henry@spsystems.net (Henry Spencer)
Newsgroups: sci.space.tech
Subject: Re: Li-F-H (was Re: Stuff)
Date: Sat, 9 Oct 1999 23:41:09 GMT

In article <7tjrlp$sf9$1@nnrp1.deja.com>,  <mockan@mailcity.com> wrote:
>> ...there is the immense size of the LH2 tanks required.  This is a
>> *performance* problem...
>------------------------------------------------
>OK. I'm confused. Wouldn't LH2 density and consequent tank mass be
>less of a problem with this tripropellant because unlike LOX/LH2
>combustion, the heat energy comes mostly from fluorine/lithium
>combustion, both relativily dense propellants? The added hydrogen
>increases Isp (and as you previously noted lowers temperature), but
>isn't the percentage used for the formulation noted that gave the
>Isp=542 (LF2-30%LH2/LLi) less, and not more, than the percentage
>that is typically used for LOX/LH2 engines?

Unfortunately, that number is *more* than a typical LOX/LH2 system uses,
indeed lots more.  70:30 is a 2.33 mixture ratio (pretending for the
moment that the Li/F2 is the "oxidizer").  Optimal LOX/LH2 mixture ratio
is about 4.0, but careful optimization for best vehicle performance --
considering the performance penalties of extra tank mass -- made even
Saturn-era LOX/LH2 systems run at about 5.0.  Modern ones have better
engines and tend to use 6.0 to reduce tank mass further.
--
The space program reminds me        |  Henry Spencer   henry@spsystems.net
of a government agency.  -Jim Baen  |      (aka henry@zoo.toronto.edu)

From: Bruce Dunn <bdunn@genastro.bc.ca>
Newsgroups: sci.space.tech
Subject: Re: Li-F-H (was Re: Stuff)
Date: Tue, 12 Oct 1999 15:46:26 GMT

Henry Spencer wrote:


>
> Trouble is, lithium is not structurally strong in the first place, and
> with its nice low melting point, it will quickly become even less so.  I
> don't think solid lithium will hold together well enough in chamber
> conditions for this to work.

Solid lithium can be introduced into a combustion chamber as a
suspension in a carrier liquid.  One trick is to use a "balanced density
slurry" in which the carrier liquid is the same density as the solid
particles.  If you get this right, the slurry has little or no tendency
to settle (the slurry however needs to be kept at a particular
temperature, as liquid densities change more than solid densities with
temperature).

If I remember correctly, solid lithium for chemistry use can be
purchased as a powder slurried in oil to protect the metal surface from
air.  The metal density is 0.534.  This density can be matched with a
mixture of propane and butane (with densities of 0.493 and 0.573 at 298
K respectively).  If the oil were replaced by a carefully formulated
propane/butane mix, the result would probably be a non-settling lithium
slurry with a viscocity dependant on particle size and metal loading
(investigation of the feasibility of this would make a nice student
project for some lab).

This fuel would not burn well with fluorine alone, as enough oxygen is
needed in the oxidizer to burn the carbon in the propane and butane to
at least carbon monoxide.  The best performance would be with FLOX (a
mix of liquid oxygen and liquid fluorine).  For a storeable system, ClF5
would work nicely as the principal fluorinating oxidizer, with oxygen
coming from a supplementary oxidizer such as FClO4 (perchloryl
fluoride).

I haven't explored the energetics of these systems to determine if they
are worth the trouble.  For storeable systems, one has to beat the
performance, propellant density and handling of N2H4 + ClF5, (or N2H4 +
N2F4), and for cryogenic systems, of H2 + O2 or H2 + F2.


--
Dr. Bruce Dunn
General Astronautics Canada, Vancouver B.C.
http://www.genastro.com/
Reliable, low-cost transportation to low Earth orbit and beyond

Newsgroups: sci.space.shuttle
From: henry@spsystems.net (Henry Spencer)
Subject: Re: Shuttle Atmosphere / Hypoxia
Date: Fri, 29 Dec 2000 16:15:37 GMT

In article <20001229081100.01135.00000642@ng-ch1.aol.com>,
Doug Goncz  <dgoncz@aol.comm> wrote:
>I flamed the Teflon insulation off of some small wires to prepare them for
>soldering deep in the chassis of the MOEPED. Yuk. I'd like to learn a little
>more about the smells of the halogens.

You won't be smelling raw fluorine; it's much too reactive, it wouldn't get
as far as your nose.  You'll be smelling more complex breakdown products of
Teflon... which is not a good idea, they're poisonous.

It is not clear what odor fluorine has.  A "distinctive musty odor" is
commonly associated with it, but this is also the smell of OF2, which is
one of the products when fluorine attacks water.  Given that the human
nose has water in it, it's not clear that it is physically possible to
smell fluorine.

And speaking of being poisonous, investigating the smells of the halogens
personally is not wise.  They're all seriously bad for you.  Early
fluorine chemists in particular had a notoriously short life expectancy,
but none of the halogens is anything you *want* to smell.

>...Does that sum up the "many steps" objection? In other words,
>there's usually at least one step and the energy available in the distribution
>must drive the components over that step.

Yep, and the nature and height of that step are difficult to predict
without detailed investigation of how the reaction proceeds.  Reactions
often proceed by several paths, relative rates change with temperature in
messy ways, and small impurities can lower the "hump" by catalytic effects.

>...with blood carrying
>oxygen, isn't hypo- -oxia the main condition to be worried about? I've seen a
>blood oxygen meter display approach 100 percent. It implies there's a limit,
>when every red blood cell has its cargo of oxygen to deliver.

Correct; in fact, a healthy person sitting quietly approaches that.  The
harmful effects of excess oxygen happen by more complicated means.
--
When failure is not an option, success  |  Henry Spencer   henry@spsystems.net
can get expensive.   -- Peter Stibrany  |      (aka henry@zoo.toronto.edu)