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If you have LOTS of sample, you can determine the boiling point by distilling the sample. This provides the b.p. AND it cleans up the sample. However,

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Presentation on theme: "If you have LOTS of sample, you can determine the boiling point by distilling the sample. This provides the b.p. AND it cleans up the sample. However,"— Presentation transcript:

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2 If you have LOTS of sample, you can determine the boiling point by distilling the sample. This provides the b.p. AND it cleans up the sample. However, if you have only a few milliliters (or even less), you must use other methods.

3 Determining boiling points with small samples. The Micro The Micro Method Method

4 Determining boiling points with small samples. andThe Semi- and The Semi- micro Method micro Method

5 Determining boiling points with small samples 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.

6 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.

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

8 Heat and stir until a rapid stream of bubbles is coming from the tube 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!!!

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

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

11 Finally one bubble doesn’t make it out! The liquid runs back up the tube! Did you see it ??? Look at your thermometer! THIS IS THE BOILING POINT!!

12 Use a different test tube for each sample Use a different test tube for each sample. When you have finished, CLEAN and DRY the 3-inch test tubes. Keep them in your lab drawer. They will be used again next week in Sodium Fusions.When you have finished, CLEAN and DRY the 3-inch test tubes. Keep them in your lab drawer. They will be used again next week in Sodium Fusions.

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

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

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

16 Position the wire gauze on the iron ring.

17 Clamp a medium-size test tube on the hole; -- no air space! Add a milliliter or two of the sample... and one boiling stone.

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

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

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

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

22 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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