Cool stuff: The Ice-Calorimeter

From this week onwards, you will find yourself dealing with calorimeters during practicals, tutorials and lectures as we work through the topic of thermochemistry. You have handled the low-tech calorimeter made of styrofoam cups in the lab, and you have heard about a high-tech version called a bomb calorimeter. Have you wondered what the earliest calorimeters looked like and how they worked?


Here is a picture of the ice-calorimeter used by Antoine Lavoisier and Pierre-Simon Laplace to measure the enthalpy changes in 1785:

The chemists will place the reactants (the system) in the basket that you see in the middle of the calorimeter, and then pack ice (the surrounding) around the calorimeter. When the reactants react and produce heat, the ice around the calorimeter will melt. By measuring how much of the ice has melted, the chemists can then determine Q' and subsequently enthalpy change. However, as this deals with the melting of ice (change in state) instead of just an increase in temperature of water in the same state, the equations used to calculate Q' will be different. The Physics students should be able to figure this out.

Lavoisier and Laplace used this calorimeter to show that respiration (taking in oxygen to produce energy) is a form of slow combustion, or as Lavoisier put it "la respiration est donc une combustion". They achieved this by placing a guinea pig in the calorimeter and measuring the heat given out by the animal. The poor guinea pig. 

The calorimeter in the photo is currently housed in the Science Museum in London. If you ever have a chance to go there, be sure to check it out. While at it, you can inform the other tourists of the fascinating Chemistry behind it.