Date: Tue Dec 4 17:26:09 2007

Author: Adam Beehler

Subject: Re: Cloud chamber

Bill Norwood wrote:

>1. Is there something strategic about the 90% alcohol, or is 90% just good
>2. We found that at dry ice temperature the isopropyl alcohol thickens while
>the methanol does not. And the thickening proved a nuisance for when we
>needed to move things around on the bottom of the chamber.
I just set up our lecture hall diffusion cloud chamber today and thus
re-read some of the literature that came with it. It states, "...and
soak with ethanol. DO NOT USE METHANOL OR ANY OTHER LIQUID....Alcohol
with a water content exceeding 30% will freeze on chamber bottom and
impede track observation." I have personally made cloud chambers that
worked just fine with ethyl alcohol and isopropyl alcohol (different
purities), and I have noticed that the purer the alcohol the better the
results but not always necessary. Alcohols with a higher water content
do indeed coagulate and/or freeze more. As to why not to use METHANOL,
I am not certain. One reason, for sure, is that it must do something
undesirable (either safety-wise, or equipment-wise); otherwise, the
company literature would not emphasize it so. But I can't think of a
reason why. My only guess is that the model I have can also be used
with a high voltage power supply (for a couple of reasons), and maybe
methanol is more prone to be dangerous.
Adam Beehler