Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: Partial pressures



Sounds like sloppy language ... yea!

On Wed, 29 Mar 2000, Herbert H Gottlieb wrote:

Here is an interesting question that I just received from a colleague
concerning the breathing problems faced by scuba divers. The
errors concerning the causes of narcosis are obvious but what is
a better explanation of the phenomena?

In Science Links, vol. 14, page 45, there's a discussion of partial
pressures, some of which I'll quote here:

"Ordinary air is about 21 percent oxygen and 78 percent nitrogen. Under
water, each gas exerts its own pressure, independently of the other.
That means the compresed air that a diver breathes at 10 meters actually
has 42 percent of the total pressure due to oxygen alone. That's
I suspect the percent here means percent of the normal pressure at a
total pressure of one atmosphere.
The composition of the gas provided in % by mass or volume as you
choose is controlled by the supplier.
The concentration of dissolved components in solution is described by
Henry's law, which relates the partial pressures in pressure units, not
gas mass or volume fraction, to the concentration in solution.
If the concentration fractions in the gas remain the same and the
total pressure is doubled, the partial pressures also double as do the
concentrations in the solution (approximately).
-- Challenge broadens the vista of capability --

John N. Cooper, Chemistry
Bucknell University
Lewisburg PA 17837-2005
jcooper@bucknell.edu
http://www.facstaff.bucknell.edu/jcooper
VOX 570-577-3673 FAX 570-577-1739