Identification of an Unknown Organic Compound by Determination of its Melting Point

The melting point is very useful information for identifying an unidentified organic substance. It is also helpful to define the purity of the substance. Pure substances have a melting point range of 1-2oC, while the impurities lower the melting point and increase the melting range. In a mixture of two substances, the melting point can be calculated by creating a two-phase melting diagram. The lowest temperature at which the melting point of a mixture can be reduced is called the eutectic point. The melting point is measured on a special heated apparatus using a glass capillary tube. The sample is placed in the tube, which is heated in the device. In the following study, the melting point of an unknown organic compound was measured by the fast and the slow rate heating method. The melting point of the sample showed that the chemical compound to be identified was either acetanilide or 4-nitrophenol. Equal amounts of the unknown substance and acetanilide were mixed, and the melting point was estimated for the mixture. If the mixture has a lower melting point compared to that of the unknown compound, then the two compounds are different, and one acts as an impurity to the other. The mixture had a similar melting point to that of the unknown compound, and therefore the unknown compound was identified as acetanilide C6H5NH(COCH3).