Water bath

A simple water bath

This is a more gentle method of heating than using a Bunsen burner directly. A simple water bath is just a beaker of water being heated by a Bunsen over a tripod and gauze. It has a number of advantages over direct heating. The test tube being heated is further away from the naked Bunsen flame, so there is less chance that any flammable vapours will catch fire (but beware, it is still possible!). The water in the bath has a high heat capacity, so there is a much more gradual change in temperature. The maximum temperature cannot exceed 100 °C, and the contents of your test tube are less likely to bump. Obviously, this method is unsatisfactory if you need to raise the temperature higher. You may get around this in your melting point work by using an oil bath.

Students tend to fill their water baths too full. When it starts to boil the hot water may well jump out of the beaker. A half-full beaker is generally satisfactory and it will get to the boil much quicker than a full beaker! Don't forget that even if your water bath is not completely full, when you add a few test tubes to it, the level of the water will rise.

An electric, thermostatically controlled water bath

You may also use a thermostatic, electrically heated bath.