What should be done if the melting point is missed during its determination?

When determining the melting point of a substance, it is crucial to accurately capture the range in which the solid begins to melt. If the melting point is missed, allowing the apparatus to cool and starting again with a new sample is the best approach. This method ensures that fresh material is introduced into the system, providing a more precise reading of the melting point.

Starting over with a new sample is important because the original sample may have experienced some degradation or changes in its physical properties due to prolonged heating. Fresh samples give a better chance of obtaining consistent and accurate results. Additionally, repeating the melting point determination helps confirm that the first result wasn't influenced by an error in technique or equipment function.

Using a higher temperature without starting anew may lead to inaccuracies and potential decomposition of the substance. Meanwhile, recording the temperature that was reached does provide data, but it does not rectify the missed determination—merely noting the temperature means the melting point has not been confirmed, and taking corrective actions afterward is not optimal. Adjusting the thermometer setting may not be necessary, as inaccuracies are more likely due to sample conditions or method rather than a faulty thermometer.