Melting Point Lab

What is the purpose of determining the melting point?

To determine the purity and identity of a compound

What equipment was used for this experiment?

Melting apparatus, one-end-closed capillary tubes

What should ALWAYS be run along side a sample in the apparatus?

A reference compound

How is the melting apparatus used?

1. The melting apparatus can hold up to 4 tubes (recommended to use 2 at a time)

2. Place tubes into apparatus

3. Set plateau to 10 degrees below the melting point of the reference compound

4. Once plateau is reached, begin ramping (~2 degree/min)

5. Watch closely to determine melting point range

Melting point definition

The temperature range at which a pure compound changes state from a solid to a liquid

How to impurities affect the MP range?

MP depression

How is MP determined?

The lowest temperature value is recorded when the first drop of liquid forms (NOT shrinking), and the highest temperature value is recorded when the entire sample has turned to liquid

How do you “correct“ a MP range?

Determine the difference between the highest value of the reference compound and its literature value, then apply this difference to BOTH values recorded for the sample