Part I. Freezing Point of the Solvent:

Computer Set-Up: follow directions given for the ULI setup and calibration

Solvent Preparation:
Obtain a small test tube (75 mm x 10 mm). Add about 150-250 mg of sample to the test tube and record its exact mass. (Use the 4-place balance.)

Place the tube in a 50 mL beaker half-full of boiling water. After the sample has melted remove the heat, insert the temperature probe (or thermister) into the sample, and clamp a thermometer into the beaker of hot water. Be careful not to allow water in the sample. Stir the sample gently with the thermister while watching the water temperature drop.

When the water (and sample) temperature has dropped to 65 ^oC, start sampling and graphing the data.

Analysis of Data:

Press the arrows to move the cursor along the lines to determine the point of intersection, which is the melting temperature of the solvent. Record this temperature. (Alternately, the freezing temperature can be observed directly from the graph by moving the cursor to that point and reading the temperature from the screen.)

Part II. Freezing Point of the Solution:

Sample Preparation:

Mass out 1.5-2.5 mg of solute to the nearest 0.1 mg into a small dry test tube. Place the the tube with the solvent and thermister back into the beaker of boiling water. Remove the thermister after the solvent melts and add the solute sample prepared above. Remove the heat and stir the solution gently with the thermister. When the water (and sample) temperature has dropped to 70 ^oC start sampling. Watch the sample carefully and note the temperature at which the solution appears to be solidifying.

Follow procedures described above for sampling, saving and plotting the data.

Analysis of Data:

Use the cursor and see if you can determine when the solution first begins to freeze out and record this as the freezing point of the solution. Compare this point with the one you recorded from your observation above.