Message-Id: <v01540b0aaf7171eef402@[192.174.2.173]>
Date: Wed, 9 Apr 1997 08:20:08 -0800
To: pinhole@exploratorium.edu
From: pauld@exploratorium.edu (Paul Doherty)
Subject: liquid nitrogen safety
Hi Dimitrios
Sorry I was out of town at the NSTA when your question came in.
Here are some comments to your questions.
Do other pinholers have additions?
(1) Is it safe to mix dry ice with liquid nitrogen?
yes.
(2) I once saw a person make frozen bubbles with liquid soap and liquid
nitrogen. Do you know the procedure for this?
Wow this sounds great! but it is new to me.
We make frozen bubbles by blowing them into an aquarium into which has been
placed a 5 pound block of CO2. As the bubbles cool and as CO2 diffuses into
them they slowly sink toward the block where they freeze and often burst
leaving behind a bubble fossil, or bubble shard.
(3) What is the best way to make fog using liquid nitrogen?
Just pour warm water into the liquid nitrogen.
(4) Is it safe to put boiling hot water into liquid nitrogen?
It should be. But I have never tried it. It will provide quite a thermal
shock to your container.
The main dangers of liquid nitrogen come from frostbite from contact over a
second or so. From liquid oxygen which condenses in the presence of liquid
nitrogen and is a potent oxidizer! And from inserting closed containers
containing air into the liquid notrogen (such as raquet balls) don't do
this. The air inside the ball liquifies and the ball hardens. You then have
a vacuum inside a brittle sphere. A dangerously implosive situation.
I hope all went well.
Paul Doherty