Environmentalists piss me off...

[Gurm]

Brian - and your sense of scale is escaping you. The amounts of CFC's present, combined with the size of the earth, and the distance to the stratosphere all conspire against this mixing.

And mixing doesn't work that way anyhow. Gases separate by weight. So do liquids. The longer you leave them, the more the separate. You have to stir pretty vigorously to mix them up, and there isn't that much stirring going on - wind isn't that vigorous compared to the overall distances we're talking about.

I for one would like to see an unbiased study showing actual CFC measurements in the stratosphere. Show me some former hairspray or R12 breaking down some ozone. Then show me the trail of hairspray and ozone leading from the hole to New York City.

- Gurm

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Listen up, you primitive screwheads! See this? This is my BOOMSTICK! Etc. etc.

[Brian R.]

Gurm - It really doesn't matter if you don't understand how it happens. CFC concentrations in the upper atmosphere are easily measured and they are known.

If you guys want a complaint, complain about the requirement that all cfc-propelled drugs must be replaced by non-cfc propelled ones.

This is a ridiculous issue, in my opinion and is causing a great deal of problems in the drug industry. The amount of cfcs used in propelled asthma medicine, for example is extremely small relative to all other uses. This is an exemption that should have been utilized in the Montreal Protocol, but wasn't. The problem with this issue is the HFA propellants are much less polar than cfcs and there are great problems with developing surfactants which are useful in these drugs.

Please stop arguing about a process which is well established and measured. I have given you the facts as I know them. There is no point in debating this further unless you want to cite the reference in the peer-reviewed literature with data to back up your claim that global ozone levels have remained constant over the past 100 years.

Edit - In addition, you're wrong, when mixed, gases do not separate because of density. If that were the case, the relative proportions of nitrogen and oxygen in the atmospere would vary with altitude. The oxygen would concentrate between the carbon dioxide at the earth's surface and the nitrogen in the upper atmosphere.

As you like to say: End of discussion

Anyway, UPS just delivered my G450 so I'm out of here.

[This message has been edited by Brian R. (edited 06 October 2000).]

[Rags]

Brian,

The wind will eventually cause all gases to be distributed around the globe at all altitudes. Gas mixing is driven by entropy.

You are correct to a point. The point being that this happens in the lower layers of the atmosphere, where gases have similar densities and are similarly affected by convection and currents. To get into the stratosphere, it just isn't happening to any great extent.

Density has nothing to do with it.

YOUR chemistry must be failing you. Density has A LOT to do with it.

Also, no matter what the rate of R-12 decomposition, eventually all R-12 will be converted to degradants and react with ozone.

I agree with this. Ozone occurs in more layers than you think. Ozone is most present in the lower layers of the earth, where the oxygen is in greater concentration (again, here we are with density again). Ozone is caused by quick hot flashes, such as sparks, lightning, electrical current, and even in volcanic activities. If R12 is going to combine with any ozone, it's going to be where the two compounds are in greatest concentration, and that is right here close to earth.

and the concentrations of both ozone and cfc degradants are well known.

They are actually unable to produce any hard statistics on how much CFC has made it into the ozone layer. There have been numerous studies, and ALL of them have been inconclusive. The environmentalists argue that the reason for now cfc's being measured are because they are already combined, and the byproduct has settled. BS!

Sorry - Your chemical intuition is failing you.

Chemical intuition has nothing to do with this thread

Take care,

Rags

[Gurm]

Brian,

I think Rags said most of it, but...

The atmosphere of the earth is NOT a uniform gaseous solution. (Is solution the correct word there?)

It has distinct layers. Within each layer, I agree 100% with your science. No problems whatsoever.

However, between layers VERY LITTLE MIXING OCCURS. This is well known.

And there is PLENTY of literature supporting the counterpoint to the "CFC's are making a great big hole in the ozone layer" theory. It just gets railroaded into a corner because it's not politically correct.

And, as Rags said - I have yet to see one single solitary CONCLUSIVE study showing CFC's in the upper atmosphere. Please, by all means find me one. And... make sure it wasn't sponsored by Al Gore, an environmental group, or someone else with a financial or political stake in the matter... hmm?

- Gurm

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Listen up, you primitive screwheads! See this? This is my BOOMSTICK! Etc. etc.

[Brian R.]

OK guys - Just to comprimise, I'll admit to less than scholarly knowledge of atmospheric science. I will not debate on what happens in the atmosphere further.

Properties of gases are what I know. No one can convince me that gases separate after mixing. It is not physically possible. Entropy never loses.

No Rags, my chemistry never fails me. I am a chemist.

[This message has been edited by Brian R. (edited 07 October 2000).]

[Rags]

Brian,

R12 does NOT mix with air. Entropy has NOTHING to do with this at all. Period. End of story.

Rags

[Brian R.]

I give up. I am not willing to spend the time to convince you.

[Gurm]

Brian,

Correct me if I'm wrong, but if you light a fire inside a bottle, the fire will soon go out due to lack of oxygen, right?

Cuz... um... the CO2 is heavier, and stays lower, and puts out the flame... cuz they don't mix, right?

Right?

- Gurm

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Listen up, you primitive screwheads! See this? This is my BOOMSTICK! Etc. etc.

[Brian R.]

"...if you light a fire inside a bottle, the fire will soon go out due to lack of oxygen, right?

Cuz... um... the CO2 is heavier, and stays lower, and puts out the flame... cuz they don't mix, right?"

No, the fire goes out because there the oxygen content in the bottle is too low to support combustion. The convection current set up by the flame will assure circulation of the gaseous contents and consume all the oxygen it can. Once the oxygen level falls below a few percent, it will no longer support combustion.

(All teh above is assuming you meant a closed bottle with sufficient fuel enclosed)

All gases mix perfectly evenly eventually throughout the entire volume of the container. The greater their density differences, the longer it will take without any stirring. Their intermolecular forces are not strong enough to overcome the entropy factor in minimizing the Gibbs free energy of the system. All systems come to equilibrium so as to minimize the Gibbs free energy. The evenly mixed gases have the lowest free energy, always. It is an equilibrium process and time has no meaning for this process. Any stirring speeds up this mixing.

It is true, as I said in one of the first posts, that you can get gases with different densities to layer by carefull pouring, but a fan will mix them very quickly. If no mixing is applied, eventually, the layering will become less distinct and over time the concentration of both gases anywhere in the bottle will be identical. This is a one-way process since it is downhill thermodynamically. The opposite can never happen spontaneously.

Another example of a downhill process driven by entropy is heating of brakes in a car. When you are driving and apply the brakes, the brakes get hot because the kinetic energy of the car's motion (organized, low entropy) is converted into heat energy (disorganized, high entropy owing to random molecular motion). This is a one-way process. It is extremely easy to create heat from the motion of a car because the overall energy of the system is lowered and this process is driven by the entropy term in the equation for Gibbs Free Energy. The process occuring in the opposite direction is extremely difficult. You cannot convert the heat energy of the brakes (random molecular motion, high entropy) into organized motion (car moving) without exerting a huge energy cost applied to the system.

My point is gases can be separated out of a mixture such as the air, but the energy cost in distilling them is high. They will never separate spontaneously.

[This message has been edited by Brian R. (edited 07 October 2000).]

[Gurm]

Brian,

Your argument kills itself.

Here's why:

If gases distribute uniformly, as you suggest, then why isn't there a HUGE concentration of ozone uniformly distributed throughout the atmosphere?

Why does Dallas have high ozone days but Boston doesn't?

Uniform distribution is bunk, utterly disproven simply by observation! I'm not arguing with the science of your case, I'm arguing with the results.

If your argument held for the earth's atmosphere, there would be 100% even distribution. There would also be big holes in the ozone EVERYWHERE, not just over Antarctica. These holes would be especially prevalent over large cities, volcanoes, and wherever the wind currents run.

But... they're not, are they? In fact there's only ONE hole. So from a uniform distribution we suddenly have all the CFC's on earth migrating magically to the south pole, then crossing into the stratosphere (something I seriously doubt can happen), then eating a hole in the ozone.

Nope, sorry. Doesn't fly.

Especially since, as you yourself admitted, your depiction of the atmosphere as a single unit is flawed.

The stratosphere contains a lot of Ozone, and almost no breathable oxygen. The ratios are completely different, the densities are different - it's a totally different unit.

To think that some magic force migrates heavy gases across from the lower atmosphere to the stratosphere is just ludicrous.

- Gurm

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Listen up, you primitive screwheads! See this? This is my BOOMSTICK! Etc. etc.

[Brian R.]

You've misunderstood what I was saying, I guess because I didn't explain myself well enough or describe the conditions in enough detail.

I said that over time, gases will tend to distribute uniformly. At equilibrium, they will be evenly distributed because this is the lowest energy configuration.

The atmosphere is not in equilibrium. It is, to a first approximation, in a steady state condition. Gases are being locally created and locally consumed and this process prevents equilibrium from being achieved. Under these conditions, gases are always (and must by thermodynamics) moving toward the lowest energy condition which is the conditions of greatest dilution. A gas cylinder of R12 opened in your front yard will have its contents diluted by the wind and the gas distributed and diluted more and more as time goes on. If you continue to open additional gas cylinders in your yard every day, the concentration of R12 in your yard may be the highest concentration of R12 in the world, but the R12 will not stay. It will difuse with the wind and eventually be distributed throughout the atmosphere.

In reality, classical thermodynamics is the universal driving force behind everything that happens in the universe. It is one of the few disciplines in chemistry (or physics) which is little studied anymore since it is so well understood and is totally predictable.

Please, I am not interested in teaching you gas theory and thermodynamic principles taught in freshmen chemistry. If you are unable to be convinced, that's fine. I have done my best, and I apologize for my shortcomings as a teacher.

[This message has been edited by Brian R. (edited 07 October 2000).]

[This message has been edited by Brian R. (edited 07 October 2000).]

[Gurm]

No no.

I _understand_ the concepts of thermodynamics. I even agree with your assessment (sp?) of what would happen in terms of mixing, etc.

What I DON'T agree with is that there is any plausible explanation for the observed effects, with regards to ozone depletion.

The ozone we're discussing is in the stratosphere and ionosphere. The CFC's are in the lower levels of the atmosphere. Now I 100% agree with you that if I open a bunch of R12 in my backyard it will be evenly distributed. However the amounts will be highest in my backyard.

Ok, fine. We're good so far, right?

Now, if these CFC's were reacting with ozone, the ozone they would MOST likely react with would be in my backyard, right? I mean they would react with SOME ozone elsewhere, but since the highest concentration is in my backyard, that's where they'd be most reactive, right?

Now look at a city like Dallas. Big pollution. Big CFC's. LOTS OF OZONE. MORE THAN ALMOST ANYWHERE ELSE.

Doesn't make sense, does it?

Now, where is the ozone hole the biggest? Over antarctica. By your arguments, the CFC's would disperse fairly evenly. Therefore the ozone layer would be thinning all over the world. Right?

Then why isn't it thinning over Dallas, but it IS thinning, or GONE, over Antarctica?

Now we still haven't addressed how the CFC's make their way into the stratosphere and ionosphere.

So let me sum up:

1. CFC's interact with ozone. Yes.
2. CFC's disperse evenly. Yes.
3. Ozone depletion is NOT occuring evenly. Yes.
4. Big hole in the ozone occurs in only one place on the globe. Yes.

Something doesn't add up, right?

- Gurm

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Listen up, you primitive screwheads! See this? This is my BOOMSTICK! Etc. etc.

[Brian R.]

One thing you are incorrect about. CFCs do not directly react with ozone. When they are exposed to high intensity sunlight, they degrade photochemically into very reactive species, some of which react with ozone. The sunlight intensity necessary is available only in the upper atmosphere and that is why the ozone depletion occurs there almost exclusively. CFCs do not decompose in the trophosphere (sp?). The sunlight is too weak. Probably 99.9% of the billions of pounds of CFCs free in the atmosphere are in the trophosphere. The remaining 0.1% or thousands of tons (my estimate) of CFCs have diffused into the stratosphere and can decompose into its degradants. I don't know the rate of photochemical decomposition of R12, for example, but it is known. You can measure this rate in any laboratory with a vacuum chamber, light source, and spectrophotometer.

As to how the CFCs make their way into the stratosphere, all I can say is that there is nothing stopping them. There may be a barrier owing to wind velocities or thermal conditions that retard macroscopic mixing of the trophosphere and stratosphere, but there is no barrier which stops or even hinders diffusion. Diffusion is the means by which R12 molecules are able to get into the upper atmosphere.

Diffusion is simply molecular motion due to thermal energy. The R12 molecules have RMS molecular speeds of 249 m/s at 25 C. This velocity is proportional to the square root of the absolute temperature, so it will be less than this in the upper atmosphere. This means the R12 molecules in the upper trophosphere are moving somewhere around 100 m/s (RMS) in every direction until they undergo a collision with another molecule. In rarefied atmosphere, these collisions occur less and less frequently, thus diffusion is more pronounced as a mixing phenomena than in the lower atmosphere.

The cities have the high ozone levels because it is created there and it takes the wind a while for it to disperse the ozone created. Since the creation of ozone is constant, the steady state concentration is higher there with the wind removing it at a fixed rate (at any particular time) and whatever producing it at a fixed rate.

Why Antactica? I haven't a clue. Maybe ozone doesn't like snow and ice?


[This message has been edited by Brian R. (edited 07 October 2000).]

[agallag]

I know how to solve this. You two just have to arm wrestle over it. Yeah, that's it...

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Andrew

I will not torment the emotionally frail

[Brian R.]

You are tormenting the emotionally frail