Today I have all the things fixed as they should be: correct distance (37 mm), correct amount of electrolyte drops (5 for 250ml), 1/2 teaspoon of maltodextrin. Heated up, but not boiling. No stirring.
I started of with a 2mm stainless steel cathode, and the voltage immediately collapses. As suggested, I raised the cathode until I was below 10V, but this way it is only 10mm below surface. I noticed some brownish looking (definitely not grey) "smoke" emanating from the anode. The current is at 6mA, anything below and the voltage goes below 10V again.
Unfortunaely, this way the desired distance between the electrodes has risen considerably and varies over the height. The 37 millimeters are only maintained towards the surface. After 15 minutes, the result is a beautiful yellow.
So you were making about 250ml of24ppm?
10mm cathode distance sounds about right. Without stirring, it only has to touch the water.
While I go and find a .6 mm copper wire, the liquid has changed to deep orange that concentrates around the anode, but no more brownish smoke whiskers.
I throw it away. There is quite a residue on the glas and a slight light umbra deposit on the anode.
I make a new batch with the .6 mm wire, and it clearly goes farther into the liquid, but not much. 2 cm and I have the same conditions as above.
Smoke coming off the anode indicates the anode is too small for your current.
You might try folding your anodes in half so they don't go so far low in the water. Of course, stirring would probably eliminate the problem also.
Another thing, 10 volts is not the target. More than 10 is the target. Try 15 or 20 if possible.
The smoke is caused by the silver exceeding the solubility limit in the boundary layer between the anode and the bulk water. Voltage is what moves the silver ions out of the boundary layer. So more voltage is always beneficial.
If you get plating on the beaker, hydrogen peroxide will remove it unless you let it turn into a mirror.
Some people use an aquarium air pump to keep the solution stirred as a cheap alternative to a magnetic stirrer.
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