Text 5212, 108 rader
Skriven 2005-01-17 09:31:56 av Roy Witt (1:10/22)
   Kommentar till text 5187 av Robert Bashe (2:2448/44)
Ärende: Tire inflation
======================
Hello Robert.

16 Jan 05 21:37, you wrote to me:


 RB>> I guess I'm going to have to find that issue of C&EN to post the
 RB>> article here, since I shot off my mouth about it...

 RB> Here's what I found, for what it's worth. C&EN = Chemical and
 RB> Engineering News, the member publication of the American Chemical
 RB> Society.

A very interesting read, Bob.

 RB> Newscripts
 RB> C&EN
 RB> October 25,  2004
 RB> Volume 82, Number 43
 RB> p. 88

 RB> Pressure rising for nitrogen in tires

 RB> The idea that filling your car tires with pure, dry nitrogen is much
 RB> better for them than using plain old air is getting increased
 RB> attention.

Especially among the sports car racers here.

 RB> As pointed out by reader James R. Jeitler of North Idaho
 RB> College and others, tire outlets around the country are offering to
 RB> replace the air in your car tires with nitrogen for about $5.00 each.

Hmmm. I wonder how they get air out them?

 RB> There are a number of rather lofty claims being made about nitrogen
 RB> in tires. These include that pressure inside nitrogen-filled tires
 RB> does not rise or fall with temperature changes,

Wish he would have proved or disproved this one.

 RB> that nitrogen leaks out of tires much more slowly than air because
 RB> the molecules are bigger,

He disproved this one. Molucule sizes of air vs nitrogen = 1.2 vs 1.1

 RB> that nitrogen is an inert gas,

????

 RB> and that moisture and oxygen in air cause corrosion that shortens
 RB> tire life by 25 to 30%.

This is true. Which goes back to my question of removing the air.

 RB> Some credence to the idea seems to come from the use of nitrogen in
 RB> tires of race cars, jet aircraft, and some heavy trucks. Although
 RB> tire-pressure advantages are mentioned for these vehicles, another
 RB> reason cited here is that nitrogen will not contribute to combustion
 RB> in case of a fire around the tires, as the oxygen in air would.

A really crazy theory, as the fire is fed by oxygen in the air surrounding
it. If the tire were filled with sand, the tire would still burn.

 RB> Nitrogen generators are available for filling tires with the gas. At
 RB> least one company recommends using nitrogen that is at least 98% pure
 RB> in your tires to prevent rim corrosion and road failures. The
 RB> nitrogen is generated using a semipermeable membrane system that
 RB> allows oxygen, carbon dioxide, and water vapor to pass through,
 RB> concentrating the nitrogen. This concentrated nitrogen can then be
 RB> put into your tires.

This seems odd, since the size of the molucules of air are smaller than
those in nitrogen. How does this work?

 RB> Despite the claims of industry studies demonstrating that these
 RB> assertions are valid, much of what is promised seems to fly in the
 RB> face of logic. Reading the literature handed out by one nitrogen
 RB> promoter, Jeitler said, "I was interested to find out that nitrogen
 RB> no longer obeys the gas laws that we teach in general chemistry
 RB> classes, much less Graham's law of effusion."

 RB> Newscripts
 RB> C&EN
 RB> November 1,  2004
 RB> Volume 82, Number 44
 RB> p. 72
 RB> More on nitrogen

 RB> More readers are finding advertisements for using dry nitrogen gas to
 RB> fill auto tires in place of air (C&EN, Oct. 25, page 88). And the
 RB> concern about the rationale for this continues as well, particularly
 RB> the claim that nitrogen doesn't leak out of tires because it is
 RB> larger than oxygen. Physical chemist David Yang writes to point out
 RB> that the oxygen-oxygen double bond is about 1.2 Å long and the
 RB> nitrogen-nitrogen triple bond is about 1.1 Å. "They may have better
 RB> luck inflating with a really large molecule such as helium," Yang
 RB> jokes.

Someone here suggested that. Seems logical after reading this report.


 RB> -+- GoldED+/W32 1.1.5-0613
 RB>  + Origin: Jabberwocky System - 02363-56073 ISDN/V34 (2:2448/44)

Roy

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