Title:  Determination of Molecular Weight by Freezing Point Depression

Time Estimate:  2:30

Equipment Needed:

Test tube - large
wire stirrer
thermometer - Special .01^oC readable.  ASTM 89^oC
clamp
ringstand
Large Beaker for cooling bath (~500mL)
two-hole stopper (#4) split or some sort of thermometer holder

Chemicals Needed:

table salt
Ice
Unknowns:  Methanol, Isopropanol, acetone

Special Precautions:

Suggested Instructions:

The thermometers are very expensive.  Emphasize to handle carefully - always have
them secured.  Do not force them into holder stoppers.  Do not shake them down.

In the previous lab period, tell them to review colligative properties expecially freezing
point depression.

A good mix to use for this experiment is what is suggested by question 6.  Suggest
amount would be about 20 mL of water and 2 mL of unknown.  In order to cut down
on vaporization of the unknown, suggest that the weigh the water, add the unknown
and weigh again.

The thermometers tend develop a mercury break.  Check to determine if any Hg is
left in the upper bulb if the temperature seems to be far off.

For a 500mL beaker half full of ice, about 10mL (solid) of regular table salt is
sufficient to lower the temperature about 3-4^oC.