Mystral

I recently heard about an Einstein packing density equation that has the structure of Øa = Øb*[1-(V/Vmax)]^n I am not sure where this is from and couldn't find such an Einstein formula nor its explanation on the web. Can anyone help to point me in the right direction?

How then do we determine (from millions of available small particles) which crystal/ particle can create this effect, and which will just sink to the bottom without encouraging further bubble formation? Does the chemistry of the particle affect this at all, and if so, what/ how?

Why do certain particles/ crystals, e.g. sugar, encourage the creation of bubbles in beers and stouts when dissolving? I have noticed that when sugar was dropped into stout/ beer, it creates a surge of bubbles (released from gas in beer) to the surface. However, there were 2 other observations made:- 1. dropping non-soluble particles, e.g. silica or sand, do not create this effect. 2. dropping certain soluble particles, e.g. coffee, do not create this effect.