Saturday, May 5, 2007

Liquid nitrogen ice cream

As a special treat for my General Chemistry students who had to put up with me 5 days a week plus a weekly lab for a full school year, I made liquid nitrogen ice cream for them on Friday.


I love doing this demo because it tastes so good.

Here is my recipe:

2 cups half and half
2 cups heavy whipping cream
1 cup sugar
a healthy splash of vanilla

The ingredients are mixed in a plastic bowl with a wooden spoon. Liquid nitrogen is added in small amounts until the entire mixture assumes a butter-like consistence. I serve it in 3 oz cups.

It tastes great and is loaded with fat. The creams are not light by any means. I've also made a chocolate version, but that is just too rich.

There is also the visually appealing part of making the ice cream.

Students ask a lot of questions about liquid nitrogen. Like: "where can I buy it?" and "does it hurt if it touches you?"

I like to tell the story of when I was reinstalling a cold trap full of liquid N2 on a schlenk line cold finger. Some liquid N2 boiled over and landed in the palm of my hand, I had the choice of dropping the dewar flask or sucking up the pain and finish tightening the clamp. I chose the later and ended up with a nice spot of frost bite on my palm.

2 comments:

Matt Jenks said...

Did you synthesize your own methyl vanillate?

That is pretty cool. My high school teacher always did all sorts of really cool demonstrations, and I blame her on helping turn me into what I am today (not the overweight and bearded would-be author part, either).

The coolest was when she taught how to make a battery out of a lemon, a penny and a nickel. I love any practical demonstration that ends in "and then you lick it"

Greg the Chemist said...

I really should try this some time.