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Turn the heating stage on to a medium setting. This setting should result in a heating
rate of about 15 degrees per minute.
Carefully observe the sample through the eyepiece. About ten degrees before the
temperature approaches the expected melting point, reduce the rate
of heating to one degree per minute.
The phase change for most pure substances occurs over a very narrow temperature
range (~0.1°C). However, some samples and samples that are contaminated will have broad
melting ranges. Thus, it is important to note the temperature where the solid first begins to appear wetted (small amounts of the solid appear to melt) and the temperature when the entire sample is a liquid. In these cases, a melting point range should be reported (initial wetting to complete melting temperatures).
The melting range, if measured properly, can give you useful information about a sample. If the melting range is small (about one degree), then the sample is probably fairly pure. However, if the range is large, or if it is below a known value for the melting point of the substance,
then the sample is probably impure.
Unless directed otherwise, discard used capillary tubes into a container for broken
glass. Before taking another melting point, be sure that the melting point apparatus is cool.
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