Inge
I don't really go in for the corpuscular theory of light! For me, it is
electromagnetic radiation the same as radio waves, x-rays, visible light
etc. In actual fact, the ozone layer is quite a narrowband filter which
reduces the ultraviolet radiation by about 90%. It is all a question of
energy. It requires energy for the ultraviolet light to split the oxygen
molecules into monoatomic oxygen. The latter tend to do two things: they
recombine with each other back into oxygen molecules in an equilibrium
state and they bash an oxygen molecule to form an ozone molecule. These
may also absorb UV energy and split back into an oxygen molecule and a
monoatomic oxygen atom and the process is reiterative and stays more or
less in equilibrium for as long as the sun is radiating.
The problem arises if the radiation knocks a chlorine or a bromine atom
of an organic compound. This starts a chain reaction with the ozone
molecules converting them back to an oxygen molecule and stealing an
oxygen atom which is subsequently knocked off by further radiation to
repeat the process hundreds of thousands of times. This is an ultra
simplification of a complex series of chemical reactions.
Whereas scepticism about such matters is always desirable in order to
filter the wheat from the chaff, the chemistry of the ozone layer is
well known and scientifically proven. The generation of ozone in the
stratosphere has been known since the 19th century but it was not until
the 1920s that Dobson did his pioneering work in measuring the stability
and thickness of the layer using the instruments which he invented and
which are still used today. I believe the first ozone observatory was
established in Davos, Switzerland, in 1924 but many others, worldwide,
were implemented within a matter of months. His instrument operated by
simultaneously measuring the solar radiation in the visible spectrum and
in the narrowband of the UV spectrum simultaneously and calculating the
differential.
The first fears of ozone-depletion from man-made gases were expressed by
Crutzen who was worried by the effect of N2O from stratospheric aircraft
exhaust and by Molina and Rowland, who developed the CFC theory of
ozone-depletion, in the early 1970s. These were not confirmed
scientifically until 1988, although most atmospheric scientists
subscribed to these theories before then. They are not theories now, but
solid scientific fact. It is interesting that the Montreal Protocol was
signed in 1987, while it was still theoretical, on the basis of the
precautionary principle. And thank goodness for that! A couple of years
delay might have been very serious: and we're not out of the woods yet.
Although the rate of increase of ozone-depletion has dropped, we still
not have reached the peak and nor will we do so until about 2050. It is
unlikely that we will reach 1980 levels before the end of the century.
This is because of the atmospheric residence time of many of the
chemicals that are controlled substances under the protocol.
As for pyrolysing PFC molecules, the problem would be first of all
catching them, secondly ensuring total destruction which would require
incineration at about 1600° C for an hour or two (similar to destroying
other persistent molecules like chlorodioxins), and then knowing what to
do with the fluorine compounds such as carbonyl fluoride and
hydrofluoric acid, both extremely toxic and dangerous. This process
would cost a small fortune (compare with the cost of destroying the
Seveso residues!). Full marks for trying but not fully thought through!
Vacuum extraction of PFC vapours from soldered assemblies is only
partially successful for the reasons mentioned previously. In any case,
the vapours which are removed have to be captured and recycled, no easy
task! The perfect machine would have no need for replenishment of the
PFC compound during its lifetime. Any losses inevitably will be to the
air, sooner or later and generally, depending on throughput, we are
talking about a minimum of a kilogram or two per year. I would have to
recalculate it, but I seem to remember that 2 kg per year over 10 years
is equivalent to the carbon dioxide emitted by a medium-size car over
its lifetime (please don't quote me on this as I have not confirmed the
figures but it is something of this order, not forgetting that the PFC
will continue to have the same effect over thousands of years!).
Hope this helps!
Brian
Hernefjord Ingemar wrote:
> You are right, Louis.
> Aurora Borealis is seemingly a result of that kind of repulsion
> About UVA/UVB, how much is retarded by the O3, and what happens, are the photons reflected or absorbed or what happens? If you name the layer a filter, you might speak about a low/high/wide band pass filter. And filter efficiency.
> Inge
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Louis Hart
> Sent: måndag 2 februari 2009 15:20
> To: [log in to unmask]
> Subject: Re: [TN] Vapor Phase Soldering
>
> Inge, if my understanding is correct, ozone protects us from ultraviolet radiation, not cosmic radiation. The Earth's magnetic field deflects cosmic radiation from regions where people live.
>
> Incidentally, not long ago I read something about cosmic rays and theirenergies. I do not know what statistical distribution their energies follow, but one detected particle, an extreme case, had as much energy as a tennis ball as served.
>
> Louis Hart
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar
> Sent: Monday, February 02, 2009 3:23 AM
> To: [log in to unmask]
> Subject: Re: [TN] Vapor Phase Soldering
>
> sorry, I hit the 'send' before I was ready. Furthermore, I'm fascinatedby all the matters about the atmosphere. Obviously, our existence is much dependent of what happens up there. However, I don't use to accept everything without a little sceptical reflexion, and so is the case even here, namely, the famous ozone layer. All this investigation and writing andfear...are we sure about the role ozone plays, I mean, is the thickness,variation and existence of the ozone layer really that critical? Ozone alone can't be the only catcher of cosmic radiation, can it? How can this tiny layer of O3 molecules retard or even stop the enormous velocity of those space particles? Well, you can see how ignorant I am. But as such, Ialso am willing to learn.
> Thank you for taking you precious time to give answer.
>
> Inge
>
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