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Carbon dioxide in vinyl anaerobic chambers

Image: Vinyl anaerobic chamber, Microbe Research LLC

While monitoring the CO2 level within a newly installed vinyl anaerobic chamber, I noticed a steady loss of CO2 over a period of days that could only have been caused by diffusion of CO2 through the vinyl. This prompted me to model chamber operations over time to better understand the combined effect of CO2 loss from diffusion and CO2 gain from airlock operation.

Here I review some chamber basics, show outcomes of the model, review why CO2 is used in anaerobe chambers, and describe how I monitor and control CO2.

Battery backup power for a small freezer

The following equipment provides me with auto‑switching backup power for a manual defrost "Arctic King" 3.5 CuFt chest-style freezer maintaining a temperature of -24 to -27 degrees C. The system powers the freezer for 61 hours using ~80% of the battery discharge capacity. The freezer draws ~55 watts of power when running (probably ~50% of the time) and briefly more during compressor startup.

  • Lithium-Iron-Phosphate (LiFePO4) battery pack:   "12V OWL MA12V OWL MAX 2 LifePO4 - 228Ah" from BigBattery.Com.
  • Charger:   "PEVO-12V-C12V" from BigBattery.com.
  • Battery-to-inverter cables:   Anderson SB175 gray connector to 5/16 ring lug terminals on 18 inch long 4‑Gauge AWG copper cable from BatteryCablesUSA.com.
  • Power inverter:   12‑volt 600‑watt continuous power sine‑wave inverter.
  • Automatic transfer switch:   Xantrex 808-0915 PROwatt SW Transfer Switch, 15 Amp, 80 millisecond.
  • Two NEMA 5-15 electrical connectors:   3-wire, 15 Amp, one receptacle and one plug.

Retort stand - custom made

This retort stand can support more than a kilogram at the end of a long clamp projecting out opposite from the base. I built this because I prefer to work on the opposite side from the base, which commercial stands are too light to permit. The ballast is five pounds of lead shot. The support rod is 0.5 inch diameter hollow 6063 aluminum with 0.115 inch wall.

Retort stand, custom-made Retort stand, custom-made