# Measuring a Melting Point

## Using a Thomas Hoover Melting Point Apparatus™

A Description

### A Mel-Temp™ is commonly used to measure the melting points of compounds. A sample is loaded into a capillary tube and placed into the Mel-Temp™. While the tube is being viewed through an eyepiece, the Mel-Temp™ gradually heats the sample. By carefully observing the temperature range at which the sample turns from a solid into a liquid, the melting point is determined.

Preparing a Sample

### First, the sample should be crushed to a fine powder.

Video: Crushing the sample (3.20M ) Text description

### Next, the sample is loaded into a capillary tube.

Video: Filling a capillary tube (1.98M ) Text description

### If the solid will not go to the bottom of the capillary tube when the tube is tapped on a hard surface, drop the tube through a long, narrow cylinder.

Video: Dropping down cylinder ( 1.71M )

### Why is this sample not appropriate for use in a melting point experiment?Answer

Measuring the Melting Point

### The Mel-Temp™ can hold up to three samples at once.

Video: More than one sample ( 1.69M )

### Turn the heating stage on to a medium setting. This setting should result in a heating rate of about 15 degrees per minute.

Video: What does 15 degrees per minute look like? ( 2.75M )

### If you are unsure what the melting point of your sample should be, perform an initial melting point experiment in which you melt the sample rapidly to determine the approximate melting point. Then perform another experiment using the technique described above to measure the melting point of the sample more accurately.

Video: What does one degree per minute look like? ( 2.92M )

### Instead of recording one temperature as the melting point, measure the melting point range. To measure the range, record the temperature at which the solid first begins to turn to liquid and the temperature at which the solid has melted completely. The melting range may span several degrees.

Video: Recording a melting range ( 8.34 M )

Video ( 8.55M )

### What is wrong with this student's work? Answer

Using a Thomas Hoover Melting Point Apparatus™

### To measure a melting point using a Hoover apparatus, prepare the sample in a capillary tube as described previously. If the sample has not been packed well into the capillary tube, place the tube into the vibrator compartment near the back of the machine and turn the vibrator on briefly. The button must be held continuously for the vibrator to work.

Video: Using the vibrator to pack the sample ( 3.20 M )