The new version is available on-line from the FAA website,
it was re-written just a few years ago.

I was taught that the "air" is basically a uniform mixture
from seal level to outer space, with some variation for
local conditions. There is more water vapor over the ocean
than a large land mass, there is more dust below 10,000
feet. There is more ozone at 40-50 km because that is where
it is made. There is more man-made stuff below 18,000 feet
because we make it at the surface and the different layers
don't mix well. Volcanoes and thunderstorms transport stuff
to high altitudes.

Link http://www.faa.gov/pilots/training/handbook/


--
James H. Macklin
ATP,CFI,A&P

"Bob Gardner" wrote in message
...
|I have a book titled "The Atmosphere" (duh) and it breaks
the constituents
| down as you have noted. Nothing about change in
composition with altitude.
| How long has it been since the PHAK was rewritten, if
ever? I remember using
| it back in the 60s.
|
| Bob Gardner
|
| "karl gruber" wrote in message
| ...
| The PHAK (A US governmet publication, so it can't be
wrong!!!) pg. 2-1
| states:
|
|
http://www.faa.gov/library/manuals/a...ilot_handbook/
|
| The atmosphere is composed of 78 percent nitrogen, 21
| percent oxygen, and 1 percent other gases, such as
| argon or helium. As some of these elements are heavier
| than others, there is a natural tendency of these
heavier
| elements, such as oxygen, to settle to the surface of
the
| earth, while the lighter elements are lifted up to the
| region of higher altitude. This explains why most of the
| oxygen is contained below 35,000 feet altitude.
|
| Is this correct??
|
| I always thought that only the density changes until a
very high altitude.
|
| Best,
| Karl
| "Curator" N185KG
|
|
|
|