Yes, I have had good success measuring the speed of sound in CO2. But
not with the method Anthony Lapinski described. It is more difficult
than you might imagine to get a column of pure CO2 gas, especially if
you intend to make measurements after gas generation ceases. The fact
that CO2 is heavier than air does not suffice to keep the CO2 where you
want it in pure enough form. It also takes a really long time to purge
out the air. I don't think you can purge the air even with a dozen
Alka-Seltzer tablets.
I am using a tube/plunger apparatus. Mine came from "pasco Scientific"
but it would be easy to make. I use a speaker/oscillator rather than
tuning fork because you need to keep monitoring the purging process. I
use an oscilloscope in XY mode to watch the Lissajou pattern between the
oscillator and a microphone pickup. I feed a steady flow of CO2 into
the side of the tube through a hole. My CO2 comes from a compressed-gas
tank.
This is way more complicated than Anthony would probably like, but it
points out the problem using CO2 (or other gases) in a tube that is in
the air. With the CO2 off, and air in the tube, you can establish a
Lissajou pattern on the oscilloscope screen. Then begin introducing the
CO2. The pattern on the screen changes, quickly at first, then more
slowly. You know you have the air purged when the Lissajou pattern no
longer changes. This takes waaaaay longer than you would imagine. With
a flow of perhaps 25 ml/sec it can take over a minute to get the air
purged. Then the flow can be backed-off to perhaps 10 ml/sec, but this
depends on the size of the tube and the size of leaks.
If you turn the gas off, the pattern begins to change immediately. That
is, without continuous CO2 flow to keep the air out, air gets in and
makes an observable difference "right now."
Although it was a nice idea, I don't see any way the Alka Seltzer will
work.
Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Bluffton University
Bluffton, OH 45817
(419)-358-3270
edmiston@bluffton.edu