[Babcock_Hall]

This is a pedagogical question, and one that I am asking out of curiosity as much as anything.  It is often the case that a crude product is not highly soluble in the developing solvent (we had a thread which focused on dry loading as a way around this problem).  Low-percentage mixtures of ethyl acetate/hexanes come to mind as one example.  Why is the solute soluble enough to pass through the column?  My first explanation is that the solute is only spending a fraction of its time in solution; the rest of the time, it is bound to silica.  My second explanation is that as the solute moves down the column, it becomes more dilute, reducing the solubility problem.  Both explanations could have some truth in them.

[rolnor]

I don't know if your thoughts are valid. But if you work with compounds there are very insoluble, try substitute hexan with toluene or even better, use a mixture of DCM/MeOH, this is a very powerful solvent. You can pack the column with pure DCM, then use a MeOH-gradient. I gave you a Mole Snack Babcock, this is a very important topic, even very skilled chemist have often problem with this issue.