A look at Faraday Efficiency:
.627 Liters per hour per amp is representative of 100% Faraday
Efficiency at 32oF and 1 atm pressure.
The ratio of .627 liters
per hour per amp is the
same thing as .627 divided by 60 minutes to get .01045 liters
per minute per amp and
then, because there are 1000 milliliters in a liter, multiplied by 1000
to get 10.45 milliliters per
minute per amp.
So, let's take another short look at how we can get there.
First, we can perform the calculation for the half reaction for Hydrogen
in the electrolysis of water to find it's theoretical
volume produced per minute per amp.
Electrical Charge in Coulombs (C) = t X I (60 seconds X 1 Amp) = 60 C
The volume of Hydrogen, or any gas for that matter, per mole is a given
value. At standard pressure and temperature, the volume of Hydrogen per
mole is 22.414 Liters or 22,414 Milliliters which, by the way, is the
Ideal Gas Constant (0.0820574587) multiplied by the Standard Temperature
in Kelvins (273.15 K which is equal to 0 C or 32 F). Also, this is the
point in the calculation where temperature corrections are made to
adjust the volume per mole.
For example, many people will use what is commonly referred to as "room
temperature" (25 C = 77 F
= 298 K) to make these
calculations which makes the volume of gas per mole = Ideal Gas Constant
(0.0820574587) multiplied by room temperature in Kelvins (298 K) =
24.4531226926 Liters or 24,453 Milliliters per mole. In order to make
this more clear, I will carry out this example throughout these
Anyway, 1 mole of Hydrogen yields 2 moles of electrons.
The electrical charge of one mole of electrons (Faraday's Constant) is
given as 96,485 C (1 Faraday). Since we have two moles of electrons, the
electrical charge delivered by one mole of Hydrogen = 2 X 96,485 C or
Hydrogen volume = Electrical charge in Coulombs (60
C) / (divided by) Electrical
charge delivered by one mole of Hydrogen (192,970
C) X (multiplied by) Hydrogen
Volume per mole (22,414
milliliters or 24,453 milliliters at room temperature ) =
60 C / 192,970 C = .000311
.000311 X 22,414 = 6.97 milliliters
Or, at room temperature (298 K)
.000311 X 24,453 = 7.60
Hydroxy contains 100% more Hydrogen than Oxygen, so we need to add 50%
of 6.29 which brings us up to 10.45 milliliters. Okay, let's verify that
again by performing the calculations for the other half reaction for
Oxygen and adding it to our results for Hydrogen.
Instead of 2 moles of electrons like we had for Hydrogen, we have 4
moles of electrons for Oxygen, so 4 X 96,485 C = 385,940 C/mole.
60 C / 385,940 C = 0.000155
0.000155 X 22,414 = 3.48 milliliters of Oxygen
Or, at room temperature (298 K):
.000155 X 24,453 = 3.80
6.97 milliliters Hydrogen + 3.48 milliliters Oxygen = 10.45 milliliters
of Hydroxy per minute per amp per cell.
Or, at room temperature (298 K):
7.60 milliliters Hydrogen + 3.80 milliliters Oxygen = 11.4
Hydroxy per minute per amp per cell.
To correct for pressure, you just divide that final number by the
atmospheric pressure represented in units of atm (atmospheres). Most
local weather stations report atmospheric pressure in millibars or
hectopascals (both the same thing). You can convert that to atmospheres
by multiplying the value given in millibars or hectopascals by
That's the nub of it!