Why so much electrolyte?

[schiaucu]

In my settings i use 4 mA of current at 30V, the electrodes spacing is 5.5 cm and I use 0.5 mol/l sollution of sodium carbonate as electrolyte.
In my logic, the electrolyte is used to break the resistivity of distilled water in order to have a constant current. So I have noticed that for 300 ml of distilled water, one or two drops of electrolyte gives me enough condutivity to reach a current of 4mA. Every extra drop of electrolyte only gives me smaller values of the voltage across the cell. So my question is: Why all that extra electrolyte? What is the reason to add 12 drops of 0.5 mol/l of electrolyte, and how you can manage the voltage?

[kephra]

More electrolyte = less plateout and using the recommended amount puts the pH in its optimal sweet spot of 8.5
You manage the voltage by adjusting the amount of cathode in the water.  Less cathode = higher voltage.
Its not just about making the water conductive.

[schiaucu]

Roger Alpha, thank you!

[schiaucu]

So I assume that less plating on the cathode means more silver in the solution and less silver waste in oxides.

[schiaucu]

Today I did a little experiment using just distilled water and no electrolyte, at 30V limited at 4mA, silver anode, silver cathode, electrode spacing 5.5 cm, no heat, just stirring.
Every 15 min I’ve made readings with the tds meter and compared them with the estimations using the Faraday law. The difference was huge (50ppm estimated vs. 15ppm actual readings) and I believe that the difference is in fact the silver oxide plated on the cathode (that I had to wipe it several times during the entire process).

Here is the graphic that I made.

[kephra]

Nice graph!
The point where your current suddenly flattened out is probably the point at which you reached silver oxide saturation.  This would have been at an actual 20 to 25 ppm depending on temperature.

So I assume that less plating on the cathode means more silver in the solution and less silver waste in oxides.

The wasted silver is metallic silver, not oxides, collected on the cathode.

TDS readings do not read silver correctly.

[schiaucu]

So the black fluffy dust on the cathode is metallic silver?

[schiaucu]

Do you think that the actual 15ppm reading on the tds was in reality 20ppm? notice the Tyndall effect, it became present after 165 minutes and the water was at room temp. (22°C).
Na+ does carry more or less current than Ag+?

[Gene]

TDS meters are designed to read the quality of tap water (distilled works also).  They will not accurately read the PPM of ionic silver and you will get a reading for colloidal silver but since colloidal form is a suspension (silver nanoparticles floating in water) where nothing is dissolved you can immediately see how they don't work for reading silver. The only correct reading for colloidal silver is ZERO! Oh, and the electrodes on TDS meters are usually silver plated.  Hmmm!

Regarding the electrolyte, you need the correct amount (which would be 18-20 drops per liter) so the cell functions properly (yes, partly to increase conductivity of the water which is a nearly perfect insulator without it) but also for after the run so the finished ionic silver is in the alkaline range so the reducing sugar opens up into its reducing form and actually reduces the silver oxide dissolved in the water (what ionic silver is) into suspended silver nanoparticles (what colloidal silver is).

Silver oxide does not plate on the cathode. Pure silver does.  When the plating happens, the oxygen splits from the silver oxide and only the silver is deposited. Thats why you see bubbles.  But with electrolyte in the cell you see bubbles for a different reason.  Kephra has explained this in another document on this site you can search for explaining the exact chemistry involved.

That grayish black stuff that forms on the anode during a run is in fact silver oxide that hasn't mobilized yet into the water and dissolved into solution.

I have no clue what the black stuff you saw on the silver cathode was for you not using any electrolyte.  I seriously doubt you had anything close to 4ma flowing given there was no electrolyte.  Just because you limited the current to 4ma doesn't mean thats what you're getting.  You need to measure it with a multimeter to see what it really is.

Pure distilled water is almost a complete electrical insulator.  If you really didn't add any electrolyte I doubt you barely had ANY current flowing at all and if you did get a reasonable current there was something else in that cell beyond the distilled water. Yes, over time the current will increase as you pull tiny amounts of silver oxide into the water and it dissolves but the process is horridly slow without electrolyte and you will get silver plating on the cathode because there isn't any electrolyte present to interfere and prevent the plate-out.

[schiaucu]

If you look at the graph, you will understand. The process started at 0.23mA and ended after 165min. at 3.2mA, never reached the limit of 4mA. And I still not have a good explanation of why the tds meter is not good for reading ionic silver. (not colloidal).

[kephra]

TDS meters read conductivity, thats all they read.  They do not know what causes the conductivity.  Since ppm is the weight of one substance divided by the weight of another, and the weight of each element is different, a TDS meter is not calibrated for silver.  Conductivity also depends on the valence of the atoms, and the temperature of the water.  I thoroughly explained this already in the Articles section.

Also note that the Tyndall effect is not an instantaneous effect like turning on a switch.  The actual precipitation of the silver oxide begins before there is enough in the water to actually notice.