Science Laboratory scenes in old files; whats the bubbling stuff int he beaker?

Question

Whats the bubbling stuff in those old Scienec Labratory scenes in old films? You know, that stuff thats sitting boiling away in the beaker off to the side?
What is it, and how do you make it?
(Not actualy boiling as in heat applied, its more of a foggy and bubbling stuff, kind of like BakingSoda+Vinigar)

Answer 1

I am guessing that the stuff that you have seen in old films is dry ice (CO2 in solid form) and when placed in a mixture of water and alcohol it will boil away even without heat. It would produce an fog and lots of photogenic bubbles. It can also be used to create a low lying fog like that seen in a lot of old 'horror' movies.

Answer 2

Dry ice in water, usually.