I then placed the thermometer probe into the water in the calorimeter and began taking temperatures in order to have an initial water temperature. That value was 21.1^oC. Once I had one temperature I inserted the test tube into the larger hole in the calorimeter lid and began to stir the solids vigorously with the paddle.

Because it is not possible to use a magnetic stirring bar in this set-up, it is important to occasionally mix the water in the calorimeter by swirling in order to insure thermal equilibrium. The entire reaction part of the experiment only takes about 5 minutes and I stopped when the temperature of the water more or less leveled off. The final water temperature in this experiment was 19.9^oC.