simple column chromatography

[Comandante]

I wanted to be able to separate some organic mixtures at home inexpensively and relatively efficiently so I thought I could make a column chromatography apparatus. Now, I figured that for my purpose I could use either glass or plastic tube (glass preferably) of about 2cm diameter or less, I could also mix up the mobile phase for transfer depending on the separation type and I could use a syringe top to produce some positive pressure, but one thing that I would like to know is this: Assuming that I could use some very fine sand for the stationary phase, I'd like to know what would be the largest particle size that could produce a useful separation and how long would the tube need to be to match this?