To address a lot of questions about hydrogen safety or leaks in the cell, let's talk about the amount of hydrogen we are filling in the cell.

The glass tube dimensions are:

- Outer diameter: 40.0 mm
- Inner diameter: 35.0 mm
- Length: 300.0 mm

So, the internal volume of the cell is: π⋅r²⋅L = 3.14159 * 0.175² * 3.0 = 0.2886 liters

Then the mica boards are: 3.2 mm x 11.5 mm x 300.0 mm
So the volume of each mica part is: 0.032 x 0.115 x 3.0 = 0.01104 liters
The total volume of the 3 parts of mica is : 3 x 0.01104 = 0.03312 liters

Finally the stainless steel rod in the center of the cell is: ø6.0 mm x 300.0 mm
The volume of the rod is: π⋅r²⋅L = 3.14159 * 0.03² * 3.0 = 0.0085 liters

Thus the available volume inside the cell is: 0.2886 - 0.03312 - 0.0085 = 0.2470 liter = 2.47⋅10^-4 m³

The ideal gas law will give us the number of mole of hydrogen in the cell:

PV = nRT  =>  n = PV / RT

When we load the cell with pure hydrogen at ambient temperature (295 °K) at 3.5 bars we have:

n = 3.5⋅10⁵ Pa * 2.47⋅10^-4 m³ / (8.3144621 J·K⁻¹mol^-1 * 295 °K) = 0.0352 mol

The atomic mass of dihydrogen is: 2.0159 gram / mol

So at maximum, we are filling the cell with: 0.0352 * 2.0159 = 71 milligrams of H2