Naphthalene Chromatography

Abstract Finding the melting point of an organic substance is a practical and efficient way for scientists to identify an unknown substance or determine a known substance's level of purity. When organic substances are mixed together in varying degrees they take on a melting characteristic that is lower and broader than in its pure form. This property was manipulated in the lab to observe the various melting points of Naphthalene and Biphenyl when the percentage of composition was altered. A eutectic point of 45 °C at 52% Naphthalene was determined from the class data. An unknown crystalline substance was identified to be Benzophenone by mixing and finding its melting point with known substances.

Introduction Organic compounds are categorized by their physical properties and/or chemical reactions. Naphthalene is classified as an aromatic hydrocarbon that consists of two benzene rings that are fused together. Its physical
The samples were then attached to a thermometer and placed in a Thiele tube filled with oil. The tube was heated by a Bunsen burner at approximately 1 °C per minute. Melting point temperatures were recorded at the first indication of fluid and then when the sample had turned completely liquid. Two trials were completed on each sample ². The melting point of 10% naphthalene / 90% Biphenyl mixture was determined by electronic instrumentation. Two samples were prepared and placed in closed end capillary tubes and then inserted into the "Mel-Temp" device beginning at 30°C and set at 22 volts to ensure gradual heating; approximately 1°C per minute. Two trials were completed on each sample. The results were then categorized and combined with other data sets collected by the laboratory students. This data was then used to find the eutectic point of the two substances