[Orgo Lab 2] Melting-Point Apparatus

Obtain a glass capillary tube and gently tap its open end on the solid sample to introduce material. Invert the tube and tap it on a flat surface to drop the solid to the bottom, aiming for a sample height of 2-3 millimeters. Use a long vertical tube to drop and bounce the capillary 3-4 times to pack the sample firmly at the bottom.

Turn on the light of the apparatus and insert the packed capillary tube into the sample chamber via the holes on either side of the heating block. Look through the magnifier and position the viewing tube so the sample is clearly visible.

Press and hold the plateau set button until the plateau light flashes and the display shows the current plateau temperature. Use the arrow keys to adjust the temperature to 5-10 degrees Celsius below the expected melting point, then release the button. Press the start key to begin rapid heating to the plateau temperature.

After the apparatus reaches the plateau temperature, press the start button again to resume heating at a much slower rate of approximately 2 degrees Celsius per minute. The ramping light will illuminate during this slow heating phase.

Carefully observe the sample through the viewing tube and record the temperature when the solid just begins to melt (lower value) and when complete liquefaction occurs (upper value). Keep the capillary tube in the apparatus during measurement to ensure accurate readings. Press stop after complete melting and allow the apparatus to cool slowly.

Allow the apparatus to cool down to at least 30 degrees Celsius below the melting point before inserting a fresh capillary tube for another trial. This prevents temperature reading deviations and ensures accurate measurements.

For new compounds with unknown melting points, set the plateau at 200 degrees Celsius initially to rapidly heat and obtain a rough melting point estimate. Once you observe melting, stop the operation and cool the apparatus. Then restart with a new fresh sample, setting the plateau 5-10 degrees below the rough estimate for an accurate measurement at the slower heating rate.