Non-messy heat bath?

  • Thread starter bcrowell
  • Start date
  • #1
bcrowell
Staff Emeritus
Science Advisor
Insights Author
Gold Member
6,723
426
I teach physics at a community college, and I do a lab in which the students measure the pressure of air at constant volume, extrapolating to determine absolute zero. To get the best results (and also to make the lab more fun), I've worked on getting the widest possible range of temperatures. Currently we're using mineral oil for the hottest temp (smoke point of about 150 C) and an acetone/dry ice slurry for the coldest (about -20 C). The mineral oil has some disadvantages, however. It's messy, it isn't reusable, and if we don't dry out the glassware before heating it, we get spattering. Sometimes students are inattentive about the temp and it starts to smoke. I've been trying to figure out of there is some other solution that would be more convenient.

What might be nice would be some kind of soft, sealed, reusable thermal pack. Some of these are sold for use with food, others for medical use. They seem to contain cross-linked polymers. Handling them would probably be safer than handling the mineral oil. I'm not sure, however, how hot you can get these things. One brand is advertised as being autoclavable at 120 C, which isn't that hot. I'm also not sure if you could really mold them around the Erlenmeyer flask holding the air sample.

Another idea that's occurred to me is simply to put some canola oil in a ziplock bag and heat it in a microwave. The smoke point of canola oil is 225 C, which is quite a bit higher than the 150 C that I'm shooting for. In the worst case where the bag inflated and popped open during heating, we'd just get a mess inside the microwave.

Any suggestions? Thanks in advance!

-Ben
 

Answers and Replies

  • #2
Ygggdrasil
Science Advisor
Insights Author
Gold Member
2021 Award
3,511
4,183
Is it possible to use a simple sand bath (http://en.wikipedia.org/wiki/Sand_bath)?

I'm not sure heating canola oil in a ziplock is the best solution. I'm not so sure the ziplock be able to withstand the high temperatures and be secure enough to prevent spilling hot oil on your students.
 
  • #3
bcrowell
Staff Emeritus
Science Advisor
Insights Author
Gold Member
6,723
426
Aha! Thanks, Ygggdrasil, that's exactly the information I needed!

[EDIT] The only thing that occurs to me now is that I'm not sure how equalized the temperature of the sand would be. You probably can't stir it as well as you can stir a liquid.
 
  • #4
gravenewworld
1,105
25
Heating mantle?
 
  • #6
RocketSci5KN
162
4
Use a thermocouple within the air volume. Simplest way is to buy a 1/16" dia. SS probe type TC (say from Omega) and use a swagelok or similar fitting to handle the pressure. Some method of stirring the air within would be best, say a modified magnetic stirrer?
 

Suggested for: Non-messy heat bath?

  • Last Post
Replies
2
Views
12K
Replies
2
Views
1K
  • Last Post
Replies
2
Views
968
Replies
3
Views
533
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
1
Views
18K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
3
Views
1K
  • Last Post
Replies
4
Views
2K
  • Last Post
Replies
1
Views
2K
Top