Question

1. Why is it important to heat the sample in the MelTemp slowly to obtain an accurate melting point? If your sample starts to melt before you can start recording the melting point range, should you cool the capillary tube and reheat it to determine the melting point range again or start with a fresh sample? Why?

Answer 1

Dear Student,

Melting point is the temperature at which solid starts melting. In simple words, we can say it is the temperature at which the solid state changes into the liquid state.

While measuring the melting point of the compound, the compound should be completely dried, homogeneous and should be in fine powdered form. It is always recommended to measure the melting point of the compound at a slow heating rate ( 1-2 degree celsius) in order to get the accurate measurement. We will record the temperature at which sample first starts to melt and the temperature when all the sample has melted. Now if we don't maintain a slow heating rate, we will miss the exact temperature at which solid first melts because high heating results in rapid melting of the sample.

It is not advised to cool the capillary and reheat the sample, because on cooling or solidification there are certain possibilities that can occur:

1. While solidification, the impurities are introduced in the sample which will interfere with the melting point.

2. While solidification, it is possible we do not get the proper dry and crystalline compound that we have at the starting of the experiment.

Thus, always use a fresh sample and fresh capillary tube to obtain accurate results.

Best Wishes!