Having done some pilot scale experiments (60 l barrels), I’ve noticed that mixers are absolutely essential. At that scale, metals really do form notable concentration gradients.
solid metals are a separate phase, they create a deposit
salts over a certain concentration, part create a deposit, so they slowly create a powder at the bottom, part stay in solution as ions
Ionic metal in solutions spreads all over, as any concentration difference (gradient) generates an excess of free energy that the system naturally releases. You need to add external energy to maintain the gradient, such as a external electric potential gradient (an anode and a cathode)
Generally speaking, the experiments should follow the third category, but the system didn’t have enough time to reach equilibrium.
If you have infinite time at your disposal, you can rely on diffusion to do its job. Unfortunately, the project had a finite amount of time allocated to it, and 60 l barrels are large enough that significant concentration gradients can exist. Found that out the hard way.
LPT: Don’t start your experiments until all the mixers have arrived.
Having done some pilot scale experiments (60 l barrels), I’ve noticed that mixers are absolutely essential. At that scale, metals really do form notable concentration gradients.
It depends on their form:
solid metals are a separate phase, they create a deposit
salts over a certain concentration, part create a deposit, so they slowly create a powder at the bottom, part stay in solution as ions
Ionic metal in solutions spreads all over, as any concentration difference (gradient) generates an excess of free energy that the system naturally releases. You need to add external energy to maintain the gradient, such as a external electric potential gradient (an anode and a cathode)
Generally speaking, the experiments should follow the third category, but the system didn’t have enough time to reach equilibrium.
If you have infinite time at your disposal, you can rely on diffusion to do its job. Unfortunately, the project had a finite amount of time allocated to it, and 60 l barrels are large enough that significant concentration gradients can exist. Found that out the hard way.
LPT: Don’t start your experiments until all the mixers have arrived.