Melting Point
Introduction The purpose of the experiment was to determine the melting points of compounds using a Mel-Temp device. The melting point of naphthalene, urea, and sulfanilamide are found. This is then followed by the measuring of an unknown compound, and an impure sample (a small amount of naphthalene mixed with the unknown).
Experiment
In the lab, the height of the chemical in the capillary was set to 2-3 mm thickness. The voltage at the Mel-Temp started at a low setting of 1.5-2. The heat was lowered when the temperature reached within 10 degrees of the MP range. The voltage was kept an eye on so as to have the temperature increase by 1 degree every half minute. The first drop of naphthalene was seen at 78 degrees. The solid fully melted at 80 degrees Celsius. A separate Mel- Temp was used to avoid the cooling wait time and the process was repeated with Urea. The first drop of liquid appeared at 132, and the melting finished at 134. Yet again, the Sulfanilamide was tested and seen to show a range of 165-167 degrees for its melting point. The same set up for the apparatus stated above was used with an unknown compound (#2). The compound was heated quickly in one Mel-Temp to 132, where it began to melt at a voltage reading of 4. Another, cooled Mel-Temp was used to narrow down the range of the melting point to 132 to 134. A mix of Naphthalene and the unknown compound was heated in the Mel-Temp to 132, where the first drop of liquid appeared. It finished melting at 134 degrees. The apparatus was turned off, including the voltage and digital thermometer. The used capillaries were placed in the dish next to the equipment.
Results
Compound
MP Range (Celsius)
Naphthalene
78-80
Urea
133-136
Sulfanilamide
164-166
Unknown #2
134-135
Impurities
132-134
Discussion For the first part of the lab, the melting points of the known compounds were accurate. The naphthalene should have been 79-80°, the Urea 132-134°, and the Sulfanilamide 165-167°. The experimental ranges
Experiment
In the lab, the height of the chemical in the capillary was set to 2-3 mm thickness. The voltage at the Mel-Temp started at a low setting of 1.5-2. The heat was lowered when the temperature reached within 10 degrees of the MP range. The voltage was kept an eye on so as to have the temperature increase by 1 degree every half minute. The first drop of naphthalene was seen at 78 degrees. The solid fully melted at 80 degrees Celsius. A separate Mel- Temp was used to avoid the cooling wait time and the process was repeated with Urea. The first drop of liquid appeared at 132, and the melting finished at 134. Yet again, the Sulfanilamide was tested and seen to show a range of 165-167 degrees for its melting point. The same set up for the apparatus stated above was used with an unknown compound (#2). The compound was heated quickly in one Mel-Temp to 132, where it began to melt at a voltage reading of 4. Another, cooled Mel-Temp was used to narrow down the range of the melting point to 132 to 134. A mix of Naphthalene and the unknown compound was heated in the Mel-Temp to 132, where the first drop of liquid appeared. It finished melting at 134 degrees. The apparatus was turned off, including the voltage and digital thermometer. The used capillaries were placed in the dish next to the equipment.
Results
Compound
MP Range (Celsius)
Naphthalene
78-80
Urea
133-136
Sulfanilamide
164-166
Unknown #2
134-135
Impurities
132-134
Discussion For the first part of the lab, the melting points of the known compounds were accurate. The naphthalene should have been 79-80°, the Urea 132-134°, and the Sulfanilamide 165-167°. The experimental ranges