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5.7 Melting Point

5.7.1 Overview

The melting point (or, rarely, liquefaction point) of a solid is the temperature at which it changes state from solid to liquid at atmospheric pressure. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard pressure. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point or crystallization point. Because of the ability of some substances to supercool, the freezing point is not considered as a characteristic property of a substance. When the "characteristic freezing point" of a substance is determined, in fact the actual methodology is almost always "the principle of observing the disappearance rather than the formation of ice", that is, the melting point.

5.7.2 Procedure

1. Retrieve some miligrams of your solid sample with the spatule to a small tube.
2. Now with a microcapillary, try to collect some of the sample you retrieved to the tube. Doing this, you should turn the microcapillary around to get the sample to its bottom.
3. Should look aproximatelly like this, just enough amount to make it possible to see in the machine.
4. Insert the microcapillary in the Melting Point machine, if only one sample is necessary to test, then it should be located in the center position. Insert the thermometer.
5. Turn on the device and increase the temperature (variable heater).

6. Keep your sample under watch through the hole, where you should note the initial moment that it starts melting, its your melting point signalled by the thermometer.

7. Be careful handling the thermometer when the measuring is over, for it is really hot due to the high rise of temperature.


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