. c c . . c . c 2. c

E 1. Electrolysis Set-up

2. Electrolysis start

3. Pipette Eudiometer Set-up

4. Students activating the combustion

5. Fountain in action

Volumetric reaction of oxyhydrogen gas made by electrolysis in a pipette*)eudiometer

An eudiometer is an "instrument for measuring changes in volume during the combustion of gases, consisting of a graduated tube that is closed at one end and has two wires sealed into it, between which a spark may be passed". (http://www.answers.com/topic/eudiometer-2?cat=technology). 2. c c 2. c c 2. c c 2. c c 2. c c 2. c c 2. c c 2. c*) This experiment is a quantitative modification of an experiment, Professor Zhou first published 1992. Now it will be done with disposable materials.

In the following experiment the pipette serves two purposes 1. As electrolytic cell (Photos 1, 2) to produce the oxyhydrogen gas between two hypodermic needle electrodes and. 2. as eudiometer (Photos 3, 4, 5 ) "for measuring changes in volume during the combustion of gases". The pipette head is "the tube that is closed at one end and has two (pins) sealed into it." The spark is passed between them using a self-made piezoelectric igniter from an empty cigarette lighter.

Material
Tray, container for waste, plastic pipette with thin stem, ampoule 5 ml (high), stopper of an infusion bottle (stand), 4 pins, 2 insulated copper wires with crocodile clips,scissors, 9-Volt battery, piezoelectric igniter, plastic dropper bottle (10 ml) with a 10% aqueous sodium sulfate solution (Glauber Salt).
Procedure
1. Completely fill the plastic pipette with the Glauber Salt solution (Photo 1): Press the pipette head for a first time, dip the pipette tube into the solution, draw in the first part of the solution, then bend the pipette head downwards, press the pipette head again for complete removal of air and draw in more solution.
2. Pierce the pipette head from downside with 2 pins as electrodes.
3. Cut off 6 cm of the pipette stem, place the pipette into an empty ampoule fixed in a big stopper.
4. Photo 2: Connect the electrodes with a 9-Volt battery.
5. Photo 3: Wait until the liquid is replaced by gas. Pierce the upper part of the pipette head with 2 pins connected with the self-made piezoelectric igniter.
6. Photo 4 and 5: Press the button of the "piezo". Carefully observe ALL details during the reaction.
Observations
1. During electrolysis gas bubbles rise from both needles replacing the electrolyte that is transferred into the ampoule (Photos 1 - 3).
2. The colour of the electrolyte becomes brown. Brown solids appear. P...................ressing the but............................................................................................ton of the 3. Pressing the button of the piezoelectric igniter ("piezo") activates the reaction of the gas: Light, sound, compression of the pipette head, rise of the electrolyte (Photos 4, 5).

Explanation
a) During electrolysis the pipette head is filled with oxyhydrogen gas (about 3 ml). Not only water is oxidized at the anode producing oxygen.Beside that an anodic oxidation of iron takes place producing a brown solid.(
b) During its reaction oxyhydrogen gas disappears leaving a vacuum as the gas is replaced by a negligible volume of liquid water.
c) The pipette head collapses due to the air pressure (Photo 5). The elastic properties of the plastic material cause a fountain effect.
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