The Melting Point Experiment

Melting point (solids only). This is a range, like M.P. 96-98°C (see Chapter 9, The Melting Point Experiment ). 

With the Thiele tube (Fig. 39) you use hot oil to transfer heat evenly to your sample in a melting point capillary, just like the metal block of the Mel-Temp apparatus does. You heat the oil in the sidearm and it expands. The hot oil goes up the sidearm, warming your sample and thermometer as it touches them. Now, the oil is cooler and it falls to the bottom of the tube where it is heated again by a burner. This cycle goes on automatically as you do the melting point experiment in the Thiele tube. 

Make sure the ENTIRE thermometer bulb is below the sidearm of the 3-way adapter. If you don t have liquid droplets condensing on the thermometer bulb, the temperature you read is nonsense. Keep a record of the temperature of the liquid or liquids that are distilling. It s a check on the purity. Liquid collected over a 2 ° C range is fairly pure. Note the similarity of this range with that of the melting point of a pure compound (see Chapter 9, The Melting Point Experiment ). 

Here you stop the distillation and change the receiver. Now in one receiver you have a pure liquid, B.P. 49-51°C. Note this boiling range. It is just as good a test of purity as a melting point is for solids (see Chapter 11, The Melting Point Experiment ). 

When you re through cooling, filter the crystals on a Buchner funnel. Dry them and take a melting point, as described in Chapter 12, The Melting Point Experiment. ... 

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