Definition of "CFC"?
Andrew C. Plotkin
labelled "Aero-Duster"; it sprays gas out of a long tube. (You use it to
blow dust out of hard-to-reach places in computers.)
On the front, in big letters, it says "CONTAINS NO CFC
CHLOROFLUOROCARBONS". This seems clear, if redundant; the company
(Miller-Stephenson, if anyone cares) desires to be ozone-friendly and is
advertising that fact.
Then, on the back panel, in small print, it says "Contents:
Chlorodifluoromethane." So what the heck? Is that not a
chlorofluorocarbon? Even if it's technically not, does it not have the
same potential to diffuse into the upper atmosphere and get broken down
into free chlorine and fluorine?
--Z
"And Aholibamah bare Jeush, and Jaalam, and Korah: these were the borogoves..."
Keith Warren Rickert
Chlorodifluoro methane is not, and it is termed a 'HCFC'.
These arent as long lived as CFC's and have less potential
to reach the stratosphere and release chlorine. (or so I am told)
Keith
David Blackburn
True, this is mainly because the H atom is reactive enough to do the molecule
in before it gets to the upper atmosphere. There are tables (sorry I don't
have a ref.) of relative ozone depleting potential, which is a combination of
lifetime and # of Cl atoms released into the ozone layer.
--
* Dave Blackburn dbla...@alleg.edu flames to se...@home.dev.null *
* Chemistry, Macs, Hypercard, cats, <>< religion, & the Dead *
* (Anyone else who held these opinions would be as crazy as I am.) *
* "Sometimes the songs that we hear are just songs of our own" *
Wim van Dorst
>On the front, in big letters, it says "CONTAINS NO CFC
>Then, on the back panel, in small print, it says "Contents:
>Chlorodifluoromethane." So what the heck? Is that not a
>chlorofluorocarbon?
The CFC nitpickingly spoken do not contain hydrogen. Those are the
HCFC (hydrogenchlorofluorocarbons). They have a much lower ozon depletion
potential, but still are (well may be) hazardous to the environment. The
most environmentfriendly are the HFC (hydrogenfluoro carbons) which do not
contain any chlorine at all, and thus have no ozone depletion potential.
The chlorodifluoromethane (often referred to as R22) is a HCFC, and at
present generally thought to be _the_ replacer for R11 and R12, which
were used up to now for CFC applications. As R22 still has an ozone
depletion potential of 0.22 (versus 1.00 for R11 and R12) is is considered
to be a temporary solution only.
>Even if it's technically not, does it not have the
>same potential to diffuse into the upper atmosphere and get broken down
>into free chlorine and fluorine?
No. See the above.
Met vriendelijke groeten, Wim `Blue Baron' van Dorst
Ole W Saastad
>The CFC nitpickingly spoken do not contain hydrogen. Those are the
>HCFC (hydrogenchlorofluorocarbons). They have a much lower ozon depletion
>potential, but still are (well may be) hazardous to the environment. The
>most environmentfriendly are the HFC (hydrogenfluoro carbons) which do not
>contain any chlorine at all, and thus have no ozone depletion potential.
But the HFCs are bad greenhouse gases. Look at the IR spectra of these
molecules, and you will see. CF4 should be perfectly safe, but it is a
potent greenhouse gas. Just like the C2F6 gas from Al production.
So none of these molecules are friendly ! They are usefull and nice to use
but all of them have side effects !
>Met vriendelijke groeten, Wim `Blue Baron' van Dorst
--
Ole W Saastad "Fat trout trailer park"
Dept. of Chemistry University of Oslo Norway.
Now at University of Colorado at Boulder / CIRES , Atmospheric Chemistry.