It is not that nitrogen behaves any differently in maintaining tire pressures as oxygen does. At the pressures within the binoculars and even in airplane tires, Nitrogen, like Oxygen (Air is between 79 and 80% N2 and about 20% O2) behaves as an "Ideal Gas" and varies in volume inversly with the temp. and pressure (Boyle's law). When you start getting around 100 atmospheres of pressure, (3,300 feet of sea water) there is a slight difference in compressability and elasticity of different gasses... but at the range of pressures we are talking about, the gasses remain "ideal." Nitrogen has no significant advantage over Oxygen in the ability to maintain pressure. (Nitrogen has a gram atomic weight of 14, compared to 16 for Oxygen. But, changes in pressure effect rates of chemical reactions... AS pressure increases it favors a chemical reaction that will reduce the total number of molecules in the system.... or, simply said, it becomes more reactive. Nitrogen and hydrogen, for example, under pressure (remember air is 80% nitrogen) reacts to form Amonia; I don't know if there is enough dissociation in the water within the tire, for example to make this significant, perhaps our chemist can opine: N2 + 3H2 --heat/pressure--> 2NH3 SUMMARY" I think the reason they use N2 is that it may be the cheapest way to get rid of water... and, the less O2, the less reactive the mixture of gasses is, the better. Which may have been Phillip's summary as well.. but it would have nothing to do with the "size of the molecule." Phillip wrote: >I take the side of understanding that Nick Schade offers. The airline >industryuses nitrogen gas to maintain constant tire pressure. Being that >the molecules of nitrogen are larger they maintain that pressure whereas >air molecules being >smaller are able to permeate the rubber membrane or tire casing more readily. >Companies that transport (18-wheelers ) liquid Oxygen have their transport >tires filled with nitrogen for safety reasons (being that nitrogen is more >inert). *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
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