Radioactivity visible in cloud chamber

[Coda]

Hi,
We are working on the project makkng radioactivity visible in the cloud chamber. Can we use Isopropyl alcohol at 91% instead of 99%?
91% is available at drugstore
and time is tight for shipping...
Thanks!

[eedoherty]

Hi there,

From my understanding, as long as you can still get the 91% mixture to evaporate (you should see the mist on the inside of your Petri dish) with the heat of your hands, then it should work for this application. Based on the boiling point I found for 91% isopropanol I think that it would work just fine.

Hope that helps!

[eedoherty]

Also, while searching for information about the 91% isopropanol I found a tip that 99% is sometimes kept behind the counter at pharmacies! In case you are still interested in finding the 99%.

[AmyCowen]

There are two cloud chamber projects at Science Buddies. One of them does call for 91% and the other, which has a smaller chamber, uses 99%. My understanding from the scientist who authored the project is that the 99% was more effective for the procedure in that project, so if the project you are doing calls for the 99%, it is worth trying to get it. As Expert eedoherty notes... you may want to ask at the pharmacy to see if they have it behind the counter. (Links to Amazon sources are provided in the project as well.)

Amy
Science Buddies

[Coda]

Thank you so much! Greatly appreciated. We'll start with 91% as we got this already and if we can get our hands on the 99% we'll repeat.

[Coda]

Thanks for a very interesting project! Just a quick f/u:
A) 91% isopropyl alcohol worked for us and is easy to get.
B) Be sure to warm closed petri dish between gloved hands nicely with radioactive source leaning on the wall to saturate air inside with the evaporating alcohol and then chill it on the dry ice while looking for condensation tracks with flashlight. We put also isopropyl alcohol on construction paper.
C) Try different angles and positions of light vs observer
D) Exhaled air condensated onto outside of petri dish making it harder to see - saran wrap over dry ice under petri dish decreased that
E) We tested upright plastic strip and later felt across half of petri dish in area where clouds occurred and looked for block vs no block in other half of petri dish - nice comparison within petri dish of baseline as control and to be tested condition at same time.