The melting point of the re-crystallized salicylic acid has given a range of two or three.......

Question

The melting point of the re-crystallized salicylic acid has given a range of two or three degrees, with upper limit of the range slightly below the (real) literature value of the melting point of salicylic acid, 159 ºC. What can you do to the product to obtain a melting point closer to the literature value? 

Answer 1

To obtain a melting point closer to the literature value of salicylic acid, the following steps can be taken:

Purification: Ensure that the recrystallization process is performed accurately to obtain a pure sample of salicylic acid. Impurities can affect the melting point and result in a broader range. Use a suitable solvent for recrystallization and employ proper techniques such as filtration and washing to remove impurities.

Drying: Ensure that the recrystallized salicylic acid is thoroughly dried before taking the melting point. Moisture in the sample can lead to inaccurate readings and a broader melting point range. Use a desiccator or drying oven to remove any residual moisture.

Sample preparation: Prepare a small amount of finely powdered or well-crushed sample for the melting point determination. This helps ensure uniform heating and accurate measurement of the melting point.

Calibration: Calibrate the melting point apparatus to ensure accurate temperature measurement. Use known reference substances with established melting points to verify the accuracy of the apparatus.

Heating rate: Control the heating rate during the melting point determination. Slow and steady heating allows for better observation and accurate determination of the melting point. Rapid heating can result in an inaccurate and broader range.

By carefully following these steps, it is possible to obtain a more precise melting point closer to the literature value of salicylic acid (159 ºC).