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Irwin and Rippe's intensive care medicine
carbon dioxide defuses through a latex balloon at a rate of approximately 0.5cc per minute
“mono-substituted halo-methane such as floromethane or bromomethane”
In their function as a contraceptive, condoms would have to be impermeable to spermatozoa, which are approximately 3000 nm in size. HSV-2 is considerably smaller than spermatozoa, at about 160 nm, and HIV is smaller still at 125 nm. Electron microscopy of male condoms shows an absence of full-thickness pores, but occasional pits secondary to imperfections in manufacturing. Permeability depends not just on the size of any pores in the latex barrier, but also variables such as the shape of the infectious agent, surface tension, temperature, pressure and pH of the environment
I think that none of us has a definite molecular-level understanding of the physical process occurring at closeoff, and it would be great if someone can do the experiments in the lab to understand that better. But it won't alter the empirical facts
A suspension of polystyrene 110 nm microspheres labeled with fluorescent dye served as the HIV-sized particle model in semen. They challenged each condom with this suspension for 30 minutes. The test did not include motion since stretching over the penis accounts for most pore stretching. Leakage of fluorescent dye occurred in 29 condoms (p .03). 21 condoms leaked at minimum leak rates 1 nl/s, 7 at 1-6 nl/s, and 1 at around 10 nl/s
industry officials admit condoms have holes 50 to 500 times the size of the HIV virus
I’ve found a puddle of vinegar outside the balloon but it is still not flat(that’s the balloons I meant not the vinegar or CO2). Its gone down overnight to 85mm. So what’s funny is that a lot of the vinegar got out but a lot of CO2 was still trapped inside
I’m still puzzled about why the vinegar leaked out but not much CO2 at first
I am confidant in concluding that CO2 leaks out of a typical bicycle tire more rapidly than air
the liquid would dissolve CO2 and act as a reservoir
Measuring the diameter of the balloon isn't the whole story; you need to know what's in it, and that's not always the same stuff that you start with
the paleoclimatologists and their models .. What they do not seem to consider is that it is the kinetic not collision diameter that is appropriate at this stage
atmospheric chemist/bike nut Alan Hills
Permeation by diffusion predicts gas leakage rates proportional to the inverse of the square root of their molecular weights. Using air as a reference the predicted leakage rates for common gases are: helium 2.7, air 1.0, nitrogen 1.02, oxygen 0.95, argon 0.85, carbon dioxide 0.81. It turns out however that the leakage rate of CO2 is huge, and the reason is that it is actually soluble in butyl rubber and is thus not constrained to normal permeation loss, it can transfer straight through the bulk rubber resulting in severe tire pressure loss on the order of a single day. .. A reference dealing with CO2 transfer through latex rubber sheds light on the loss process.
a theoretical chemist, with a particular interest in the development and application of simplistic model theories for chemical problems. My main area of interest is reaction kinetics, mechanism, and energy transfer in reactions.
The answer is that the carbon dioxide is much more "soluble" in the rubber that the balloons are made out of. For helium and oxygen, the chains of molecules in the balloon rubber repel the gas molecules, and they have to thread a maze, at best, to escape the balloon
thread a maze, at best, to escape the balloon
carbon dioxide is attracted to the chains of rubber molecules, and drawn in between them until it permeates the whole of the rubber. The rubber actually swells in the process. Once that has happened gas molecules can just as easily escape from either side of the balloon, and so the gas is lost relatively fast.
I think that none of us has a definite molecular-level understanding of the physical process occurring at closeoff, and it would be great if someone can do the experiments in the lab to understand that better
Bored chemist I couldn’t find anything about latex dissolving CO2 and mostly its the other way round so are you right about that or just guessing. One site says that the formula for pure latex is C3H3N so as you’re a chemist does that tell you anything about CO2 dissolving in it.
For many of the gases that make up the atmosphere there is little difference between collision and kinetic diameter, as seen in the listing below, but for CO2 this is not the case. Consequently, as the ice is compressed and pressure builds up in the pockets the CO2 molecules (and any smaller ones) escape from the pockets and move down the pressure gradient towards the surface, long after the larger gases like N2, O2, Ar and CH4 are trapped
if open microchannels are available -- the first or "Knudsen diffusion" option of the three mentioned in the pdf
Some of the pores will be so small that not all of the different types of gas molecules in the air mixture can pass, allowing only the smallest ones through, including CO2, but preventing N2, O2 and CH4. Other pores will be large enough for the whole air mixture to diffuse. I also hypothesise that both Fickian and Knudsen diffusion takes place, depending upon the size of those pores, with Fickian being relevant in the upper layers of firn and Knudsen at the approach to “complete” close-off and a gradual shift in emphasis down the ice sheet
is just plain wrong
All things dissolve in all other things to some extent (unless they react)
to make a solution of, as by mixing with a liquid; pass into solution: to dissolve salt in water
A homogeneous mixture of two or more substances, which may be solids, liquids, gases, or a combination of these
any combination of two different materials which don't react is a mixture, while solutions are a special kind of mixture where mixing occurs at the molecular level. Thus, all solutions are mixtures, but not all mixtures are solutions. To make the distinction clear, we'll use the phrase "physical mixture" to denote a mixture which is not a solution. So, by this definition, both muddy water and Kool-Aid® are mixtures of solid and liquid (that's how they're prepared), but only Kool-Aid is a solution
RD's suggestion will get upset by the CO2 dissolving in the water in the manometer
Pete Ridley was asking about the size of molecules and talked about collision diameter being the wrong one and kinetic diameter being the one to use so was he wrong about that?
A developing technology is membrane gas separation, which is more compact, energy efficient and possibly more economical than mature technologies, such as solvent absorption
whether or not that initial adsorption of CO2 in the snow is a chemical or a physical process (http://www.tutorvista.com/content/chemistry/chemistry-iv/surface-chemistry/absorption-types.php [nofollow]). My suspicion is that it is Chemisorption but as I’m not a chemist I’d appreciate your opinion. Following on from that is another question about adsorption in the deep firn, but that can be followed up later. Let’s work our way down the ice sheet looking at the different processes that Professor Zbiniew Jaworowski has been expressing concern about since 1992 and return to deep firn adsorption of CO2 and clathrate formation at a later stage
The accumulation of gases, liquids, or solutes on the surface of a solid or liquid
Hello Dr. Christie Ive had a first read of “Carbon Dioxide Separation through Polymeric Membrane Systems for Flue Gas Applications” ...sorry, you cannot view external links. To see them, please
REGISTER or LOGIN and was puzzled straight away by the start saying QuoteA developing technology is membrane gas separation, which is more compact, energy efficient and possibly more economical than mature technologies, such as solvent absorption Is a polymeric membrane like a latex balloon? If it is it seems to say that its not a solvent like water and the CO2 doesn’t dissolve in it so does it dissolve in latex?
Bored chemist you said that the formula for pure latex of C3H3NQuoteis just plain wrongso can you say what it really is?.
The rapid and random motion of tiny gas molecules results in effusion, the escape of gas molecules through very small openings
you’ve got it enclosed in a container. Its enclosed in a good balloon usually. Well the holes that it is escaping through may only be about the size of the atoms or molecules that are escaping so the helium can very gradually effuse through
the CO2 is .. dissolving in the latex .. effuses more quickly .. but then it is spontaneously released at the other side of the membrane
So diffusion refers to something moving through a matrix of some sort, and effusion refers to something moving out of a container
diffusion of dissolved air through the ice matrix into the bubbles
preferred diffusion of CO2 into the ice matrix
the gases .. can "dissolve" in the rubber, diffuse through it, and escape. Secondly the air outside a balloon full of CO2 will diffuse into the balloon .. so the balloon is filling up as well as emptying
The molecular sieve framework forms a well-defined repeating structure of regular channels and cages. Gas separation is dependent on the size of these channels and cages relative to the kinetic diameter of the gas. The difference in kinetic diameter of gas molecules (Table 1) dictates which molecular sieves are useful and provides an indication of selectivity . For example, Zeolite 3A separates hydrogen effectively from hydrocarbon feeds because the pore diameters are ~3 Å . Zeolite 4A has pore sizes of ~ 4 Å, which will separate carbon dioxide from nitrogen and methane
They are really the same process (or set of processes)
There are five possible mechanisms for membrane separation .. Knudson diffusion, molecular sieving, solution-diffusion separation, surface diffusion and capillary condensation .. Molecular sieving and solution diffusion are the main mechanisms for nearly all gas separating membranes. Knudson separation is based on gas molecules passing through membrane pores small enough to prevent bulk diffusion ..
'The permeation of small molecules through flawless polymer films occurs by the consecutive steps of solution of permeant in the polymer and diffusion of the dissolved permeant.' In the table for Natural rubber which follows (page III-233), the following permeabilities are given: oxygen 23.3, argon 22.8, nitrogen 9.43, carbon dioxide 153. Permeability is governed by solubility and diffusion. There is little difference in the respective diffusion coefficients: 1.73, 1.36, 1.17, and 1.25 for the four gases (note that diffusion coefficients through the polymer do not reflect either molecular size or molar mass directly). The striking difference in the permeability figure for carbon dioxide is associated with solubility in the rubber: heat of solution figures are -4.2 kJ/mol for oxygen, -0.1 for argon, +2.1 for nitrogen, but -12.5 for carbon dioxide
so does that mean that the hydrogen and carbon dioxide are dissolved into the membrane then diffuse through it and effuse out of it?
One may think of two possible pathways for the permeation of gas through ice, either through pores in a dry crystalline ice structure, or through a liquid phase which might exist in the ice. In the first case, according to Graham's law, one would expect that the smaller oxygen molecules would move through the ice in greater amount than the carbon dioxide molecules, but if permeation takes place through liquid pathways carbon dioxide would pass through in greater amount because of its 20 -30 times greater solubility. The latter was clearly the case, and this strongly suggests that we are dealing with permeation through a liquid phase
the smaller oxygen .. than the carbon dioxide molecules
Am I right thinking that the – “heat of solution” figures for O2 Ar and CO2 mean that heat is generated not used
I googled - permeability CO2 ice – and found a 1958 paper “Permeation of Gases through Ice” ...sorry, you cannot view external links. To see them, please
REGISTER or LOGIN that saidQuoteOne may think of two possible pathways for the permeation of gas through ice, either through pores in a dry crystalline ice structure, or through a liquid phase which might exist in the ice. In the first case, according to Graham's law, one would expect that the smaller oxygen molecules would move through the ice in greater amount than the carbon dioxide molecules, but if permeation takes place through liquid pathways carbon dioxide would pass through in greater amount because of its 20 -30 times greater solubility. The latter was clearly the case, and this strongly suggests that we are dealing with permeation through a liquid phaseI see that he saysQuotethe smaller oxygen .. than the carbon dioxide moleculesthen says that is why CO2 is more permeable because of liquid being there. If kinetic diameter should be used for the permeation would there need to be liquid for CO2 to permeate more easily and if liquid is there would the CO2 permeate even more easily and would it make more liquid because of “heat of solution” do you think?
If kinetic diameter should be used for the permeation would there need to be liquid for CO2 to permeate more easily and if liquid is there would the CO2 permeate even more easily and would it make more liquid because of “heat of solution” do you think?
Effusion is the word usually used to describe a gas escaping through a small hole- for example a pinhole in a piece of metal foil
calculate effusion rates directly from the kinetic theory of gases
but imagine that the bubble is an air pocket in an ice sheet approaching close-off, with all excepting one pore closed to all molecules (CO2 included). Imagine also that the hole size of that single pore is just larger than 0.33nm (the kinetic diameter of CO2) and that the red balls are CO2 molecules (N2, O2 and CH4 molecules present but not shown because they can’t escape but are still bouncing around inside in far larger quantities than CO2). Also imagine that the pore is not giving access to an empty space as shown but access to an equally small channel linking to another similar air pocket in a chain of such air pockets. Does that very simplified picture of the structure within the ice/firn help to clarify the basis of my main question? Does that very simplified picture of the structure within the firn/ice help to clarify the basis of my main question?
The key concept is a matter of homogeneous or heterogeneous. In a true solution, the component substances are divided at molecular level
Diffusion is the transfer of a material through the bulk of another material
diffusion refers to something moving through a matrix of some sort
Diffusion rates are measured empirically because they depend on a lot of odd parameters. The exception is the diffusion of one gas through another .. which you can calculate, and even that case is fairly complicated
I think that none of us has a definite molecular-level understanding of the physical process occurring at closeoff, and it would be great if someone can do the experiments in the lab to understand that better. But it won't alter the empirical facts[/quote http://www.thenakedscientists.com/forum/index.php?topic=38675.75 [nofollow].
Tried to post the following on the discussion forum, but the posting failed with an unspecified error, so I am sending it to you here
If my understanding is flawed again then please put me straight. If I understand correctly then can you explain the difference between a balloon that has been punctured with numerous tiny holes (let’s say 10nm diameter each) and one that naturally has numerous tiny pores (let's say 0.33nm) as a result of being blown up and the latex stretched? Michegan State University Chemistry Department provides a spacefill model (which you can zoom into) of the molecular structure of latex [urlhttp://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/lipidstr2.htm#rubber/url]. This tells me that there are tiny air spaces between the fabric (a matrix of C and H atoms? With no mention of anything else, like water) which must grow larger as the fabric is stretched (as in blowing up a balloon). At some stage the spaces must become large enough to let through any trapped gas inside, like He or CO2.
If the CO2 was going into the balloon like you said then the one with half CO2 should have gone down a bit by now
On 31/05/2011 10:21:16 I reported on my repeat of the balloon experiment that I started on 29th May where I had two balloons again, one filled with air and the other being half CO2 and half air. My comment after two days in which both balloons stayed the same size, was QuoteIf the CO2 was going into the balloon like you said then the one with half CO2 should have gone down a bit by now After 17 days the situation was no different and I was tempted to terminate it, guessing that the reason might be that the balloons were coloured (not natural as on previous tests) and perhaps the die/colouring reduced the size of pores in the latex or was preventing the CO2 dissolving.I was about to terminate the experiment because my wife had complained about the tape measure I’d stuck to the floor to get the balloon diameter when I noticed that the CO2 balloon looked a lot smaller than the other and sure enough it has suddenly started to deflate. It was down to 350mm and half an hour later it was at 300mm v the original 440mm while the air one is at 420mm v 450mm. I tested the CO2 balloon in waterwhen it was at 300mm and saw no bubbles escaping through any leak but an hour later it is down to 230mm but still no sign of a leak when immersed in water.Have any of the experts here any idea why there would be that delayed response and what is causing this sudden collapse? - Dr. Christie, please help.
Regarding Dr. Christie’s response of 14th June @ 19:13 it looks as though the preferential escape of CO2 v other atmospheric gases from a latex enclosure may be a different process to that covering the escape of CO2 from air pockets in ice. On the other hand, Dr. Zbiniew Jaworowski has discussed in several of his numerous papers how liquid water exists in deep ice. I propose to take a look at his ideas again and comment on them in the hopes of getting some further assistance here on that .
.. meltwater seeps down and collect over impermeable layers. The firn density gradually increases with depth and at .83 g/cm3, firn changes into solid ice in which all pores are occluded, forming the primary air bubbles. Between a depth of 900 to 1,200m air bubbles disappear. Liquid water is contained in quasi-infinite network of capillary veins and films between the ice crystals. ..
.. liquid water is present in ice even at very low temperatures, and because many chemical and physical processes occur, in situ, in ice sheets and in recovered ice cores. These factors, discussed in References 8, 12, 22, and 24-28, change the original composition of air entrapped in ice, making the ice core results unrepresentative of the original chemical composition of the ancient atmosphere ..
.. Some False Assumptions - For climatic interpretation of the ice core data the following assumptions are used:.. (2) No liquid phase occurs in firn and ice at average annual air temperatures of 224°C or less .. these assumptions are incorrect, and thus that the conclusions on low pre-industrial levels of atmospheric greenhouse gases are wrong .
I think that none of us has a definite molecular level understanding of the physical process occurring at close-off ..
Professor Eric Wolff said on Pete Ridley’s “Another Hickey Stick Illusion?” threadQuoteI think that none of us has a definite molecular level understanding of the physical process occurring at close-off ..(http://www.thenakedscientists.com/forum/index.php?topic=38675.msg354373#msg354373). If we can for the moment make the assumption that Jaworowski is correct about that water in firn (and there are plenty who say that he is wrong) what effect do you think that would have on the movement of CO2 within the firn and ice?
.. intrigued with the idea of a Hickey Stick ..
to miss the whole point of the evidence in the Vostok Ice core
.. can only move from regions of higher concentration to lower concentration ..
.. sharp variations over periods of less than 1 kyr in the Vostok record ..
.. The detail of presence of liquid water or not, or fancy notions about diffusion mechanisms and bubble formation mechanisms and so on ..
.. that there is 100% solid proof in the ice record that the CO2 has moved less than 1 kyr through the profile in the whole lifetime of the ice sheet ..
Dr. Hartmut Frank (Professor of Chemistry and Ecotoxicology, University of Bayreuth, Germany) who wrote the forward to Jaworowski’s 1994 paper, says QUOTE:.. Prof. Jaworowski's main argument is valid and will remain valid because it is based on simple, but hard physicochemical facts. Most of the facts can be found in the old, traditional "Gmelin's Handbook of Inorganic Chemistry” - but nobody reads such books anymore today. The facts are so basic that one cannot even start a research project on an investigation of the validity of such carbon dioxide analyses in ice cores because the referees would judge it too trivial. But if one would apply proper quality assurance/quality control principles, as they are common in most other areas of application of chemical-analytical methods (for instance in drug control or toxicology) the whole building of climate change would collapse because of the overlooked fault.And so one continues because there are so many living in or from this building. UNQUOTE
wouldn’t those persistentQuote.. sharp variations over periods of less than 1 kyr in the Vostok record ..still exist if the original CO2 concentration was much much higher than the level shown in the ice core record if the rate of migration was very very slow? Could not a slow rate of migration still leave residual peaks and troughs as seen from that record?
Under those circumstance could not the claim thatQuote.. that there is 100% solid proof in the ice record that the CO2 has moved less than 1 kyr through the profile in the whole lifetime of the ice sheet ..be more opinion than fact?
Of course, not being a scientist I could be totally wrong, but Jaworowski and his supporter Professor Hartmut Frank are scientists, the latter being highly regarded by his peers.