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electrochemistry; this is often referred to as "blanketing" the cell. In general, blanketing is used after solution
purging, where blanketing prevents acquiring new oxygen from the gas above the solution.
Many modern electrochemical test systems include automatic control of gas flow in their experimental
sequencing. This is true of Gamry Instruments' PV and PHE software. These systems generate a digital signal
that is intended to control a solenoid valve, which in turn routes gas flow to the cell. Gamry's VistaShield™
Faraday cage, when equipped with a Purge and Stir option, provides a complete solution for purge gas control.
Pre-saturation of the Purge Gas
Bubbling dry purge gas through your cell electrolyte can cause significant evaporation of the electrolyte's solvent
during the purge process. This can be a significant source of error in some experiments. This problem can often
be avoided by pre-saturation of the purge gas with the solvent prior to it entering the cell. This is commonly
done using a "gas washing bottle," which can be obtained at most laboratory supply companies.
Gas Dispersion Apparatus
In the ParaCell, gas-flow control apparatus is not included. Outlined is one way to handle gas flow. Use a thin
flexible tubing (PTFE or other) for the gas feed line. With the cell assembled, run the feed line in through the
angled, threaded access port on the counter side. Feed through to the bottom of the cell, as near the center as
possible. Leave the top threaded port on the counter side open for venting. You can also use a fritted 6 mm
glass tube for the feed gas, but this is less efficient because of the cell geometry. The cell geometry means that
you must allow extra time for purging in all cases, but particularly if the purging is being done to the side (as
with a fritted gass tube).
When purging, the vent function is critical. Whenever gas is flowing into the cell, you must provide a way for it
leave the cell. If you, do not, the gas may not flow, or worse, the cell may pressurize, which could cause
leaking. Not providing a vent for the escape of purge gas is a very common and potentially hazardous "mistake"
made when setting up an electrochemical cell. There are vent points set high into the end plates which feed
into the top threaded ports. As long as one of those vents is cleared, the cell can vent properly.
Warning:
cell. The ParaCell was not designed to withstand gas pressure! Failure to vent the cell can cause damage to
the cell, uncontrolled loss of electrolyte from the cell, and risk of personal injury to the cell's operator.
AssemblyGas-flow Overview and Terminology
If you use purge of blanket gas, you must provide a vent for the gas to escape the
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