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Alan Slater, St. Marys ON KISS !!! Keep It Simple & Safe. That is #1 for me and it also stands for microchemistry. A simple, safe fuel cell Reprinted from page 34, October 1999 Looking ahead to the new millenium I thought that this idea was most appropriate. As well, it illustrates the result of the sharing of ideas that Reg Friesen encouraged us all to do through this magazine and various conferences. I made fuel cells some 25 years ago but used 2 M NaOH which is quite corrosive and eats away at corks. At Chem Ed 97 Lynne Hogue (Miami University, Ohio) showed the simple electrolysis of water with 2 pencils, using a saturated solution of Epsom salts (MgSO4•7H2O). In earlier issues of Chem 13 News I have mentioned uses of Epsom salts! Why didn’t I see this one?!! Epsom salts solution – Place Epsom salts in one well to about 1/3 full and fill with water. Use a thin stem pipet to mix and dissolve the Epsom salts. Draw up most of the solution into the pipet leaving the well about 1/4 full of solution. Place the thin stem into an inverted electrode tube and slowly dispense the solution into the narrow tube. Remove the thin stem as the tube fills. Make sure that the solution beads up on the end then invert the electrodes and place them into the 24-well plate. It is very important NOT to get an air bubble at this end or you will not have a complete circuit. Fill the other electrode tube the same way. To ensure there is a complete circuit you can test with a multimeter across the two electrodes. I always had problems with leaks also. Microchemistry solved that problem, for which I am indebted to Brother Carmen’s idea of electrolysis using two narrow tubes in a 24-well reaction plate (see the diagram). Finally, a good seal can be made simply and quickly using a hot glue gun. Thus a newer, simpler, safer electrolysis-of-water apparatus was born. BUT, more importantly a fuel cell was also made. The fuel cell reactions are: 9-V battery C-electrode glue plug Red’n ½ O2 + 2 H+ + 2 e– → H2O Eo = + 1.23 V Oxid’n H2 + 2 OH– → 2 H2O + 2 e– Eo = + 0.83 V Overall H2 + ½ O2 → H2O ΔEo = + 2.06 V plastic tube 24 well plate MgSO4(aq) Equipment Carbon electrodes – A drafting pencil lead from a stationery store can be snapped in two to make two carbon electrodes. Electrode tubes – I use 2- or 5-mL disposable serological pipets that can be cut into at least four smaller sections. This gives you a scale to measure gas volumes. If the measuring aspect is not important use a Bic pen barrel (clear plastic) and cut it into 2 pieces. Glue plug – Place the carbon electrode in the tube as in the diagram. Squeeze some hot glue around the carbon electrode and immediately immerse this end vertically into cold water. This will set the glue AND test for any leaks. 24-Well reaction plate – This is the ‘beaker’ for the electrolysis/ fuel cell solution. If you use a comboplate well it is too small for two tubes cut from a 5 mL serological pipet (Bic pen barrels are fine). You could even use a bottle cap for this. Cell operation Attach a 9-V battery clip and alligators to the two electrodes, then attach the 9-V battery. In a few seconds gas bubbles should be seen at each electrode as hydrogen and oxygen are produced. Some of these gases will absorb into the carbon electrodes thus creating the necessary criteria for a fuel cell. To set up the fuel cell all you need to do is disconnect the battery and battery clips, set a multimeter to the 2-V scale and attach it across the two electrodes. A voltage of about 1.7 V should be found. Questions to consider could be: How long will this cell last? Does this time depend on how long the electrolysis ran? What effect would a larger/smaller diameter electrode have? ∎ September 2008/CHEM 13 NEWS 15