Microscale Chemistry Experimentation for Teachers
. 
..
..
11.
Chlor alkali electrolysis with micro tubes
Two 5-ml micro tubes are used for this
experiment and the electrolysis time is only a few minutes.
* The anode tube is filled with brine,
coloured with a drop of universal indicator (UI).
The anode electrode is a
piece of carbon from a pencil. being connected to the bare end of an isolated
copper wire by a tube.
This electrode is fixed inside
the micro tube which is closed by piece of tissue paper.
* The same is done for the cathode tube.
The cathode electrode to be inserted into it will be copper.
* A current is applied from an AC/DC converter.
A voltage is chosen to have a current of around 100 mA.
Hydrogen will collect
in the cathode tube and simultaneously the liquid will be blue due to accumulation
of hydroxide ions resulting from the reduction of the water molecules.
Chlorine
will collect in the anode tube simultaneously. UI turns red first
due to accumulation of hydroxonium ions resulting from the oxidation of
the water molecules. After a short time UI is decolorized by the chlorine.
The characteristic identification
tests for chlorine and hydrogen can be be applied to the samples
generated after electrolysis..
Electric conductivity
of solutions ...................................................................An
alternative using syringes