You can readily separate a mixture of salt and sand if you have water available. This separation makes use of the vast difference in solubility between the two solids; the salt will quickly dissolve and the sand will not. You can still separate the two if you don't have water, but you have to use a different approach. One method of separation makes use of the difference in the melting points between these solids. You need to heat salt to a very high temperature before it melts, but fortunately the standard lab Bunsen burner is capable of reaching that temperature.
- Metal wire mesh
- Ring stand
- Clamp support
- Bunsen burner
- Gas supply
Fix a section of wire mesh onto a clamp attached to a ring stand, so that the wire mesh is held horizontally about six inches above the lab bench top. The mesh should be just fine enough so that the salt and sand particles do not fall through it.
Place a few tablespoons of your salt/sand mixture on top of the wire mesh. Place the mixture on the mesh gently so that none of it falls through. It is helpful to know that the table salt in this mixture is known chemically as sodium chloride (NaCl). The sand will be primarily composed of silicon dioxide, sometimes known as silica (SiO2).
Place a beaker below the mesh. Turn on the gas supply to the Bunsen burner and light the burner.
Hold the Bunsen burner below and to the side of the mesh. Angle the burner so its flame goes through the base of the mesh and heats the mixture of salt and sand.
Maintain the flame on the mixture until the salt begins to melt and drip through the mesh into the beaker. The sand will be retained on top of the mesh. This occurs because the burner is only capable of heating materials to a temperature of approximately 1500 degrees Celsius. This is above the melting point of salt (NaCl) which is about 800 degrees, but SiO2 does not melt until at least 1550 degrees.