Chemistry Reference
In-Depth Information
a crust- and kerosene-free piece of sodium is to be heated in the test tube until
sodium melts and lights up (see figure).
Sodium
Chlorine
The chlorine is to be passed over sodium slowly with the help of the gas syringe
until a yellow flame appears. Slowly all chlorine of the syringe is to be passed over
the burning sodium. The white substance on the glass tube can be tasted.
Observation: Sodium reacts with chlorine forming a luminous yellow flame; white
powder settles out on the glass tube and inside the test tube: it tastes like table salt.
Please note: The damaged test tube might contain remainder of sodium. Ethanol is
to be added carefully, the test tube is to be rinsed with water and disposed off in the
glass waste.
E5.8: Flame Colors of Alkaline Metal Salts
Problem: When alkaline metals burn in air, the emerging flames show a characteristic
color. These colors can also be observed when the salts of alkaline metals are being eva-
porated in the hot burner flame. These colorations can be useful for analytical purposes.
Material: 3 watch glasses, cobalt glass; magnesium oxide rods, lithium chloride
(Xn), sodium and potassium chloride.
Procedure: A small amount of lithium chloride is to be put on a watch glass, on
a second glass a small amount of sodium chloride and on a third glass a small amount
of potassium chloride. These samples are to be wet with a little water. The magnesia
rod has to glow in the gas burner flame until the flame does not glow yellow anymore.
Now the magnesia rod is to be dipped into one of the salts and then put into the gas
burner flame. The potassium flame is to be watched through a cobalt glass.
Observation: The burner flame is colored bright red, yellow, and violet by the salts
in the stated order. The last color can be seen easier, if the flame is being watched
through a blue cobalt glass: the yellow flame that is caused by traces of sodium salts
is being absorbed by the blue-colored glass.
E5.9: Electrolysis of Lithium Chloride-Melt
Problem: Solutions of alkaline metal salts can be electrolyzed without difficulty,
but instead of the expected metal, hydrogen forms at the cathode. Therefore this
experiment shows exemplarily that instead of a solution, a melt is to be used to get
the elemental base metal. During this fused-salt electrolysis two technical problems
occur: working at high temperatures and a high current flow.
So a mixture of salts is used to lower the melting temperature; and the direct current
voltage source has to be secured for a high current flow of up to 10 A.
