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Lecture 4

CHEM 235 Lecture Notes - Lecture 4: Drop Tube, Waste Container, Spatula


Department
Chemistry
Course Code
CHEM 235
Professor
Dana Zendrowski
Lecture
4

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PURPOSE
To illustrate the effect of an impurity on the melting point of a pure compound.
NOTES
Melting point: temperature at which the crystalline solid and the corresponding liquid
phase are at equilibrium (under external pressure of 1 atm)
Requires thermometer
and a heating
device
that is in close contact with the thermometer
bulb.
Heater may be: a liquid bath or a metal block
M.p. range: measured from the temperature when the first drop of liquid appears amongst
the crystals to temperature at which complete liquification takes place.
Pure organic compounds: sharp melting points (range 1-2˚C)
Impurities (including residual solvent):
- lower m.p.
- wider m.p. Range
Melting point apparatus
1) Fisher-Johns m.p. apparatus
2) Mel-Temp apparatus
Calibration equation: Y = MX + B
Y: true temperature reading
X: experimental temperature reading
M, B: numerical values provided on individual apparatus
EQUIPMENT:
2 watchglasses Microcoverglasses & capillary tubes
large test tube 400 mL plastic beaker (for ice bath)
spatula melting point apparatus
CHEMICAL HAZARDS AND WASTE DISPOSAL
Benzoin & Trans-cinnamic acid
- Use cautiously
- Put in “solid waste” container
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