Set up electrolysis

Safety

Fix the red cable’s ring terminal to the MMO anode and the black cable’s to the stainless steel cathode. Never swap them. Reversed, the stainless steel cathode corrodes quickly and leaches Cr, Ni and Fe into the culture.

LabCrafter kits

Struck-through items are already done in a LabCrafter kit.

1. Seat the silicone septumThe 2 mm silicone disc in the vial cap. It seals the vial mouth, both electrodes and every needle port, and self-heals needle holes. in the Vial Cap.
2. Push the stainless steel cathodeThe negative electrode: a stainless steel rod. Hydrogen forms on it, so it shows about twice the bubbles of the anode. It must never be wired as the anode. (the rod) up through the septum from below until its top is flush with the top of the cap. Level it with a flat edge.
3. Tighten the thumb screw to hold it in place: firmly, not hard.
4. Repeat with the MMO anodeThe positive electrode: a titanium tube coated with mixed metal oxide (IrO₂-Ta₂O₅). Oxygen forms on it, and CO₂ flows down its bore into the vial. (the tube).
5. Crimp a ring terminal onto each electrode cable.
6. Fix the red cable to the MMO anode: ring terminal, spring washer, then M3 nut.
7. Fix the black cable to the stainless steel cathode the same way.
8. Check both electrode tops are still flush with the cap top.
9. Weigh the dry empty vial and record its weight.
10. Fill it to about 30 ml, the working volume, with nutrient solution or bicarbonate of equal ionic strength.
11. Screw the Vial Cap fully onto the vial, compressing the septum evenly.

Notes

• One septum seals the vial mouth, each electrode and every port, and self-heals sampling-needle tracks. AEP0.2 has no electrode o-rings and no cap o-ring.
• The cap’s column height sets each electrode’s length and protrusion into the vial, so flush tops give every unit the same standard depth.

Parts

• 1×Silicone septum, 2 mm thick, 60 Shore Apart
• 1×Vial cap and electrode holderprinted
• 1×MMO anode, 100 mm long, 6 mm OD, 4 mm ID, 70 mm active lengthpart
• 1×Stainless steel cathode, 100 mm long, 6 mm diameterpart
• 2×Wiring, electrode cablespart
• 2×Ring terminalspart
• 2×M3 nutspart
• 2×M3 spring washerspart
• 2×Thumb screwspart
• 1×Crimp connector (TE Connectivity AMP 1-104479-0)part
• 1×Crimp housing (TE Connectivity AMP 487526-1)part
• 1×Pioreactor 40 ml glass vialearlier step

Tools

• 1×Analytical balancetool

Check your work

1. Which electrode is the red cable's ring terminal fixed to?

   • The stainless steel cathode (the rod)
   • The MMO anode (the tube)
   Show the answer

   Answer: The MMO anode (the tube)

   • If you see The stainless steel cathode (the rod): Swap the two ring terminals now, before anything drives the electrodes. Reversed, the stainless steel corrodes quickly and leaches Cr, Ni and Fe into the culture.

2. With the cap fully screwed on, where are the electrode tops?

   • Both flush with the top of the cap
   • One or both standing proud of the cap top
   • One or both sitting below the cap top
   • Uneven, as the cap will not screw fully on
   Show the answer

   Answer: Both flush with the top of the cap

   • If you see One or both standing proud of the cap top: Push it down through the septumThe 2 mm silicone disc in the vial cap. It seals the vial mouth, both electrodes and every needle port, and self-heals needle holes. until it seats in its journal boreThe close-fitting hole in the vial cap's column that each electrode seats in. The column height sets how far the electrode reaches into the vial., top flush. The cap's column height sets the standard depth.
   • If you see One or both sitting below the cap top: Unscrew the cap, push the electrode up through the septum until its top is flush, and screw the cap back on.
   • If you see Uneven, as the cap will not screw fully on: Check the septum lies flat across the vial mouth so it compresses evenly.

≈ 0.02 g CO₂e per view