TLDR;
This video provides a guide on how to prepare a sample for melting point determination, a common technique for characterising and assessing the purity of solid compounds. It covers grinding the sample into a powder, filling the melting point capillary tube, packing the sample, and sealing the tube for substances that sublime easily.
- Grinding the solid sample into a fine powder ensures easy entry into the melting point tube.
- Packing the capillary tube with approximately one millimetre of the sample is essential for accurate melting point determination.
- Sealing one end of the capillary tube is necessary for substances that sublime easily to prevent loss of the sample during heating.
Introduction to Melting Point Determination [0:05]
The most common method for characterising a solid and assessing its purity is by determining its melting point. This process involves introducing a sample into a melting point capillary tube, which is open at one end and closed at the other.
Sample Preparation [0:24]
To prepare the sample, it should be ground into a fine powder to facilitate easy insertion into the melting point tube. The open end of the tube is then pressed into the powdered solid to collect some material. The tube can be tapped to pack the sample down, or a more effective method involves bouncing the capillary tube inside a condenser to pack approximately one millimetre of the material into the bottom of the tube.
Sealing the Capillary Tube [1:21]
For solids that sublime easily, it is necessary to seal one end of the capillary tube. This is achieved by heating the tip of the capillary in the hottest part of a Bunsen burner flame, which is at the top of the blue column. Rolling the tip in the flame until it becomes red hot causes it to collapse and seal. Once sealed, the tube is ready for insertion into the melting point apparatus to record the melting point range.
