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Thread: Electrolysis experiments
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25th March 2014, 12:07 AM #1
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Electrolysis experiments
Back in 2011 I posted a thread called “Electrolysis using an old computer power supply”https://www.woodworkforums.com/f65/electrolysis-using-computer-power-supply-134107
Since then I have done a few things with my old setup but recently I switched to using carbon arc welding rods and have been pleasantly surprised by a few things
The first is the significantly reduced amount of mess. Using a steel positive electrode generates copies amounts of red/brown/black frothy goo some of which floats to the top and some sediments to the bottom of the tank which makes cleaning up a nuisance.
The second problem when using a steel electrode is the red goo coats the electrode and slowly reduces and even stops current flow and the rust removal process. The only way to restore the current is then to wipe the goo off the electrode and this needs to be done every few hours meaning overnight operation is not productive. None of these problems arise with the Carbon rod electrode,
Using carbon there is no goo no deal with and a constant current flows although I would expect some slowing down if it was run for long enough. The electrolyte turns a semi transparent grey but cleaning up is also much easier.
One thing I said I would do was measure the amount of Cr that would be lost when using a SS positive electrode. The concern here was how much shed occupants would be exposed to toxic CrO3 .
So I took a small bar off SS (50 x 25 x 3 mm) and weighed it and then used it in my (~1L) electrolysis tank for 6 hours and I measured ZERO change in the weight of the SS bar.
I use sodium carbonate as the electrolyte and used a conservative current of 2A
My balance's limit of reading is 10 mg so that means the most SS that could have dissolved is 10 mg.
Chromium is about 10% of SS so that means the most Cr that could have dissolved is 1 mg.
The first thing to look at is air. If all of that 1 mg of Cr was to get into the shed air (i.e. very unlikely) the concentration of Cr in my 128 m3 shed shed would be about 10 µg/m3
The recommended levels for Cr in air ranges from 5 µg/m3 in the US to 50 µg/m3 in most European countries.
I seriously doubt that even 1/100th of the 1mg of Cr would get into the air from the tanks, and adding some ventilation will drop things even further, so the Cr levels in the air appear to be insignificant
The next issue is one of disposal of the electrolyte.
In the US water is not supposed to be disposed of with a Cr concentration of more than 0.1 mg/L so to dispose of the theoretical 1mg of Cr, all that would be needed is 10L of water.
In fact putting it down a domestic drain in a busy suburb means it will be rapidly diluted by domestic water use.
If you want to be really sure and get it to groundwater levels you'd need about 200L of water. But once again it is unlikely that there is 1mg of Cr there to begin with.
The experiment is not over - I want to run the electrolysis tanks at higher voltages and currents and use a more sensitive balance.
Please note that the electrolyte is sodium carbonate, if you were to use something more acidic then things could change significantly.
Bottom line so far is, 1L tank, small SS electrode, 2A, sodium carbonate electrolyte looks OK.
And yes, I would feel safe using it under these conditions.
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