Boiling point is the temperature at which a liquid changes from a solid to a gas (vapor) at normal atmospheric pressure. It takes much more energy to convert a liquid into a vapor than it does to raise the temperature of the liquid itself. When a liquid reaches its boiling point it will begin to fill the capillary tube; this is known as boiling up. It is important to know the boiling point of a sample because it is a good indicator of its solubility.
Often times it is necessary to determine the boiling point of complex compounds. In these cases, the best method for obtaining this value is to use a reflux setup. This technique is similar to a distillation apparatus but is more economical because the boiling and condensing of a mixture occurs in one tube.
A good quality thermometer is essential for this experiment. The Safety Emporium sells a wide variety of thermometers that are ideal for determining the boiling point of chemicals.
The first step in determining the boiling point of cao is to prepare a test tube by sealing it with an oiled rubber band. The test tube should then be fitted with a capillary tube, closed end up. The capillary tube is then attached to a glass thermometer via a small rubber band. The test tube is then heated slowly until a vigorous stream of bubbles begins to emerge from the capillary tube. This should be done in a slow and continuous manner, as stops and starts have been shown to interfere with the results.