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Determining boiling points with small samples'

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Determining boiling points with small samples. ... Fasten the sample along side a thermometer bulb. Clamp the assembly in the oil bath. ... – PowerPoint PPT presentation

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Title: Determining boiling points with small samples'


1
Determining boiling points with small samples.
  • The Micro
  • Method

2
Determining boiling points with small samples.
  • and The Semi-
  • micro
    Method

3
Determining boiling points with small samples.
  • The first segment is taking boiling points by the
    micro method.
  • Several drops of sample will
  • be required for this method.

4
Place several drops in a 3 inch test tube and
invert a capillary tube into the sample.
  • Fasten the sample along side a thermometer bulb.

5
Clamp the assembly in the oil bath.
  • Take care that the rubber ring is not touched by
    the oil.

6
Heat and stir until a rapid stream of bubbles is
coming from the tube.
  • You are ABOVE the boiling point! Remove the
    burner, BUT KEEP STIRRING!!!

7
Continue to stir, and watch!! As the sample
cools, the stream of
  • bubbles slows down . . .

8
Continue to stir! The bubbles come slower and s
l o w e r
  • . . .and even s l o w e - r

9
Finally one bubble doesnt make it out! The
liquid runs back up the tube!Did you see it ???
  • Look at your thermometer!
  • THIS IS THE BOILING POINT!!

10
This segment is taking boiling points by the
semi-micro method
  • A milliliter or two of sample will be used in
    this method.

11
Start with a good ring stand.Tighten the rod!!
  • Add an iron ring about 6 7 inches up from the
    base.

12
You need a wire gauze with a ceramic center.
  • There should be a pencil-size hole in the
  • ceramic center.

13
Position the wire gauze on the iron ring.
14
Clamp a medium-size test tube on the hole -- no
air space!
  • Add a milliliter or two of the sample . . .
  • and one boiling stone.

15
Clamp the thermometer assembly . . .
  • . . . with its bulb centered an inch or two above
    the liquid sample.

16
Light the burner and adjust it to a small flame .
  • Play a small flame directly onto the hole in the
    wire gauze.

17
Bring the sample to a gentle boil.
  • Watch for steady drops falling off the
    thermometer bulb.

18
When the temperature becomes stable . . . no
longer rising . . .
  • Record the boiling point!

19
bp-rept.doc LABORATORY REPORT FORM DETERMINATION
OF BOILING POINTS NAME


Section Date__________________
_____
Record your comments regarding which of the two
methods gave you the better results. (You will
be using one or both methods when
you are trying to identify your unknowns.)
  • Your Laboratory Report Form is due the day on
    which you perform the Boiling Points Experiment.
    Be prepared to turn it in.
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