Experiment 1. Temperature and Pressure Calibration Temperature measurement tips are illustrated here for one of the setups at Station 4. The reference thermometer in this case is an electronic device which measures to the nearest 0.1° and is stated to be accurate to within 0.2°. Make sure that the thermistor (connected to wires) and the reference thermometer are immersed to a sufficient depth … but not so deep that they interfere with the stir bar. For this electronic thermometer, position the tip about an inch below the tip of the thermistor.

Proper adjustment of the stirring speed is important for achieving good mixing, leading to thermal equilibrium. It is easiest to collect data working down in T, but you should also collect some points with the bath warming up. To cool the bath, add small chunks of dry ice (at Stations 4 and 6) or ice (Station 3). Don’t add too much dry ice! Wait until all solid is gone before attempting a measurement: You do NOT have thermal equilibrium if solid is present! 2

For the calibration of the Baratron pressure gauge, you will use an open-ended mercury manometer, so you will have to measure the levels of the meniscus on both sides. Using a white card as an aid, you should be able to measure each level to the nearest ~1/3 mm. Take care not to subject the manometer to sudden large changes in pressure: Guess what happens to people who spill mercury in the laboratory! 3

The open end of the manometer is at atmospheric pressure, which you will measure precisely using the mercury barometer in the lab. This instrument is equipped with a vernier scale for precise measurement. For example, the vernier depicted here is reading 41.4 mm (actually Torr, the “7” being suppressed). The readings of this instrument and the manometer will have to be corrected for thermal expansion of Hg, as discussed in the writeup. 4 “41” “.4”

5 The LabWorks Interface used in this experiment is also used in Experiments 3, 4, and 6 to record temperature (and in Expt. 4, pressure) directly into a computer file, as a function of time. The computers will usually be ready to go, but if not, you can find the program easily and start it. The program logs data into a file, so that in case of a crash, all is not lost. However, this file is overwritten each time you start logging data, so you will need to select “Save” each time you stop logging. The program will store up to 2000 points before it stops on its own, but you can stop it at any time.