Aardwolf wrote:fosborn_ wrote:http://adsabs.harvard.edu/abs/2004JGRD..109.4309SAbstract
Permeation of various gases through elastomeric O-ring seals can have important effects on the integrity of atmospheric air samples collected in flasks and measured some time later. Depending on the materials and geometry of flasks and valves and on partial pressure differences between sample and surrounding air, the concentrations of different components of air can be significantly altered during storage. The influence of permeation is discussed for O2/N2, Ar/N2, CO2, δ13C in CO2, and water vapor.Results of sample storage tests for various flask and valve types and different storage conditions are presented and are compared with theoretical calculations. Effects of permeation can be reduced by maintaining short storage times and small partial pressure differences and by using a new valve design that buffers exchange of gases with surrounding air or by using less permeable materials (such as Kel-F) as sealing material. General awareness of possible permeation effects helps to achieve more reliable measurements of atmospheric composition with flask sampling techniques.
Them pesky water vapors acting all gaseous!
Adrwolfwrote...Yet again another paper that has no relevance. Why this has anything to do with the behaviour or the form of water in the air, who knows. In response, I don't see specifically why the water needs to be gaseous to pass the seal.The material is porous but I cant find any specifications down to what scale. Also, neither the glass nor the rubber surface can be manufactured down to flatness at the angstrom level, so it's likely sizeable droplets of liquid water could easily pass between them.
“” Aardwolf wrote:
Well I see no reason why if 1 molecule leaves, 2 or 4 or 6 couldn’t leave together whatever your mechanism. If fact I think it would be likely to be more because a single molecule needs to break 100% of its covalent bonds, while fighting gravity, whereas say a group of say 50 molecules would only be breaking about 50% of their covalent bonds. The larger the group the less bonds need to be broken therefore less energy is required to do it. And if there’s one thing I know for absolute certainty, nature doesn’t waste energy.
‘'
Well you are free to assume the glass and rubber is machined down to angstrom flatness and I'll assume it's not. I don't know how such a thing is even possible. How would they know if they succeeded? However, you are free to assume they achieve such serendipitous perfection. You are also free to assume that gas goes through the rubber but cannot escape at the seal if that's what you need to keep your point relevant.fosborn_ wrote:Aardwolf wrote:fosborn_ wrote:http://adsabs.harvard.edu/abs/2004JGRD..109.4309SAbstract
Permeation of various gases through elastomeric O-ring seals can have important effects on the integrity of atmospheric air samples collected in flasks and measured some time later. Depending on the materials and geometry of flasks and valves and on partial pressure differences between sample and surrounding air, the concentrations of different components of air can be significantly altered during storage. The influence of permeation is discussed for O2/N2, Ar/N2, CO2, δ13C in CO2, and water vapor.Results of sample storage tests for various flask and valve types and different storage conditions are presented and are compared with theoretical calculations. Effects of permeation can be reduced by maintaining short storage times and small partial pressure differences and by using a new valve design that buffers exchange of gases with surrounding air or by using less permeable materials (such as Kel-F) as sealing material. General awareness of possible permeation effects helps to achieve more reliable measurements of atmospheric composition with flask sampling techniques.
Them pesky water vapors acting all gaseous!Adrwolfwrote...Yet again another paper that has no relevance. Why this has anything to do with the behaviour or the form of water in the air, who knows. In response, I don't see specifically why the water needs to be gaseous to pass the seal.The material is porous but I cant find any specifications down to what scale. Also, neither the glass nor the rubber surface can be manufactured down to flatness at the angstrom level, so it's likely sizeable droplets of liquid water could easily pass between them.
\
Thinking about it, viscosity of a liquid compared to gas, comes to mind And the context of the paper is gas seals. And water vapor is an issue with gas seals in this paper, so vary relevant to this topic.
Your doubt is on the machining, is your assumptions.
Having a seal for a specific purpose that works and stating that seals are perfectly flat are very different things. However, I'm not sure if you are talking about metal welded seals here which is also very different to putting a stopper with an o-ring in a test tube.fosborn_ wrote:Clearly the machining isn't the issue, it s the seals concerning the useful shelf life of the samples. MY experienced with machine seals in hazardous locations is In environments where hydrogen sulfide gas eats electrical components , I have pulled machine covers, years after installation, with no corrosion at all. I have also worked on equipment at a same location with little protection and the electrical components falling apart form the same atmospheric environment. Also these work in explosive environments too. Vary critical. My life has depended on it on occasion.
As you say I don't think the analogy is relevant. Talcum powder has no molecular bonding so not really a test of the phenomena and also the particles are far too large where gravity is dominant.seasmith wrote:`“” Aardwolf wrote:
Well I see no reason why if 1 molecule leaves, 2 or 4 or 6 couldn’t leave together whatever your mechanism. If fact I think it would be likely to be more because a single molecule needs to break 100% of its covalent bonds, while fighting gravity, whereas say a group of say 50 molecules would only be breaking about 50% of their covalent bonds. The larger the group the less bonds need to be broken therefore less energy is required to do it. And if there’s one thing I know for absolute certainty, nature doesn’t waste energy.
‘'
Well science doesn’t yet have the means to observe the process directly, so we are both deep within the realm of conjecture here, but the above description somehow just doesn’t seem the most efficient option.
At a gross macro scale, if you blow gently on small mound of fine talcum powder it doesn’t fly up in chunks; rather it seems to lift off as individual particles and disperse evenly with the breeze. Perhaps it’s an irrelevant example there, but I don’t think, on an atomic level, that gravity is much of an issue;
and with water, “covalent” bonding is not always the dominant force.
Yes, I was going to point out that at the surface of any water in a pool etc. is not perfectly flat. What we see on the surface of a churning ocean is probably similar to what we would see at the sub-micro level of a pool. Either way the interaction needs to be stronger than gravity and it needs to be maintained. Air just doesn't have the energy to maintain the suspension of water droplets.seasmith wrote:Just suppose however, that the surface H2O molecules are not ‘bumped off’ by collisions or Brownian motion of the air; but that the warming, irregularly-shaped water molecules are instead snagged and pulled off by the very much larger relative charges of the oxygen and nitrogen molecules, one or two at a time.
Fosborn may disagree. He assumes o-ring seals and test tubes are perfect.seasmith wrote:We know there is no such thing as an absolutely smooth surface. Not above absolute zero anyway...
We can't see particles evaporating off liquid water, I don't see why ice isn't the same. I find it even less likely a single molecule could escape ice.seasmith wrote:One might also look at the ablation of ice. We don’t see a haze of ice crystals or ‘fog’ lifting off an ice cube in that process, although some vapor may be seen condensing from the humid air around it.
∞
Aardwolf wrote:seasmith wrote:`“” Aardwolf wrote:
Well I see no reason why if 1 molecule leaves, 2 or 4 or 6 couldn’t leave together whatever your mechanism. If fact I think it would be likely to be more because a single molecule needs to break 100% of its covalent bonds, while fighting gravity, whereas say a group of say 50 molecules would only be breaking about 50% of their covalent bonds. The larger the group the less bonds need to be broken therefore less energy is required to do it. And if there’s one thing I know for absolute certainty, nature doesn’t waste energy.
‘'
Well science doesn’t yet have the means to observe the process directly, so we are both deep within the realm of conjecture here, but the above description somehow just doesn’t seem the most efficient option.
At a gross macro scale, if you blow gently on small mound of fine talcum powder it doesn’t fly up in chunks; rather it seems to lift off as individual particles and disperse evenly with the breeze. Perhaps it’s an irrelevant example there, but I don’t think, on an atomic level, that gravity is much of an issue;
and with water, “covalent” bonding is not always the dominant force.
As you say I don't think the analogy is relevant. Talcum powder has no molecular bonding so not really a test of the phenomena and also the particles are far too large where gravity is dominant.
And yes I agree there are other forces but I would assume they are in similar effect on molecular and liquid water so should have no effect on the overall behaviour. Covalent bonding however is very different between the 2 states as I have indicated, and in that point alone more energy is required to separate. Which is also demonstrated by Feynman's experiment. The stronger the electric field the smaller the resulting particles.Yes, I was going to point out that at the surface of any water in a pool etc. is not perfectly flat. What we see on the surface of a churning ocean is probably similar to what we would see at the sub-micro level of a pool. Either way the interaction needs to be stronger than gravity and it needs to be maintained. Air just doesn't have the energy to maintain the suspension of water droplets.seasmith wrote:Just suppose however, that the surface H2O molecules are not ‘bumped off’ by collisions or Brownian motion of the air; but that the warming, irregularly-shaped water molecules are instead snagged and pulled off by the very much larger relative charges of the oxygen and nitrogen molecules, one or two at a time.
Aardwolf wrote:And yes I agree there are other forces but I would assume they are in similar effect on molecular and liquid water
But my whole point is that at the macro scale gravity is predominant and we're talking about a smaller scale where electromagnetic effects are predominant.seasmith wrote:The point of that Macro-Scale similitude with a fine powder was to recall the general mechanics of Dispersion.
Actually, I should have referred to hydrogen bonding in my previous post (although not entirely convinced of the differences...). Apologies if there was any confusion although it doesn't change my point about the energy requirements.seasmith wrote:Re the comment on "covalent" bonding, do you understand the mechanics of 'hydrogen bonding' ?
I wasn't referring to anything about Feynman's theories on weather. I only was pointing out the experiment, that can be performed by anyone, demonstrating the effect of electric fields on a water jet.seasmith wrote:Re the Feynman lectures, he was a truly brilliant instructor and mathematician, but still a shill for the then emerging QED / Particle model; and he wrote those college lectures before satellites even began to probe the ionospheres and higher atmospheres. Some caution should probably be exercised before swollowing his ramblings on weather.
It might be more helpful if you specify exactly what you are talking about. As far as I am concerned I've addressed all the points/questions aimed at me. I'm pretty sure I haven't received the same consideration.seasmith wrote:I've noticed looking over this thread that, like McGinn, you seem to just gloss over a lot of stuff that doesn't fit your chosen narrative.
cheers,
I'm out
Aardwolf wrote:seasmith wrote:The point of that Macro-Scale similitude with a fine powder was to recall the general mechanics of Dispersion.
But my whole point is that at the macro scale gravity is predominant and we're talking about a smaller scale where electromagnetic effects are predominant.
seasmith wrote:Re the comment on "covalent" bonding, do you understand the mechanics of 'hydrogen bonding' ?
Actually, I should have referred to hydrogen bonding in my previous post (although not entirely convinced of the differences...). Apologies if there was any confusion although it doesn't change my point about the energy requirements.
seasmith wrote:Re the Feynman lectures, he was a truly brilliant instructor and mathematician, but still a shill for the then emerging QED / Particle model; and he wrote those college lectures before satellites even began to probe the ionospheres and higher atmospheres. Some caution should probably be exercised before swollowing his ramblings on weather.
I wasn't referring to anything about Feynman's theories on weather. I only was pointing out the experiment, that can be performed by anyone, demonstrating the effect of electric fields on a water jet.seasmith wrote:I've noticed looking over this thread that, like McGinn, you seem to just gloss over a lot of stuff that doesn't fit your chosen narrative.
cheers,
I'm out
It might be more helpful if you specify exactly what you are talking about. As far as I am concerned I've addressed all the points/questions aimed at me. I'm pretty sure I haven't received the same consideration.
What exactly have I "glossed" over?
Postby jimmcginn »
H2O molecules can only be pulled off the surface of liquid water in clusters. Any attempt to pull them off individually or even in smaller clusters of 2 to 5 H2O molecules will be defeated by the fact that the breaking of H bonds activates polarity in associated H2O molecules.
It must be emphasized that no stable clustered unit or arrangement has ever been isolated or identified in pure bulk liquid water. A 2006 report suggests that a simple tetrahedral arrangement is the only long-range structure that persists at time scales of a picosecond or beyond.
http://www.chem1.com/acad/sci/aboutwater.html
by seasmith » Well science doesn’t yet have the means to observe the process directly, so we are both deep within the realm of conjecture here,
http://www.chem1.com/acad/sci/aboutwater.htmlA variety of techniques including infrared absorption, neutron scattering, and nuclear magnetic resonance have been used to probe the microscopic structure of water. The information garnered from these experiments and from theoretical calculations has led to the development of around twenty "models" that attempt to explain the structure and behavior of water. More recently, computer simulations of various kinds have been employed to explore how well these models are able to predict the observed physical properties of water.
This work has led to a gradual refinement of our views about the structure of liquid water, but it has not produced any definitive answer. There are several reasons for this, but the principal one is that the very concept of "structure" (and of water "clusters") depends on both the time frame and volume under consideration. Thus questions of the following kinds are still open:
How do you distinguish the members of a "cluster" from adjacent molecules that are not in that cluster?
Since individual hydrogen bonds are continually breaking and re-forming on a picosecond time scale, do water clusters have any meaningful existence over longer periods of time? In other words, clusters are transient, whereas "structure" implies a molecular arrangement that is more enduring. Can we then legitimately use the term "clusters" in describing the structure of water?
The possible locations of neighboring molecules around a given H2O are limited by energetic and geometric considerations, thus giving rise to a certain amount of "structure" within any small volume element. It is not clear, however, to what extent these structures interact as the size of the volume element is enlarged. And as mentioned above, to what extent are these structures maintained for periods longer than a few picoseconds?
Maol wrote:to measure the strong bond involving a hydrogen atom sandwiched between two oxygen atoms.
Maol wrote:to measure the strong bond involving a hydrogen atom sandwiched between two oxygen atoms.
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