I just realized my first paragraph in the first post was a bit confusing, when I said "positive of the power supply" and "negative of the power supply" I meant positive of the current limiter and negative of the power supply.
The current limiter doesn’t have a negative output, only positive coming from the power supply. I don’t see how it could have a negative as the LM317 and the potentiometer only allows for voltage in. Lm317 Vin from the power source, Vout from the LM317, (still positive) to the potentiometer and resistors and from there to an alligator clip. So I am not sure how I can connect it to the meter as you described. The only way without connecting it to a cell is; positive from the current limiter --> positive probe of the meter and negative from the power supply --> negative of the meter. Maybe I am confused about the terminology here.
The power supply is 24 volts, so it does have that 3V headroom needed, which is why when I connect it directly to the current limiter and take a voltage reading it shows as 21-22 volts.
That was the odd thing with the last run I did, I was expecting to see the voltage change as I moved the depth of the cathode. But it didn’t have any really noticeable changes like it did before. Before I could barely put the cathode in the water and it would drastically drop the voltage. But this might be because the room temperature water has more resistance then water at 60-80c. Which, as a side note, is an odd property of water and conductivity, I thought generally as you cool electrical connections resistance is lowered. Which is why superconductors need to be supercooled with helium or nitrogen etc.
The particular LM317 I have can go as low as 2.5ma according to the spec sheet (if I recall correctly), but its more likely to be around 3ma. And it definitely can go below 10ma, because I tested that by taking a reading with the meter in the cell with it hooked up properly, the lowest I got was 4ma, briefly playing around with it.
The limiter is fairly stable as it doesn’t adjust much at all unless the properties of the cells solution change, temperature, stirring, heat etc. I’m just confused as to what current to use for the calculations.
The way you describe hooking up the limiter to the cell is how I’ve been doing it, output of the LM317 (which I thought was positive, when attached to the meter – limiter output --> positive meter probe – power supply negative --> meter negative probe, it shows a positive voltage). So attached to the cell it’s, power supply positive --> limiter input --> limiter output --> anode (silver) and negative of power supply --> cathode (copper).
So the problem I am seeing is, when the limiter is connected to the cell it gets a different reading as to when it’s connected to just the meter. For example, I can get a stable 15ma with it connected to just the meter, but when its connected to the cell and the meter is attached the way you described I get 6-7ma, which can then further drop 0.5-1ma with stirring. This has lead me to question if I was able to correctly take an initial current reading of the limiter or if I was reading the current in the cell correctly in the first place, which I wasn't.
Sorry for the long reply, I really do appreciate the time, help and well thought out responses you are giving me and have given me in the past.
Thank you