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Method of mixed melting points
We have just made a substance which has the same (or very similar) melting point as the material we were aiming to make. It seems highly likely that we have been successful in making the right material. However, the fact that the melting points are identical does not prove that the materials are identical. It could just be a coincidence that the melting points match. Particularly where the material is to be used as a drug, it is critical that we are sure we have the right substance. This can be done using the method of mixed melting points.
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In this method, a sample of the suspect material is mixed with a sample of the pure target substance, and the melting point of the mixture is measured. If we have the correct material, then the mixture is still the pure substance, and will melt at the same temperature. However, if we have a sample of another material with the same melting point, then the mixture of substances will not be pure. The presence of an impurity lowers the melting point of the mixture, and a reduced melting point with a wider range will be measured. |
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