The Lead Dioxide Anode at Work
Entry posted by Swede
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After the preliminary microscopy photos, which will help me create some baseline images of the pristine anode surface, it was time (finally!) to actually power the darned thing, and make some perchlorate with it.
From the beginning, I have worked with potassium rather than sodium salts. Those who understand the chemistry of the process know that potassium is never used in major (per)chlorate plants due to the poor solubility... they always use sodium salts, and then convert the sodium (per)chlorate to everything from barium to ammonium perchlorate. Sodium chlorate is highly soluble, and the perchlorate, even more so. This means that high concentrations in the electrolyte are easy to achieve with sodium, but are much more challenging with potassium. To get a decent concentration and resultant yield with potassium salts requires two things... you must have a cell of adequate volume, and you must pre-heat the electrolyte to dissolve the potassium chlorate, then immediately begin electrolysis to keep the heat up, and prevent the chlorate salts from forming as the cell cools.
For reasonable production of perchlorate when starting with potassium chlorate, I'd recommend a minimum of 12 liters. 25 to 40 liters would probably be better. For testing purposes, though, there is no problem using a smaller container. In this case, I have gone back to a clear polycarbonate food container, brand name "Click-clack", for the first run, and it has a capacity of approximately 4 liters. The transparency was desirable so I could see how the anode is doing physically.
The first step was to dissolve an appropriate amount of potassium chlorate in tap water. Four liters was added to a bucket, an immersion heater added, and the temperature taken up to 50 degrees C. I plan on limiting the temperature of the cell to 60 degrees.
Into the four liters of water at 50 degrees went 600 grams of raw electrolytic KClO3. This is the chlorate harvested from previous runs, washed and dried, but not recrystallized. This means that there is going to be probably 2 to 4 grams of chloride in the liquor. Ideally, there'd be 0 grams, and for a platinum anode, recrystallization of the chlorate would be best, but in theory, chloride will not hurt a LD (Lead Dioxide) anode.
The small test cell was wired appropriately to my data-collection rig:
and the small notebook PC (using an 8 gig flash thumb drive) was fired up, using the DATAQ software for data collection of voltage, temperature, and current.
Right away, I noticed that the bucket cell hardware was definitely not optimized for an LD anode. The voltages required for perchlorate production are always higher than for chlorate, and ideally you'd want a pair of cathodes positioned closely to the anode. In my bucket cell adapter, I had spaced the electrodes by 1 inch or 25 mm (don't ask me why I did this) and the voltage required to obtain a decent current (17 amps) was quite high at about 8.5 V. I also used a small cathode which made the problem worse. If I had two cathodes, and correct spacing, the voltage would be probably around 6.5V.
The temperature of the liquor at the start of the run was 50 degrees C. Right away, at 17 amps, I noticed a temperature climb, which was good. It is not hard to control higher temps by using air or water to cool, but the only way to increase the temperature is with additional current or by physically insulating the cell. So I knew I could control the temperature and keep it below 60 degrees.
20 amps was my target, but 20 amps was pushing the voltage limits on my power supply, so I decided to keep it at 17.
With the data collection at work, I should have a good feeling for the efficiency of the cell. So far, all appears normal. Plenty of hydrogen evolution, and best of all, I am noticing a distinct odor of ozone, exactly the same as when Platinum is used. It's not a vague whiff but a fairly potent odor, which is vented to the outside. My plan is to add the ozone to the atmosphere, where it will help close the hole in the ozone layer in the arctic regions, and thus save the penguins.
Who said pyrotechnology is not green? 
I expect to see some solid perchlorate forming in a day or two. So far, everything looks excellent.
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